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CVE-2026-5430

The JWT authentication mechanism accepts tokens signed with algorithms other than those explicitly configured or supported.

Critical Known exploited
Severity
10.0 / 10
Critical · CVSS 3.1
Exploit chance (EPSS)
22.39%
Chance of exploitation in the next 30 days. Higher than 97.69% of scored vulnerabilities.
Known exploited
Yes
In CISA's catalog since Sep 24, 2026
Weakness
CWE-347 Improper Verification of Cryptographic Signature
Fix
None yet
No fixed version published
Exploited in the wild. WSO2 Multiple Products Path Traversal Vulnerability (WSO2 Multiple Products). Required action: Apply mitigations in accordance with vendor instructions, ensuring compliance with CISA’s BOD 26-04 Prioritizing Security Updates Based on Risk (see URL in Notes) guidance and CISA’s “Forensics Triage Requirements” (see URL in Notes). Follow applicable BOD 26-04 guidance for cloud services or discontinue use of the product if mitigations are unavailable. Stakeholders are responsible for evaluating each asset's internet exposure and ensuring adherence to BOD 26-04 patching guidelines. Due for U.S. federal agencies by Sep 27, 2026.

Description

The JWT authentication mechanism accepts tokens signed with algorithms other than those explicitly configured or supported. This allows an attacker to craft a JWT with an unsupported algorithm, which is then incorrectly validated, leading to unauthorized access.

Successful exploitation of this vulnerability may result in unauthorized access to the system, including the potential compromise of administrative accounts and full account takeover. The CVSS score is adjusted to 9.8 (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H) in single-tenant deployments, reflecting that the impact is contained within a single security authority boundary.

How to fix

No fixed version has been published yet. Until one is, remove or replace the package, or turn off or isolate the affected feature. This page updates when a fix ships.

Severity breakdown

CVSS 3.1 10.0

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

Attack vector
Network
Attack complexity
Low
Privileges required
None
User interaction
None
Scope
Changed
Confidentiality
High
Integrity
High
Availability
High

Weakness

CWE-347: Improper Verification of Cryptographic Signature

The product does not verify, or incorrectly verifies, the cryptographic signature for data.

References

Advisories

Other links

Timeline

  1. Published
  2. Added to CISA's Known Exploited Vulnerabilities catalog
  3. Last updated by the source
  4. Remediation due for U.S. federal agencies
  5. Latest EPSS score
AdvisorySeverityWhy it's related
EEF-CVE-2026-65632
ECDSA signature length is not validated in jose, allowing signature malleability
Not rated yet Same weakness, CWE-347
GHSA-pxh4-856f-4h89
PyJWT: HS256/384/512 verify accepts empty HMAC key via oct JWK (PyJWK/PyJWKClient) enabling token forgery
High Same weakness, CWE-347
GHSA-j7h2-66j4-ghjf
A russh SSH server accepts a publickey authentication whose signature uses a different algorithm than the one named in the request
Low Same weakness, CWE-347
GHSA-w2cx-738m-mc7w
PyJWT accepts public JWK containers as HMAC secrets
High Same weakness, CWE-347
GHSA-r6x4-923q-g947
PyJWT BOM Bypass
High Same weakness, CWE-347
GHSA-p4g4-x82p-q773
PyJWT: Public keys in DER form are accepted as HMAC secrets, bypassing the CVE-2022-29217 guard
High Same weakness, CWE-347
GHSA-ffc3-869f-jxw9
PyJWT: Asymmetric-PEM detection bypass: whitespace/line-ending-mutated public keys skip the HS/asymmetric confusion guard
Critical Same weakness, CWE-347
GHSA-9j54-fg26-wv3r
PyJWT: PyJWK accepts empty HMAC keys, bypassing PyJWT's empty-key validation
Critical Same weakness, CWE-347
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