CVE-2026-64655: cli Incorrect Regular Expression

Vulnerability summary

CVE-2026-64655 is a low (CVSS 2.1) Incorrect Regular Expression vulnerability in cli. EPSS estimates a 0.34% chance of exploitation in the next 30 days, higher than 26.3% of scored vulnerabilities.

Timeline

1. 06-08-2026
   PublishedVulnerability first disclosed.
2. 08-08-2026
   Last modifiedVulnerability information updated.

Description

GitHub CLI (gh) is GitHub’s official command line tool. Prior to 2.97.0, gh attestation verify  builds the certificate Subject Alternative Name matcher from the --signer-repo and --signer-workflow  flag values without escaping regex metacharacters, so a user-supplied repository or workflow name is treated as a regular expression rather than a literal string. Because GitHub permits characters such as  `.`  in organization, repository, and workflow path names and  `.`  is a regex wildcard, an attacker can register a lookalike name (for example github/artifact.attestations-workflows) that satisfies a matcher intended for a different trusted signer (github/artifact-attestations-workflows), bypassing the intended Sigstore attestation verification. Exploitation requires the attacker to create a plausible lookalike repository and produce valid attestations from it, which could undermine supply chain verification for CI/CD pipelines or policy gates that pin trust to a specific signing workflow. This issue is fixed in version 2.97.0.

• CWE-185Incorrect Regular ExpressionThe product specifies a regular expression in a way that causes data to be improperly matched or compared.