CVE-2026-64655
GitHub CLI allows attestation verification bypass through unescaped regex metacharacters
Published Oct 15, 2026 · corrected/updated Oct 15, 2026 · evidence confidence high
### Summary A security vulnerability has been identified in GitHub CLI that could allow attestation verification bypass when using with or flags. GitHub CLI builds the certificate matcher from these flag values without escaping regex metacharacters, so a repository or workflow name is treated as a regular expression rather than a literal string. GitHub permits characters such as in organization, repository, and workflow path names, and is a regex wildcard, so a malicious actor can create a lookalike name that satisfies a matcher intended for a different, trusted signer. ### Details GitHub CLI constructs a regular expression from the and values and matches it against the signing certificate's SAN (Subject Alternative Name) during Sigstore attestation verification. The user-supplied value is interpolated into the pattern without escaping regex metacharacters, so any metacharacter permitted in a GitHub path is interpreted as regex syntax instead of a literal character. The most practical case is , which GitHub allows in org/repo names and is a regex wildcard meaning "any single character." For example, an attacker-controlled repository named: matches a verifier configured for the trusted signer: because the unescaped in the constructed pattern matches the in the attacker's name (and any other single character at that position). This affected the and flags but did not affect the and flags which include an exact string comparison. In , the GitHub CLI escapes the user-supplied signer values before they are incorporated into the SAN matcher, so they are matched as literal strings. ### Impact The practical impact is limited, exploitation requires the attacker to create a plausible lookalike repository name and produce valid Sigstore attestations from it. This could undermine supply chain verification for CI/CD pipelines or policy gates that use these flags to pin trust to a specific signing workflow. ### Remediation and Mitigation 1. Upgrade to or later, which escapes signe
Grounded briefings
Catalog interpretations for three audiences. Each brief cites ingested metadata and the original advisories below. They are not independent research and they do not invent exploit steps.
Executive
CVE-2026-64655 is a low public vulnerability record for this product. It is not currently listed in the CISA Known Exploited catalog. Check the linked vendor or CERT advisories for patch status. This summary is a catalog interpretation of the ingested metadata and cites the original advisories below.
System administrator
Identify whether this product is in your estate, then compare installed versions with the affected ranges. Affected packages or ranges on record: github.com/cli/cli/v2 (0 → 2.97.0); github.com/cli/cli/v2 (< 2.97.0); github.com. Check the linked vendor or CERT advisories for patch status. Prefer the vendor or distribution advisory linked in Sources before changing production systems. This is a catalog interpretation, not a runbook.
Security analyst
Signals on file: no CVSS/EPSS yet. It is not currently listed in the CISA Known Exploited catalog. Weakness classes: CWE-185. Sources contributing to this record: cve_org, github, gitlab, osv. Public exploit references, when present, are outbound links only and are not proof of active exploitation. This is a catalog interpretation of stored metadata.
Exploitation and remediation
Exploitation evidence
Not listed as known exploited in CISA KEV. Not in CISA KEV or VulnCheck KEV.
Patch and remediation
No required-action text is stored yet. Use the vendor or CERT links in Sources for patch availability.
Safe detection guidance
Compare installed versions with the affected ranges below and verify the advisory from the original publisher. This site stores metadata and outbound links only; it does not ship exploit code or proof-of-concept payloads.
Code
The project this record applies to. Exploit listings stay in References.
Timeline
Detection, updates, and resolution for this record.
Oct 15, 2026 · GitHub Advisory Database
Detected
### Summary A security vulnerability has been identified in GitHub CLI that could allow attestation verification bypass when using with or flags. GitHub CLI builds the certificate matcher from these flag values without escaping regex metacharacters, so a repository or workflow name is treated as a regular expression rather than a literal string. GitHub permits characters such as in organization, r
Oct 15, 2026 · GitHub Advisory Database
Fix available
github.com/cli/cli/v2 fixed in 2.97.0
Oct 15, 2026 · GitHub Advisory Database
Fix available
github.com/cli/cli/v2 fixed in 2.97.0
Oct 15, 2026 · GitHub Advisory Database
Updated
### Summary A security vulnerability has been identified in GitHub CLI that could allow attestation verification bypass when using with or flags. GitHub CLI builds the certificate matcher from these flag values without escaping regex metacharacters, so a repository or workflow name is treated as a regular expression rather than a literal string. GitHub permits characters such as in organization, r
Affected
- Go github.com/cli/cli/v20 → 2.97.0
- go github.com/cli/cli/v2< 2.97.0
- golang github.comversion unspecified
Sources
- CVE.orgVulnerability recordCVE-2026-64655
Official CVE identifier
cve.org - GitHub Advisory DatabasePackage advisoryGHSA-mm27-mwq9-fr5g
GitHub Advisory Database record mirrored by OSV.
github.com - GitLab Advisory DatabasePackage advisoryCVE-2026-64655
A security vulnerability has been identified in GitHub CLI that could allow attestation verification bypass when using gh attestation verify with –signer-repo or –signer-workflow flags. GitHub CLI builds the certificate matcher from these flag values without escaping regex metacharacters, so a repository or workflow name is treated as a regular expression rather than a literal string.
advisories.gitlab.com - OpenSSF OSV / OSV ScannerPackage advisoryGHSA-mm27-mwq9-fr5g
GitHub CLI allows attestation verification bypass through unescaped regex metacharacters
osv.dev