What’s Vulnerable › Vulnerabilities

CVE-2026-53507: oasdiff actions resolve external $refs by default, enabling SSRF and disclosure of structured files on pull-request runs

• Severity: high (CVSS 8.3 v4.0)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.5% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-08-31 · updated 2026-09-09
• Weakness: CWE-200

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-action: before 0.0.51

References

• https://github.com/oasdiff/oasdiff-action/pull/128
• https://github.com/oasdiff/oasdiff-action/pull/129
• https://github.com/oasdiff/oasdiff-action/pull/130
• https://github.com/oasdiff/oasdiff-action/security/advisories/GHSA-fhj3-7267-7vv5

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