oasdiff up to 1.18.0 Loader openapi3.Loader.IsExternalRefsAllowed allow-external-refs server-side request forgery

Summaryinfo

A vulnerability identified as critical has been detected in oasdiff up to 1.18.0. Impacted is the function openapi3.Loader.IsExternalRefsAllowed of the component Loader. Performing a manipulation of the argument allow-external-refs results in server-side request forgery. This vulnerability was named CVE-2026-53508. The attack may be initiated remotely. There is no available exploit.

Detailsinfo

A vulnerability classified as critical has been found in oasdiff up to 1.18.0. This affects the function openapi3.Loader.IsExternalRefsAllowed of the component Loader. The manipulation of the argument allow-external-refs with an unknown input leads to a server-side request forgery vulnerability. CWE is classifying the issue as CWE-918. The web server receives a URL or similar request from an upstream component and retrieves the contents of this URL, but it does not sufficiently ensure that the request is being sent to the expected destination. This is going to have an impact on confidentiality, integrity, and availability. The summary by CVE is:

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.

The advisory is shared at github.com. This vulnerability is uniquely identified as CVE-2026-53508 since 06/09/2026. The exploitability is told to be easy. It is possible to initiate the attack remotely. No form of authentication is needed for exploitation. It demands that the victim is doing some kind of user interaction. Technical details are known, but no exploit is available.

Upgrading to version 1.18.1 eliminates this vulnerability.

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Productinfo

Name

• oasdiff

Version

• 1.0
• 1.1
• 1.2
• 1.3
• 1.4
• 1.5
• 1.6
• 1.7
• 1.8
• 1.9
• 1.10
• 1.11
• 1.12
• 1.13
• 1.14
• 1.15
• 1.16
• 1.17
• 1.18.0

Website

• Product: https://github.com/oasdiff/oasdiff/

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