CVE-2026-64655

Received Received - Intake

Regex Bypass in GitHub CLI Attestation Verification

Publication date: 2026-08-06

Last updated on: 2026-08-06

Assigner: GitHub, Inc.

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.

CVSS Scores

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Meta Information

Published

2026-08-06

Last Modified

2026-08-06

Generated

2026-08-07

AI Q&A

2026-08-07

EPSS Evaluated

N/A

NVD

CVE-2026-64655

Affected Vendors & Products

Vendor	Product	Version / Range
github	gh	to 2.97.0 (exc)

Helpful Resources

Exploitability

CWE

KEV

CWE ID	Description
CWE-185	The product specifies a regular expression in a way that causes data to be improperly matched or compared.

Attack-Flow Graph

Executive Summary

This vulnerability affects GitHub CLI (gh) versions before 2.97.0. It involves improper handling of repository and workflow names during attestation verification. The tool treats user-supplied names as regex patterns instead of literal strings, allowing attackers to bypass verification using lookalike names with regex metacharacters like dots.

Detection Guidance

This vulnerability is specific to GitHub CLI (gh) version 2.97.0 or earlier. To detect it, check the installed version of gh using the command: gh version. If the version is less than 2.97.0, the system is vulnerable.

Impact Analysis

If exploited, this vulnerability could allow attackers to bypass Sigstore attestation verification in CI/CD pipelines or policy gates. This undermines supply chain security by enabling malicious code to appear as if it was signed by a trusted source, potentially leading to unauthorized or malicious software being deployed.

Mitigation Strategies

Upgrade GitHub CLI to version 2.97.0 or later using the command: gh upgrade. Alternatively, download the latest version from GitHub's official releases page. Ensure all CI/CD pipelines and policy gates are updated to use the patched version.

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