GitHub CLI (gh) is GitHub’s official command line tool. Prior to 2.93.0, GitHub CLI incorrectly includes authorization header in API requests to TUF repository mirrors via gh attestation, gh release verify, and gh release verify-asset commands. The CLI uses a shared HTTP client with an authentication layer that automatically attaches tokens to outgoing requests. This layer lacks accurate host detection and can incorrectly attribute the target host, providing it with a token it should never receive. Specifically, the host normalization logic collapses any *.github.com subdomain to github.com, so a request to tuf-repo.github.com (a GitHub Pages site, not a GitHub API endpoint) is treated as a request to github.com and receives the user's github.com token. For hosts that don't match github.com or a known GHES instance at all, the resolver falls back to GH_ENTERPRISE_TOKEN if set. The gh attestation, gh release verify and gh release verify-asset commands fetch data from several external hosts as part of their normal operation (TUF metadata from tuf-repo.github.com and tuf-repo-cdn.sigstore.dev, artifact bundles from Azure Blob Storage). Because these requests go through the same authenticated HTTP client, the token is sent to all of them. This vulnerability is fixed in 2.93.0.

Gitsign is a keyless Sigstore to signing tool for Git commits with your a GitHub / OIDC identity. From 0.4.0 to before 0.15.0, CertVerifier.Verify() in pkg/git/verifier.go unconditionally dereferences certs[0] after sd.GetCertificates() without checking the slice length. A CMS/PKCS7 signed message with an empty certificate set is a structurally valid DER payload; GetCertificates() returns an empty slice with no error, causing an immediate index-out-of-range panic. On the gitsign --verify code path (the GPG-compatible mode invoked by git verify-commit), the panic is silently recovered by internal/io/streams.go's Wrap() function, which returns nil instead of an error. main.go then exits with code 0, causing exit-code-only verification callers to interpret the failed verification as success. This vulnerability is fixed in 0.15.0.

Gitsign is a keyless Sigstore to signing tool for Git commits with your a GitHub / OIDC identity. Prior to 0.16.0, gitsign verify and gitsign verify-tag re-encode commit/tag objects through go-git's EncodeWithoutSignature before checking the signature, instead of verifying against the raw git object bytes. For malformed objects with duplicate tree headers, git-core and go-git parse different trees: git-core uses the first, go-git uses the second. A signature crafted over the go-git-normalized form (second tree) passes gitsign verify while git-core resolves the commit to a completely different tree. This breaks the invariant that a verified signature, the commit semantics git-core presents to users, and the object hash logged in Rekor all refer to the same content. This vulnerability is fixed in 0.16.0.

Sigstore Timestamp Authority is a service for issuing RFC 3161 timestamps. Versions 2.0.5 and below contain an authorization bypass vulnerability in the VerifyTimestampResponse function. VerifyTimestampResponse correctly verifies the certificate chain signature, but the TSA-specific constraint checks in VerifyLeafCert uses the first non-CA certificate from the PKCS#7 certificate bag instead of the leaf certificate from the verified chain. An attacker can exploit this by prepending a forged certificate to the certificate bag while the message is signed with an authorized key, causing the library to validate the signature against one certificate but perform authorization checks against another. This vulnerability only affects users of the timestamp-authority/v2/pkg/verification package and does not affect the timestamp-authority service itself or sigstore-go. The issue has been fixed in version 2.0.6.

linuxfoundation

sigstore-ruby is a pure Ruby implementation of the sigstore verify command from the sigstore/cosign project. Prior to 0.2.3, Sigstore::Verifier#verify does not propagate the VerificationFailure returned by verify_in_toto when the artifact digest does not match the digest in the in-toto attestation subject. As a result, verification of DSSE bundles containing in-toto statements returns VerificationSuccess regardless of whether the artifact matches the attested subject. This vulnerability is fixed in 0.2.3.

sigstore

Cosign provides code signing and transparency for containers and binaries. In versions 3.0.4 and below, an issuing certificate with a validity that expires before the leaf certificate will be considered valid during verification even if the provided timestamp would mean the issuing certificate should be considered expired. When verifying artifact signatures using a certificate, Cosign first verifies the certificate chain using the leaf certificate's "not before" timestamp and later checks expiry of the leaf certificate using either a signed timestamp provided by the Rekor transparency log or from a timestamp authority, or using the current time. The root and all issuing certificates are assumed to be valid during the leaf certificate's validity. There is no impact to users of the public Sigstore infrastructure. This may affect private deployments with customized PKIs. This issue has been fixed in version 3.0.5.

sigstore

sigstore-python is a Python tool for generating and verifying Sigstore signatures. Prior to version 4.2.0, the sigstore-python OAuth authentication flow is susceptible to Cross-Site Request Forgery. `_OAuthSession` creates a unique "state" and sends it as a parameter in the authentication request but the "state" in the server response seems not not be cross-checked with this value. Version 4.2.0 contains a patch for the issue.

linuxfoundation

sigstore framework is a common go library shared across sigstore services and clients. In versions 1.10.3 and below, the legacy TUF client (pkg/tuf/client.go) supports caching target files to disk. It constructs a filesystem path by joining a cache base directory with a target name sourced from signed target metadata; however, it does not validate that the resulting path stays within the cache base directory. A malicious TUF repository can trigger arbitrary file overwriting, limited to the permissions that the calling process has. Note that this should only affect clients that are directly using the TUF client in sigstore/sigstore or are using an older version of Cosign. Public Sigstore deployment users are unaffected, as TUF metadata is validated by a quorum of trusted collaborators. This issue has been fixed in version 1.10.4. As a workaround, users can disable disk caching for the legacy client by setting SIGSTORE_NO_CACHE=true in the environment, migrate to https://github.com/sigstore/sigstore-go/tree/main/pkg/tuf, or upgrade to the latest sigstore/sigstore release.

Sigstore Timestamp Authority is a service for issuing RFC 3161 timestamps. Prior to 2.0.3, Function api.ParseJSONRequest currently splits (via a call to strings.Split) an optionally-provided OID (which is untrusted data) on periods. Similarly, function api.getContentType splits the Content-Type header (which is also untrusted data) on an application string. As a result, in the face of a malicious request with either an excessively long OID in the payload containing many period characters or a malformed Content-Type header, a call to api.ParseJSONRequest or api.getContentType incurs allocations of O(n) bytes (where n stands for the length of the function's argument). This vulnerability is fixed in 2.0.3.

linuxfoundation

sigstore-python is a Python tool for generating and verifying Sigstore signatures. Versions of sigstore-python newer than 2.0.0 but prior to 3.6.0 perform insufficient validation of the "integration time" present in "v2" and "v3" bundles during the verification flow: the "integration time" is verified *if* a source of signed time (such as an inclusion promise) is present, but is otherwise trusted if no source of signed time is present. This does not affect "v1" bundles, as the "v1" bundle format always requires an inclusion promise. Sigstore uses signed time to support verification of signatures made against short-lived signing keys. The impact and severity of this weakness is *low*, as Sigstore contains multiple other enforcing components that prevent an attacker who modifies the integration timestamp within a bundle from impersonating a valid signature. In particular, an attacker who modifies the integration timestamp can induce a Denial of Service, but in no different manner than already possible with bundle access (e.g. modifying the signature itself such that it fails to verify). Separately, an attacker could upload a *new* entry to the transparency service, and substitute their new entry's time. However, this would still be rejected at validation time, as the new entry's (valid) signed time would be outside the validity window of the original signing certificate and would nonetheless render the attacker auditable.

sigstore-java is a sigstore java client for interacting with sigstore infrastructure. sigstore-java has insufficient verification for a situation where a bundle provides a invalid signature for a checkpoint. This bug impacts clients using any variation of KeylessVerifier.verify(). Currently checkpoints are only used to ensure the root hash of an inclusion proof was provided by the log in question. Failing to validate that means a bundle may provide an inclusion proof that doesn't actually correspond to the log in question. This may eventually lead a monitor/witness being unable to detect when a compromised logs are providing different views of themselves to different clients. There are other mechanisms right now that mitigate this, such as the signed entry timestamp. Sigstore-java currently requires a valid signed entry timestamp. By correctly verifying the signed entry timestamp we can make certain assertions about the log signing the log entry (like the log was aware of the artifact signing event and signed it). Therefore the impact on clients that are not monitors/witnesses is very low. This vulnerability is fixed in 1.2.0.

sigstore-java is a sigstore java client for interacting with sigstore infrastructure. sigstore-java has insufficient verification for a situation where a validly-signed but "mismatched" bundle is presented as proof of inclusion into a transparency log. This bug impacts clients using any variation of KeylessVerifier.verify(). The verifier may accept a bundle with an unrelated log entry, cryptographically verifying everything but fails to ensure the log entry applies to the artifact in question, thereby "verifying" a bundle without any proof the signing event was logged. This allows the creation of a bundle without fulcio certificate and private key combined with an unrelated but time-correct log entry to fake logging of a signing event. A malicious actor using a compromised identity may want to do this to prevent discovery via rekor's log monitors. The signer's identity will still be available to the verifier. The signature on the bundle must still be on the correct artifact for the verifier to pass. sigstore-gradle-plugin and sigstore-maven-plugin are not affected by this as they only provide signing functionality. This issue has been patched in v1.1.0 release with PR #856. All users are advised to upgrade. There are no known workarounds for this vulnerability.

Gitsign is a keyless Sigstore to signing tool for Git commits with your a GitHub / OIDC identity. gitsign may select the wrong Rekor entry to use during online verification when multiple entries are returned by the log. gitsign uses Rekor's search API to fetch entries that apply to a signature being verified. The parameters used for the search are the public key and the payload. The search API returns entries that match either condition rather than both. When gitsign's credential cache is used, there can be multiple entries that use the same ephemeral keypair / signing certificate. As gitsign assumes both conditions are matched by Rekor, there is no additional validation that the entry's hash matches the payload being verified, meaning that the wrong entry can be used to successfully pass verification. Impact is minimal as while gitsign does not match the payload against the entry, it does ensure that the certificate matches. This would need to be exploited during the certificate validity window (10 minutes) by the key holder.

sigstore-go, a Go library for Sigstore signing and verification, is susceptible to a denial of service attack in versions prior to 0.6.1 when a verifier is provided a maliciously crafted Sigstore Bundle containing large amounts of verifiable data, in the form of signed transparency log entries, RFC 3161 timestamps, and attestation subjects. The verification of these data structures is computationally expensive. This can be used to consume excessive CPU resources, leading to a denial of service attack. TUF's security model labels this type of vulnerability an "Endless data attack," and can lead to verification failing to complete and disrupting services that rely on sigstore-go for verification. This vulnerability is addressed with sigstore-go 0.6.1, which adds hard limits to the number of verifiable data structures that can be processed in a bundle. Verification will fail if a bundle has data that exceeds these limits. The limits are 32 signed transparency log entries, 32 RFC 3161 timestamps, 1024 attestation subjects, and 32 digests per attestation subject. These limits are intended to be high enough to accommodate the vast majority of use cases, while preventing the verification of maliciously crafted bundles that contain large amounts of verifiable data. Users who are vulnerable but unable to quickly upgrade may consider adding manual bundle validation to enforce limits similar to those in the referenced patch prior to calling sigstore-go's verification functions.

sigstore

Minder by Stacklok is an open source software supply chain security platform. Minder prior to version 0.0.51 is vulnerable to a denial-of-service (DoS) attack which could allow an attacker to crash the Minder server and deny other users access to it. The root cause of the vulnerability is that Minders sigstore verifier reads an untrusted response entirely into memory without enforcing a limit on the response body. An attacker can exploit this by making Minder make a request to an attacker-controlled endpoint which returns a response with a large body which will crash the Minder server. Specifically, the point of failure is where Minder parses the response from the GitHub attestations endpoint in `getAttestationReply`. Here, Minder makes a request to the `orgs/$owner/attestations/$checksumref` GitHub endpoint (line 285) and then parses the response into the `AttestationReply` (line 295). The way Minder parses the response on line 295 makes it prone to DoS if the response is large enough. Essentially, the response needs to be larger than the machine has available memory. Version 0.0.51 contains a patch for this issue. The content that is hosted at the `orgs/$owner/attestations/$checksumref` GitHub attestation endpoint is controlled by users including unauthenticated users to Minders threat model. However, a user will need to configure their own Minder settings to cause Minder to make Minder send a request to fetch the attestations. The user would need to know of a package whose attestations were configured in such a way that they would return a large response when fetching them. As such, the steps needed to carry out this attack would look as such: 1. The attacker adds a package to ghcr.io with attestations that can be fetched via the `orgs/$owner/attestations/$checksumref` GitHub endpoint. 2. The attacker registers on Minder and makes Minder fetch the attestations. 3. Minder fetches attestations and crashes thereby being denied of service.

Gitsign is software for keyless Git signing using Sigstore. In versions of gitsign starting with 0.6.0 and prior to 0.8.0, Rekor public keys were fetched via the Rekor API, instead of through the local TUF client. If the upstream Rekor server happened to be compromised, gitsign clients could potentially be tricked into trusting incorrect signatures. There is no known compromise the default public good instance (`rekor.sigstore.dev`) - anyone using this instance is unaffected. This issue was fixed in v0.8.0. No known workarounds are available.

sigstore

Cosign is a sigstore signing tool for OCI containers. Cosign is susceptible to a denial of service by an attacker controlled registry. An attacker who controls a remote registry can return a high number of attestations and/or signatures to Cosign and cause Cosign to enter a long loop resulting in an endless data attack. The root cause is that Cosign loops through all attestations fetched from the remote registry in pkg/cosign.FetchAttestations. The attacker needs to compromise the registry or make a request to a registry they control. When doing so, the attacker must return a high number of attestations in the response to Cosign. The result will be that the attacker can cause Cosign to go into a long or infinite loop that will prevent other users from verifying their data. In Kyvernos case, an attacker whose privileges are limited to making requests to the cluster can make a request with an image reference to their own registry, trigger the infinite loop and deny other users from completing their admission requests. Alternatively, the attacker can obtain control of the registry used by an organization and return a high number of attestations instead the expected number of attestations. The issue can be mitigated rather simply by setting a limit to the limit of attestations that Cosign will loop through. The limit does not need to be high to be within the vast majority of use cases and still prevent the endless data attack. This issue has been patched in version 2.2.1 and users are advised to upgrade.

sigstore

Cosign is a project under the sigstore organization which aims to make signatures invisible infrastructure. In versions prior to 1.12.0 a number of vulnerabilities have been found in cosign verify-blob, where Cosign would successfully verify an artifact when verification should have failed. First a cosign bundle can be crafted to successfully verify a blob even if the embedded rekorBundle does not reference the given signature. Second, when providing identity flags, the email and issuer of a certificate is not checked when verifying a Rekor bundle, and the GitHub Actions identity is never checked. Third, providing an invalid Rekor bundle without the experimental flag results in a successful verification. And fourth an invalid transparency log entry will result in immediate success for verification. Details and examples of these issues can be seen in the GHSA-8gw7-4j42-w388 advisory linked. Users are advised to upgrade to 1.12.0. There are no known workarounds for these issues.

sigstore

Cosign provides container signing, verification, and storage in an OCI registry for the sigstore project. Prior to version 1.5.2, Cosign can be manipulated to claim that an entry for a signature exists in the Rekor transparency log even if it doesn't. This requires the attacker to have pull and push permissions for the signature in OCI. This can happen with both standard signing with a keypair and "keyless signing" with Fulcio. If an attacker has access to the signature in OCI, they can manipulate cosign into believing the entry was stored in Rekor even though it wasn't. The vulnerability has been patched in v1.5.2 of Cosign. The `signature` in the `signedEntryTimestamp` provided by Rekor is now compared to the `signature` that is being verified. If these don't match, then an error is returned. If a valid bundle is copied to a different signature, verification should fail. Cosign output now only informs the user that certificates were verified if a certificate was in fact verified. There is currently no known workaround.

sigstore