jsonwebtoken has Type Confusion that leads to potential authorization bypass

Exploitation

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

CVSS 4.0

5.5 · CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N/E:P · score source

EPSS

• CVE-2026-25537: 0.50% estimated exploitation activity in the next 30 days; percentile 42.62 (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: It has been discovered that there is a Type Confusion vulnerability in jsonwebtoken, specifically, in its claim validation logic. When a standard claim (such as nbf or exp) is provided with an incorrect JSON type (Like a String instead of a Number), the library’s internal parsing mechanism marks the claim as “FailedToParse”. Crucially, the validation logic treats this “FailedToParse” state identically to “NotPresent”. This means that if a check is enabled (like: validatenbf = true), but the claim is not explicitly marked as required in requiredspecclaims, the library will skip the validation check entirely for the malformed claim, treating it as if it were not there. This allows attackers to bypass critical time-based security restrictions (like “Not Before” checks) and commit potential authentication and authorization bypasses. Details: The vulnerability stems from the interaction between the TryParse enum and the validate function in src/validation.rs. 1. The TryParse…

Published by the source

3 Feb 2026, 18:47 UTC

Last modified by the source

5 Feb 2026, 00:35 UTC

Source last checked

26 Oct 2026, 15:39 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-h395-gr6q-cpjc

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# Patch Next advisory brief: CVE-2026-25537

Advisory: jsonwebtoken has Type Confusion that leads to potential authorization bypass
IDs: CVE-2026-25537, GHSA-h395-gr6q-cpjc
Record: https://patchnext.com/advisories/cve-2026-25537 (revision 1, source checked 26 Oct 2026, 15:39 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 5.5)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: jsonwebtoken 10.3.0. A vendor fix does not mean a deployment is fixed.

## Affected components
- crates.io jsonwebtoken: affected < 10.3.0; fixed in 10.3.0

## Suggested inspection (read-only)
- crates.io jsonwebtoken: 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 jsonwebtoken.
- 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://github.com/advisories/GHSA-h395-gr6q-cpjc (GitHub-reviewed advisory GHSA-h395-gr6q-cpjc lists affected ranges: crates.io jsonwebtoken >=0 <10.3.0)

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