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CVE-2025-30144— Fast-JWT Improperly Validates iss Claims

Quick assessment

Affected
nearform fast-jwt
Exploitation
Public or AI PoC available; prioritize validation
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

fast-jwt是Nearform开源的一个 JSON Web Token 实现。 fast-jwt 5.0.6之前版本存在安全漏洞，该漏洞源于iss声明验证不当，可能导致伪造JWT。

CVSS 6.5 · Medium EPSS 0.57% · P45

Possible ATT&CK Techniques 1 AI

T1078 · Valid Accounts
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I. Basic Information for CVE-2025-30144

Vulnerability Information
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Vulnerability Title
Fast-JWT Improperly Validates iss Claims
Source: CVE Program / CVE List V5
Vulnerability Description
fast-jwt provides fast JSON Web Token (JWT) implementation. Prior to 5.0.6, the fast-jwt library does not properly validate the iss claim based on the RFC 7519. The iss (issuer) claim validation within the fast-jwt library permits an array of strings as a valid iss value. This design flaw enables a potential attack where a malicious actor crafts a JWT with an iss claim structured as ['https://attacker-domain/', 'https://valid-iss']. Due to the permissive validation, the JWT will be deemed valid. Furthermore, if the application relies on external libraries like get-jwks that do not independently validate the iss claim, the attacker can leverage this vulnerability to forge a JWT that will be accepted by the victim application. Essentially, the attacker can insert their own domain into the iss array, alongside the legitimate issuer, and bypass the intended security checks. This issue is fixed in 5.0.6.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:H/A:N
Source: CVE Program / CVE List V5
Vulnerability Type
对数据真实性的验证不充分
Source: CVE Program / CVE List V5
Vulnerability Title
fast-jwt 安全漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
fast-jwt是Nearform开源的一个 JSON Web Token 实现。 fast-jwt 5.0.6之前版本存在安全漏洞，该漏洞源于iss声明验证不当，可能导致伪造JWT。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
nearform fast-jwt < 5.0.6 -

II. Public POCs for CVE-2025-30144

# POC Description Source Link Shenlong Link
1 None https://github.com/tibrn/CVE-2025-30144 POC Details
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III. Intelligence Information for CVE-2025-30144

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Patches & Fixes for CVE-2025-30144 (1)

Vendor Advisories for CVE-2025-30144 (1)

Other References for CVE-2025-30144 (1)

IV. Related Vulnerabilities

Same product: fast-jwt
Same vendor: nearform
Same weakness: CWE-345

V. Comments for CVE-2025-30144

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