How severe is CVE-2026-53508?

No CVSS score has been assigned to CVE-2026-53508 yet. Review the advisory details and affected package list to assess your exposure.

Which packages are affected by CVE-2026-53508?

CVE-2026-53508 affects the following packages: github.com/oasdiff/oasdiff (Go). Ecosystems affected: Go.

How do I fix CVE-2026-53508?

Update github.com/oasdiff/oasdiff to 1.18.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-53508 is resolved across your whole dependency graph.

How do I detect CVE-2026-53508 in my Go dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/oasdiff/oasdiff, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

How do I mitigate CVE-2026-53508 if there is no patch (or I can't update yet)?

Restrict outbound requests from the affected component to an allowlist of hosts, block access to link-local and internal address ranges at the network layer, and require authentication on internal services so a forged request cannot reach them unauthenticated.

Is CVE-2026-53508 actively exploited in the wild?

No public exploit code has been indexed for CVE-2026-53508 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for CVE-2026-53508?

CVE-2026-53508 has an EPSS (Exploit Prediction Scoring System) score of 0.5%, placing it in the 42th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is CVE-2026-53508?

CVE-2026-53508 is classified as CWE-73 (CWE-73), CWE-693 (CWE-693), Server-Side Request Forgery (SSRF) (CWE-918). These weakness types describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation. This is a high-impact weakness class that often enables remote code execution or data exposure.

When was CVE-2026-53508 published, and has it been updated?

CVE-2026-53508 was published on August 31, 2026 and was last updated on October 21, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

🐹 Go

Not in CISA KEV

CVE-2026-53508 — oasdiff

Fix: oasdiff/oasdiff#832

CVE-2026-53508 is a CWE-73 vulnerability in github.com/oasdiff/oasdiff. A fix is available for github.com/oasdiff/oasdiff — see the affected versions and patch details below.

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

Also known asGHSA-2jcc-mxv7-p3f9GO-2026-5937

Published

Aug 31, 2026

Updated

Oct 21, 2026

Affected

1 pkg

Patched

1 / 1

Exploits

None indexed

Exploitation data as of Oct 21, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

EPSS Exploitation Probability

via FIRST.org ↗

0.5%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs42th percentile — riskier than 42% of all scored CVEsHighest risk

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

Real-World Exposure

1 pkg affected

🐹github.com/oasdiff/oasdiff

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects Go packages — download data is not available via public APIs for these ecosystems.

Description

Summary

From 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 $refs were resolved on that load path even when external refs were explicitly disabled, so the mitigation silently did not apply there.

Impact

A caller who set --allow-external-refs=false specifically to safely process untrusted specs remained exposed — on the git-revision load path only — to:

SSRF via $ref: "http://<internal-host>/…", and
Local file reads via $ref: "/path" or file://.

Affected callers:

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.
Go library consumers of github.com/oasdiff/oasdiff/load that set IsExternalRefsAllowed = false and load from a git-revision source via load.NewSpecInfo.

The 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.

Patches

v1.18.1 enforces the external-refs policy on the git-revision path (so --allow-external-refs=false now blocks external $refs there) and returns a dedicated exit code (123) when an external $ref is refused.

Workarounds

Upgrade to v1.18.1, or
Avoid the git-revision input form when processing untrusted specs with external refs disabled.

Notes

Introduced in v1.13.2 (#832, which added $ref-chain resolution on the git-revision path); fixed in v1.18.1 (#974, #975).
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).

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
🐹Go	`github.com/oasdiff/oasdiff`	≥ 1.13.2&&< 1.18.1	1.18.1`go get github.com/oasdiff/oasdiff@v1.18.1`

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/oasdiff/oasdiff, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update github.com/oasdiff/oasdiff to 1.18.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-53508 is resolved across your whole dependency graph.
Workarounds
Restrict outbound requests from the affected component to an allowlist of hosts, block access to link-local and internal address ranges at the network layer, and require authentication on internal services so a forged request cannot reach them unauthenticated.

Frequently Asked Questions

## Summary From **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 `$ref`s were resolved on that load path even when external refs were explicitly disabled, so the mitigation silently did not apply there. ## Impact A caller who set `--allow-external-refs=false` *specifically to safely process untrusted specs* remained exposed — on the git-revision load path only — to: - **SSRF** via `$ref: "http:

O3 Security · Impact-Aware SCA

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