# CVE-2026-64655: GitHub CLI: Attestation Verification Bypass via Unescaped Regex Metacharacters in SAN Matching

CVE-2026-64655 is fixed in 2 products on 2 platforms, first by GitHub CLI 2.97.0, released July 31, 2026. It is not reported as exploited. Patch Radar priority: Routine.

- Web page: https://patchblox.com/security/cve/CVE-2026-64655
- Priority: Routine
- CVSS: 2.1 (Low)
- EPSS: 0.0034
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Aug 6, 2026
- Weakness: Incorrect Regular Expression
- Vendor advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-64655

## 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.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Windows apps | GitHub CLI | 2.97.0 | [GitHub CLI 2.97.0](https://patchblox.com/security/data/fix/windows-app/github.cli-2.97.0.md) | Jul 31, 2026 |
| Linux | gh opensuse-leap 16.0 | 2.98.0-bp160.1.1 | [OPENSUSE-SU-2026:21663-1](https://patchblox.com/security/data/fix/linux/opensuse-su-2026-21663-1.md) | Aug 26, 2026 |

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Data as of 2026-11-08T06:59:42Z UTC. Source: Patchblox Patch Radar (https://patchblox.com/security/patch-radar). Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo

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