CVE-2023-48223CWE-20

fast-jwt JWT Algorithm Confusion

Medium · published November 20, 2023

CVSS v3.1
5.9
EPSS
1%
Percentile
51.9
In the wild
Unconfirmed
What it is

fast-jwt provides fast JSON Web Token (JWT) implementation. Prior to version 3.3.2, the fast-jwt library does not properly prevent JWT algorithm confusion for all public key types. The 'publicKeyPemMatcher' in 'fast-jwt/src/crypto.js' does not properly match all common PEM formats for public keys. To exploit this vulnerability, an attacker needs to craft a malicious JWT token containing the HS256 algorithm, signed with the public RSA key of the victim application. This attack will only work if the victim application utilizes a public key containing the `BEGIN RSA PUBLIC KEY` header. Applications using the RS256 algorithm, a public key with a `BEGIN RSA PUBLIC KEY` header, and calling the verify function without explicitly providing an algorithm, are vulnerable to this algorithm confusion attack which allows attackers to sign arbitrary payloads which will be accepted by the verifier. Version 3.3.2 contains a patch for this issue. As a workaround, change line 29 of `blob/master/src/crypto.js` to include a regular expression.

The record
Technical detail
CVSS v3.1
5.9 · MEDIUM
Vector
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N
CVSS v4.0
Not supplied
EPSS
0.00681 · 51.9th percentile
Weakness
CWE-20 · Improper Input Validation
Published
2023-11-20T17:39Z
EPSS history
Timeline
  • 20 NOV 17:39Z
    fast-jwt JWT Algorithm Confusion
    cvelistv5