github.com/sigstore/cosign: Cosign verification accepts any valid Rekor entry under certain conditions (CVE-2026-22703)

Overview

A data verification flaw has been discovered in the golang cosign library. A Cosign bundle can be crafted to successfully verify an artifact even if the embedded Rekor entry does not reference the artifact's digest, signature or public key. When verifying a Rekor entry, Cosign verifies the Rekor entry signature, and also compares the artifact's digest, the user's public key from either a Fulcio certificate or provided by the user, and the artifact signature to the Rekor entry contents. Without these comparisons, Cosign would accept any response from Rekor as valid. A malicious actor that has compromised a user's identity or signing key could construct a valid Cosign bundle by including any arbitrary Rekor entry, thus preventing the user from being able to audit the signing event. This vulnerability only affects users that provide a trusted root via --trusted-root or when fetched automatically from a TUF repository, when no trusted key material is provided via SIGSTORE_REKOR_PUBLIC_KEY. When using the default flag values in Cosign v3 to sign and verify (--use-signing-config=true and --new-bundle-format=true for signing, --new-bundle-format=true for verification), users are unaffected. Cosign v2 users are affected using the default flag values.

Vendor advisories

• Red Hat VEX · Moderate · affected: OpenShift Pipelines, OpenShift Serverless, Red Hat Advanced Cluster Security 4, Red Hat OpenShift Dev Spaces, Red Hat Trusted Artifact Signer, Red Hat Web Terminal, … · no fix planned: OpenShift Pipelines, OpenShift Serverless, Red Hat Advanced Cluster Security 4, Red Hat OpenShift Dev Spaces, … · updated 2026-09-23 · vex

github.com/sigstore/cosign: Cosign verification accepts any valid Rekor entry under certain conditions — rated Moderate by Red Hat. Released 2026-01-10, updated 2026-09-23.

Affected:

• OpenShift Pipelines
• OpenShift Serverless
• Red Hat Advanced Cluster Security 4
• Red Hat OpenShift Dev Spaces
• Red Hat Trusted Artifact Signer
• Red Hat Web Terminal
• Security Profiles Operator
• Zero Trust Workload Identity Manager
• Zero Trust Workload Identity Manager - Tech Preview

No fix planned:

• OpenShift Pipelines
• OpenShift Serverless
• Red Hat Advanced Cluster Security 4
• Red Hat OpenShift Dev Spaces
• Red Hat Trusted Artifact Signer
• Red Hat Web Terminal
• Security Profiles Operator
• Zero Trust Workload Identity Manager
• Zero Trust Workload Identity Manager - Tech Preview

Remediation

Fix deferred

Workarounds / mitigations:

• Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base or stability.

Package advisory (CVE-2026-22703)

Affected packages:

• github.com/sigstore/cosign/v3 < 3.0.4
• github.com/sigstore/cosign/v2 < 2.6.2

Patched in:

• github.com/sigstore/cosign/v3 3.0.4
• github.com/sigstore/cosign/v2 2.6.2

Source: https://osv.dev/vulnerability/GHSA-whqx-f9j3-ch6m