# CVE-2026-53507

## Summary

- **CVE ID:** CVE-2026-53507
- **Severity:** HIGH
- **CVSS Score:** 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)
- **CWE:** CWE-200, CWE-918, CWE-1188
- **Published:** Aug 31, 2026
- **Last Modified:** Sep 1, 2026

## 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.

## Affected Products

- oasdiff — oasdiff-action (< 0.0.51)

## References

- [CNA](https://github.com/oasdiff/oasdiff-action/security/advisories/GHSA-fhj3-7267-7vv5)
- [CNA](https://github.com/oasdiff/oasdiff-action/pull/128)
- [CNA](https://github.com/oasdiff/oasdiff-action/pull/129)
- [CNA](https://github.com/oasdiff/oasdiff-action/pull/130)

## Exploitation Prediction (EPSS)

- **EPSS Score:** 0.29%
- **EPSS Percentile:** 20.9

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_Exported from OnDuty AI Vulnerability Intelligence on 2026-09-11._