CVE-2026-22703 Details

A vulnerability in Cosign's handling of Rekor entries can lead to incorrect verification of signed artifacts. This issue is present in Cosign versions 2.6.1 and prior, as well as 3.0.3 and prior. The vulnerability arises because Cosign can be tricked into accepting a bundle as valid, even when the associated Rekor entry lacks crucial references to the artifact's digest, signature, or public key. Normally, Cosign performs a thorough verification by comparing these elements against the Rekor entry. However, in the vulnerable versions, this verification can be bypassed, allowing a malicious actor who has compromised a user's identity or signing key to create a fraudulent Cosign bundle. This manipulation would prevent the user from accurately auditing the signing event. The issue primarily affects users who provide a trusted root either manually or through a TUF repository, without supplying their own trusted key material. In contrast, users of Cosign v3 with default settings for signing and verification are not affected.

Upgrade to Cosign versions 2.6.2 or 3.0.4. For users of Cosign v2, the default flag values are vulnerable, while Cosign v3 users are not affected with the defaults. If an immediate upgrade is not possible, trusted key material can be provided using the `SIGSTORE_REKOR_PUBLIC_KEY` environment variable when verifying, which will bypass the vulnerability.