Which versions of Jwt Attack are affected by CVE-2026-5466?

wolfSSL's ECCSI signature verification contains a bypass allowing unauthenticated attackers on adjacent networks to forge cryptographic signatures for any message and identity, compromising the…. A patch is available.

How to fix or mitigate CVE-2026-5466?

Within 24 hours: Identify all systems using wolfSSL ECCSI implementation and document current library versions. Within 7 days: Apply vendor-released patch to wolfSSL and conduct code review of signature verification call sites, particularly JWT authentication handlers. Within 30 days: Perform cryptographic audit of all ECCSI-signed credentials issued while running vulnerable versions and implement certificate/token revocation as needed.

Jwt Attack CVE-2026-5466

Q: What is the CVSS score of CVE-2026-5466?

CVE-2026-5466 has a CVSS 4.0 base score of 7.6 (High). CVSS vector: CVSS:4.0/AV:A/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X. EPSS exploitation probability: 0.0%.

EUVD-2026-21291 HIGH

Improper Verification of Cryptographic Signature (CWE-347)

2026-04-10 wolfSSL

GHSA-47qf-hp3h-rwmm

Information Disclosure Jwt Attack

7.6

CVSS 4.0 · NVD

Severity by source

NVD PRIMARY

7.6 HIGH

CVSS:4.0/AV:A/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

Primary rating from NVD · only source for this CVE.

CVSS VectorNVD

CVSS:4.0/AV:A/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

Attack Vector

Adjacent

Attack Complexity

Low

Privileges Required

None

User Interaction

None

Scope

Lifecycle Timeline

Re-analysis Queued

Apr 29, 2026 - 13:52 vuln.today

cvss_changed

Analysis Updated

Apr 16, 2026 - 05:59 EUVD-patch-fix

executive_summary

Re-analysis Queued

Apr 16, 2026 - 05:29 backfill_euvd_patch

patch_released

Patch available

Apr 16, 2026 - 05:29 EUVD

5.9.1

EUVD ID Assigned

Apr 10, 2026 - 03:45 euvd

EUVD-2026-21291

Analysis Generated

Apr 10, 2026 - 03:45 vuln.today

CVE Published

Apr 10, 2026 - 03:00 nvd

HIGH 7.6

DescriptionCVE.org

wolfSSL's ECCSI signature verifier wc_VerifyEccsiHash decodes the r and s scalars from the signature blob via mp_read_unsigned_bin with no check that they lie in [1, q-1]. A crafted forged signature could verify against any message for any identity, using only publicly-known constants.

AnalysisAI

Signature verification bypass in wolfSSL's ECCSI implementation allows adjacent network attackers to forge cryptographic signatures for any message and identity without authentication. The wc_VerifyEccsiHash function fails to validate that signature scalars r and s fall within the required mathematical range [1, q-1], enabling attackers with knowledge of public constants to craft universally-valid forged signatures. This defeats the cryptographic integrity guarantees of ECCSI-signed data, particularly affecting JWT authentication systems and identity-based cryptographic protocols. No public exploit identified at time of analysis.

Technical ContextAI

Root cause is missing input validation in mp_read_unsigned_bin calls when decoding signature scalars. CWE-347 (improper signature verification) stems from absent modular arithmetic boundary checks against elliptic curve order q. Attackers exploit this by constructing signature blobs with out-of-range scalar values that satisfy verification equations using only public domain parameters, bypassing the discrete logarithm problem that normally secures ECDSA-family schemes.

RemediationAI

Vendor-released patch: wolfSSL 5.9.1. Immediately upgrade to version 5.9.1 or later, which implements mandatory range validation for ECCSI signature scalars. Upstream fix available at https://github.com/wolfssl/wolfssl/pull/10102. Organizations unable to upgrade immediately must disable ECCSI signature verification functionality in wolfSSL configurations and migrate ECCSI-dependent authentication flows (particularly JWT with ECCSI algorithms) to alternative cryptographic schemes such as ECDSA or RSA-PSS until patching is completed. Verify that no production systems accept ECCSI-signed tokens or messages during the interim period. Review application logs for anomalous authentication patterns that may indicate exploitation attempts prior to remediation.