GitHub CLI (gh) is GitHub’s official command line tool. (CVE-2026-64655)

The GitHub CLI (gh) tool before version 2.97.0 improperly constructs the certificate Subject Alternative Name matcher from the --signer-repo and --signer-workflow flags by not escaping regex metacharacters. Since GitHub allows characters like '.' in organization, repository, and workflow names, these characters act as regex wildcards. An attacker can exploit this by registering a lookalike repository or workflow name that matches the regex pattern intended for a different trusted signer, thereby bypassing Sigstore attestation verification. Exploitation requires the attacker to produce valid attestations from the lookalike repository, which could compromise supply chain trust mechanisms. This vulnerability is addressed in version 2.97.0.

An attacker who can create a plausible lookalike repository and produce valid attestations from it can bypass the intended Sigstore attestation verification. This undermines supply chain verification for CI/CD pipelines or policy gates that rely on pinned trust to specific signing workflows. There is no indication of known exploits in the wild.

Upgrade GitHub CLI (gh) to version 2.97.0 or later, where this issue is fixed. No other mitigation is indicated or required according to the available data.