kin-openapi: YAML NaN/Inf Values Bypass Built-in Guards and Panic via OAS 3.1 Validation Path

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

7.5 · CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

EPSS

• CVE-2026-100352: 0.60% estimated exploitation activity in the next 30 days; percentile 48.48 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Summary kin-openapi guards against NaN and Inf values in its built-in schema visitor (visitJSON) by returning ErrSchemaInputNaN / ErrSchemaInputInf when a float64 input violates those constraints. For OAS 3.1 specs, however, Schema.VisitJSON routes through useJSONSchema2020, which hands the value directly to santhosh-tekuri/jsonschema/v6 v6.0.2 without applying the same guard. Inside jsonschema/v6 v6.0.2, numValidate builds a big.Rat from the input via big.Rat.SetString(fmt.Sprintf("%v", v)). For NaN/Inf this parse fails silently and returns nil. numValidate then dereferences the nil big.Rat (in math/big.(Rat).Cmp), producing a Go runtime panic. An attacker delivers this by sending an HTTP request with Content-Type: application/yaml (or application/x-yaml) and a YAML body containing .nan, .inf, or -.inf. The YamlBodyDecoder decodes those tokens into math.NaN() / math.Inf(±1) (standard YAML 1.2 behavior), and they propagate to the unguarded useJSONSchema2020 path whenever the schema…

Published by the source

15 Oct 2026, 20:20 UTC

Last modified by the source

15 Oct 2026, 20:30 UTC

Source last checked

26 Oct 2026, 15:32 UTC

1. Revision 2 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-rj39-cv6w-8wv7

2. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-rj39-cv6w-8wv7

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# Patch Next advisory brief: CVE-2026-100352

Advisory: kin-openapi: YAML NaN/Inf Values Bypass Built-in Guards and Panic via OAS 3.1 Validation Path
IDs: CVE-2026-100352, GHSA-rj39-cv6w-8wv7
Record: https://patchnext.com/advisories/cve-2026-100352 (revision 2, source checked 26 Oct 2026, 15:32 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 7.5)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: github.com/getkin/kin-openapi 0.148.0. A vendor fix does not mean a deployment is fixed.

## Affected components
- Go github.com/getkin/kin-openapi: affected < 0.148.0; fixed in 0.148.0

## Suggested inspection (read-only)
- Go github.com/getkin/kin-openapi: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on github.com/getkin/kin-openapi.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/GHSA-rj39-cv6w-8wv7 (OSV record GHSA-rj39-cv6w-8wv7 lists affected ranges: Go github.com/getkin/kin-openapi >=0 <0.148.0 (fixed))
- Verified: https://github.com/advisories/GHSA-rj39-cv6w-8wv7 (GitHub-reviewed advisory GHSA-rj39-cv6w-8wv7 lists affected ranges: Go github.com/getkin/kin-openapi >=0 <0.148.0)

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