CVE-2026-35041: CWE-1333: Inefficient Regular Expression Complexity in nearform fast-jwt
CVE-2026-35041 is a medium severity vulnerability in nearform's fast-jwt library versions 5. 0. 0 through 6. 2. 0. It involves inefficient regular expression complexity when the allowedAud verification option is configured with a regular expression. An attacker-controlled 'aud' claim in a JWT can trigger catastrophic backtracking in the JavaScript regex engine, causing significant CPU consumption and a denial-of-service condition during token verification. This issue is fixed in version 6. 2. 1.
AI Analysis
Technical Summary
The fast-jwt library, used for JSON Web Token implementation, contains a denial-of-service vulnerability in versions from 5.0.0 up to but not including 6.2.1. When the allowedAud verification option is set using a regular expression, the library evaluates the attacker-controlled 'aud' claim against this regex. Crafted JWTs can exploit inefficient regex evaluation leading to catastrophic backtracking and excessive CPU usage. This vulnerability is tracked as CWE-1333 and has a CVSS 3.1 base score of 4.2 (medium severity). The issue is resolved in fast-jwt version 6.2.1.
Potential Impact
Successful exploitation results in a denial-of-service condition due to high CPU consumption during JWT verification. There is no impact on confidentiality or integrity, only availability is affected. The vulnerability requires high attack complexity and privileges with user interaction, limiting its exploitability.
Mitigation Recommendations
Upgrade fast-jwt to version 6.2.1 or later where this vulnerability is fixed. Since the vendor advisory indicates the issue is resolved in 6.2.1, applying this official fix is the recommended remediation. No alternative mitigations or workarounds are provided.
CVE-2026-35041: CWE-1333: Inefficient Regular Expression Complexity in nearform fast-jwt
Description
CVE-2026-35041 is a medium severity vulnerability in nearform's fast-jwt library versions 5. 0. 0 through 6. 2. 0. It involves inefficient regular expression complexity when the allowedAud verification option is configured with a regular expression. An attacker-controlled 'aud' claim in a JWT can trigger catastrophic backtracking in the JavaScript regex engine, causing significant CPU consumption and a denial-of-service condition during token verification. This issue is fixed in version 6. 2. 1.
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
The fast-jwt library, used for JSON Web Token implementation, contains a denial-of-service vulnerability in versions from 5.0.0 up to but not including 6.2.1. When the allowedAud verification option is set using a regular expression, the library evaluates the attacker-controlled 'aud' claim against this regex. Crafted JWTs can exploit inefficient regex evaluation leading to catastrophic backtracking and excessive CPU usage. This vulnerability is tracked as CWE-1333 and has a CVSS 3.1 base score of 4.2 (medium severity). The issue is resolved in fast-jwt version 6.2.1.
Potential Impact
Successful exploitation results in a denial-of-service condition due to high CPU consumption during JWT verification. There is no impact on confidentiality or integrity, only availability is affected. The vulnerability requires high attack complexity and privileges with user interaction, limiting its exploitability.
Mitigation Recommendations
Upgrade fast-jwt to version 6.2.1 or later where this vulnerability is fixed. Since the vendor advisory indicates the issue is resolved in 6.2.1, applying this official fix is the recommended remediation. No alternative mitigations or workarounds are provided.
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- GitHub_M
- Date Reserved
- 2026-03-31T21:06:06.428Z
- Cvss Version
- 3.1
- State
- PUBLISHED
- Remediation Level
- null
Threat ID: 69d7d5661cc7ad14daeeafcd
Added to database: 4/9/2026, 4:35:50 PM
Last enriched: 4/9/2026, 4:50:50 PM
Last updated: 4/9/2026, 6:15:37 PM
Views: 6
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