# CVE-2026-53507: Server-side request forgery in oasdiff-action

> Attackers can trigger SSRF and read sensitive files on CI runners via malicious OpenAPI specs in pull requests using oasdiff-action.

- **Severity:** High 8.3 (`CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:L/VA:N/SC:N/SI:N/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 31 Aug 2026
- **Updated:** 1 Sep 2026
- **Also known as:** GHSA-fhj3-7267-7vv5

## What is CVE-2026-53507?

CVE-2026-53507 is a high-severity server-side request forgery vulnerability in oasdiff-action, published on 31 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

oasdiff-action is a GitHub Action that detects breaking changes in OpenAPI specs and post a review on every pull request. Before version 0.0.51, the oasdiff actions resolved external $refs in the OpenAPI spec by default (allow-external-refs: true). When an action runs on a pull request whose spec is attacker-controlled — most importantly fork pull requests on public repositories — a $ref in that spec is fetched/read on the runner with no interaction required, enabling SSRF and disclosure of structured files on the runner. This issue has been patched in version 0.0.51.

Weakness: CWE-918 (Server-Side Request Forgery), CWE-200 (Exposure of Sensitive Information to an Unauthorized Actor), CWE-1188 (Initialization of a Resource with an Insecure Default)

## Which versions are affected by CVE-2026-53507?


## How do I fix CVE-2026-53507?

No fix has been published for CVE-2026-53507 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-53507 being exploited?

There is no known exploitation of CVE-2026-53507 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-53507 and fix it if it is affected.

What it is: CVE-2026-53507 is a high-severity server-side request forgery vulnerability in oasdiff-action, published on 31 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-53507 in the wild and no public exploit code.

Affected product: oasdiff-action. No package-level version data is available, so check the vendor advisory linked from the reference page.

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-2026-53507/ (Markdown: https://insights.sbomify.com/CVE-2026-53507/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-53507
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-53507
- OSV: https://osv.dev/vulnerability/CVE-2026-53507

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-53507/
Summaries are generated and may contain mistakes; the official description above is the record.