Trust bypass via normalized-object signature verification
Published May 15, 2026 · Updated May 15, 2026
Improper signature verification in Sigstore Gitsign before 0.16.0 allows remote attackers to pass malicious Git content as trusted. The verify and verify-tag paths call go-git's EncodeWithoutSignature and validate reconstructed bytes, so duplicate tree headers make the signed tree differ from the tree git-core uses. Exploitation requires a victim to verify a specially malformed commit or tag that survives repository checks; signature replay can endorse attacker-controlled content without the signing key.
Summary
What happened
Improper signature verification in Sigstore Gitsign before 0.16.0 allows remote attackers to pass malicious Git content as trusted. The verify and verify-tag paths call go-git's EncodeWithoutSignature and validate reconstructed bytes, so duplicate tree headers make the signed tree differ from the tree git-core uses. Exploitation requires a victim to verify a specially malformed commit or tag that survives repository checks; signature replay can endorse attacker-controlled content without the signing key.
The record
- CVE
- CVE-2026-44309
- Published
- May 15, 2026
- Updated
- May 15, 2026
- Vendor
- Sigstore
- Product
- Gitsign
- Classifications
- CWE-347, CWE-295, T1553.002
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- May 15, 2026CVE publishedPublication date reported by the CVE source.
- May 15, 2026Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
Compare these published version ranges with your installed build and any vendor patches.
- Affected versionversion=< 0.16.0
What conditions does exploitation require?
What is affected?
Published CVSS scores
CVSS describes severity. EPSS estimates exploitation probability.
Attacks
What attackers are doing with it
Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.
Weakness, pattern, technique
Public exploit references
- Duplicate-tree signature replay proof of conceptproof of concept · demonstrated
Labels summarize the accepted research assessment. They do not indicate a test against your environment.
Technologies
Your stack
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Your stack
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