CVE-2026-44309
MEDIUMCVE-2026-44309 is a medium-severity (CVSS 5.3) vulnerability in github.com/sigstore/gitsign. O3 Security confirms whether CVE-2026-44309 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
gitsign verify accepts signatures over go-git-normalized bytes, enabling trust confusion on malformed commits
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
Blast Radius
github.com/sigstore/gitsignReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects Go packages — download data is not available via public APIs for these ecosystems.
Description
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.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐹Go | github.com/sigstore/gitsign | all versions | 0.16.0 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/sigstore/gitsign. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update github.com/sigstore/gitsign to 0.16.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-44309 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether CVE-2026-44309 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to CVE-2026-44309. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2026-44309 in your dependencies?
O3 detects CVE-2026-44309 across Go dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.