Bug 2477933 (CVE-2026-44309)

Summary: CVE-2026-44309 github.com/sigstore/gitsign: github.com/go-git/go-git: Gitsign: Signature verification bypass due to object re-encoding
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
Status: NEW --- QA Contact:
Severity: medium Docs Contact:
Priority: medium    
Version: unspecifiedCC: eborisov, lball, ngough, veshanka
Target Milestone: ---Keywords: Security
Target Release: ---   
Hardware: All   
OS: Linux   
Whiteboard:
Fixed In Version: Doc Type: ---
Doc Text:
A flaw was found in gitsign, a tool used for signing Git commits. This vulnerability, affecting the `verify` and `verify-tag` functions, occurs because gitsign re-encodes commit and tag objects before validating their signatures. A remote attacker could exploit this by crafting a malformed git object, causing gitsign to accept a signature that, when processed by git-core, refers to a different and potentially malicious commit. This effectively bypasses signature verification, compromising the integrity of signed Git commits.
 Story Points: ---
Clone Of: Environment:
Last Closed: Type: ---
Regression: --- Mount Type: ---
Documentation: --- CRM:
Verified Versions: Category: ---
oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: --- Target Upstream Version:
Embargoed:
Bug Depends On: 2489139    
Bug Blocks:    

Description OSIDB Bzimport 2026-05-15 17:01:22 UTC 
Gitsign is a keyless Sigstore to signing tool for Git commits with your a GitHub / OIDC identity. Prior to 0.16.0, gitsign verify and gitsign verify-tag re-encode commit/tag objects through go-git's EncodeWithoutSignature before checking the signature, instead of verifying against the raw git object bytes. For malformed objects with duplicate tree headers, git-core and go-git parse different trees: git-core uses the first, go-git uses the second. A signature crafted over the go-git-normalized form (second tree) passes gitsign verify while git-core resolves the commit to a completely different tree. This breaks the invariant that a verified signature, the commit semantics git-core presents to users, and the object hash logged in Rekor all refer to the same content. This vulnerability is fixed in 0.16.0.