{"id":"CVE-2026-53508","aliases":["GHSA-2jcc-mxv7-p3f9","GO-2026-5937"],"url":"https://o3.security/vulnerability/CVE-2026-53508","summary":"oasdiff does not enforce --allow-external-refs=false on the git-revision load path (SSRF / local file read)","details":"## Summary\n\nFrom **v1.13.2** through **v1.18.0**, 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 `$ref`s were resolved on that load path even when external refs were explicitly disabled, so the mitigation silently did not apply there.\n\n## Impact\n\nA caller who set `--allow-external-refs=false` *specifically to safely process untrusted specs* remained exposed — on the git-revision load path only — to:\n\n- **SSRF** via `$ref: \"http://<internal-host>/…\"`, and\n- **Local file reads** via `$ref: \"/path\"` or `file://`.\n\nAffected callers:\n\n- **CLI:** `oasdiff diff main:openapi.yaml HEAD:openapi.yaml --allow-external-refs=false` (and `breaking` / `changelog` / `summary`, and the `git-diff-driver`) run over untrusted spec content.\n- **Go library consumers** of `github.com/oasdiff/oasdiff/load` that set `IsExternalRefsAllowed = false` and load from a git-revision source via `load.NewSpecInfo`.\n\nThe file and URL load paths correctly enforced the setting; only the git-revision path was affected. Callers that left external refs at the default (`true`) are not in scope for *this* advisory.\n\n## Patches\n\n**v1.18.1** enforces the external-refs policy on the git-revision path (so `--allow-external-refs=false` now blocks external `$ref`s there) and returns a dedicated exit code (`123`) when an external `$ref` is refused.\n\n## Workarounds\n\n- Upgrade to **v1.18.1**, or\n- Avoid the git-revision input form when processing untrusted specs with external refs disabled.\n\n## Notes\n\n- Introduced in **v1.13.2** (#832, which added `$ref`-chain resolution on the git-revision path); fixed in **v1.18.1** (#974, #975).\n- The permissive **default** (`allow-external-refs: true`) and its zero-interaction exposure in CI via the GitHub Action is tracked separately in GHSA-fhj3-7267-7vv5 (oasdiff-action).","published":"2026-08-31T18:52:12.213Z","modified":"2026-10-21T02:58:29.480265469Z","cvss":null,"epss":{"score":0.00288,"percentile":0.21453,"asOf":"2026-09-17"},"cisaKev":null,"exploitsKnown":0,"affectedPackages":[{"ecosystem":"Go","name":"github.com/oasdiff/oasdiff","fixedVersion":"1.18.1"}],"fix":{"url":"https://github.com/oasdiff/oasdiff/pull/832","label":"oasdiff/oasdiff#832"},"references":[{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/53xxx/CVE-2026-53508.json"},{"type":"ADVISORY","url":"https://github.com/oasdiff/oasdiff/security/advisories/GHSA-2jcc-mxv7-p3f9"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-53508"},{"type":"FIX","url":"https://github.com/oasdiff/oasdiff/pull/832"},{"type":"FIX","url":"https://github.com/oasdiff/oasdiff/pull/974"},{"type":"FIX","url":"https://github.com/oasdiff/oasdiff/pull/975"},{"type":"PACKAGE","url":"https://github.com/oasdiff/oasdiff"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-10-21T02:58:29.480265469Z"}}