# CVE-2026-44309: gitsign verify accepts signatures over go-git-normalized bytes, enabling trust confusion on malformed commits

> Attackers can craft malformed commits that pass gitsign verification but resolve to different content in git-core, bypassing signature integrity checks.

- **Severity:** Medium 5.3 (`CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:N/I:H/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** A user has to click or open something
- **Fix available:** Yes
- **Published:** 15 May 2026
- **Updated:** 15 May 2026
- **Also known as:** DEBIAN-CVE-2026-44309, GHSA-7rmh-48mx-2vwc, GO-2026-5233, UBUNTU-CVE-2026-44309

## What is CVE-2026-44309?

CVE-2026-44309 is a medium-severity vulnerability in sigstore gitsign, published on 15 May 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.

### Official 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.

Weakness: CWE-347 (Improper Verification of Cryptographic Signature), CWE-295 (Improper Certificate Validation)

## Which versions are affected by CVE-2026-44309?

3 open source packages ship an affected version, including github.com/sigstore/gitsign.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `github.com/sigstore/gitsign` | Go | All versions | 0.16.0 |
| `github.com/sigstore/gitsign` | Go | All versions | 0.16.0 |
| `github.com/sigstore/gitsign` | Go | All versions | 0.16.0 |

## How do I fix CVE-2026-44309?

Upgrade github.com/sigstore/gitsign to 0.16.0 or later.

## Is CVE-2026-44309 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-44309 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-44309 and fix it if it is affected.

What it is: CVE-2026-44309 is a medium-severity vulnerability in sigstore gitsign, published on 15 May 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-44309 exists.

Affected packages and fixed versions:
- github.com/sigstore/gitsign (Go): affected all versions; fixed in 0.16.0
- github.com/sigstore/gitsign (Go): affected all versions; fixed in 0.16.0
- github.com/sigstore/gitsign (Go): affected all versions; fixed in 0.16.0

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-44309/ (Markdown: https://insights.sbomify.com/CVE-2026-44309/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-44309
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-44309
- OSV: https://osv.dev/vulnerability/CVE-2026-44309

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-44309/
Summaries are generated and may contain mistakes; the official description above is the record.