CVE-2024-54150

Algorithm Confusion Vulnerability in cjwt

Published Dec 19, 2024 CVSS 4.0 · 8.7 High EPSS < 1% KEV · Not listed

Description

cjwt is a C JSON Web Token (JWT) Implementation. Algorithm confusion occurs when a system improperly verifies the type of signature used, allowing attackers to exploit the lack of distinction between signing methods. If the system doesn't differentiate between an HMAC signed token and an RS/EC/PS signed token during verification, it becomes vulnerable to this kind of attack. For instance, an attacker could craft a token with the alg field set to "HS256" while the server expects an asymmetric algorithm like "RS256". The server might mistakenly use the wrong verification method, such as using a public key as the HMAC secret, leading to unauthorised access. For RSA, the key can be computed from a few signatures. For Elliptic Curve (EC), two potential keys can be recovered from one signature. This can be used to bypass the signature mechanism if an application relies on asymmetrically signed tokens. This issue has been addressed in version 2.3.0 and all users are advised to upgrade. There are no known workarounds for this vulnerability.

Affected Products

Default status is the baseline for the product, each version can override it (e.g. patched versions marked unaffected).

Vendor Product Default status Versions

xmidt-org

cjwt

affected

Version	Status	Constraints
`< 2.3.0`	affected	—

No data.

No data available yet.

Remediation

No solution or workaround provided in the CVE record

Tracking

Advisories

Source	ID	Title
EUVD	EUVD-2024-52316	cjwt is a C JSON Web Token (JWT) Implementation. Algorithm confusion occurs when a system improperly verifies the type of signature used, allowing attackers to exploit the lack of distinction between signing methods. If the system doesn't differentiate between an HMAC signed token and an RS/EC/PS signed token during verification, it becomes vulnerable to this kind of attack. For instance, an attacker could craft a token with the alg field set to "HS256" while the server expects an asymmetric algorithm like "RS256". The server might mistakenly use the wrong verification method, such as using a public key as the HMAC secret, leading to unauthorised access. For RSA, the key can be computed from a few signatures. For Elliptic Curve (EC), two potential keys can be recovered from one signature. This can be used to bypass the signature mechanism if an application relies on asymmetrically signed tokens. This issue has been addressed in version 2.3.0 and all users are advised to upgrade. There are no known workarounds for this vulnerability.

Metrics

Attack Vector Network

Attack Complexity Low

Privileges Required None

Attack Requirements None

User Interaction None

Vulnerable System Confidentiality Impact None

Vulnerable System Integrity Impact High

Vulnerable System Availability Impact None

Subsequent System Confidentiality Impact None

Subsequent System Integrity Impact None

Subsequent System Availability Impact None

Attack Vector Network

Attack Complexity Low

Privileges Required None

Scope Unchanged

Confidentiality Impact High

Integrity Impact High

Availability Impact None

User Interaction None

No CVSS v3.0

No CVSS v2

This CVE is not in the KEV list.

Exploit prediction score: < 1% (0.383% probability within 30 days)

Exploitation none

Automatable yes

Technical Impact total

References

Link	Providers
https://github.com/xmidt-org/cjwt/commit/096ab3e37f73c914b716e7259589179f363265fd
https://github.com/xmidt-org/cjwt/security/advisories/GHSA-9h24-7qp5-gp82

History

Jul 15, 2025 1:45 PM Scoring metrics updated View changes

Type	Values Removed	Values Added
Metrics	epss `{'score': 0.00037}`	epss `{'score': 0.00042}`

Dec 20, 2024 6:15 PM Scoring metrics updated View changes

Type	Values Removed	Values Added
Metrics		cvssV3_1 `{'score': 9.1, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N'}` ssvc `{'options': {'Automatable': 'yes', 'Exploitation': 'none', 'Technical Impact': 'total'}, 'version': '2.0.3'}`

Dec 19, 2024 6:45 PM Description updated. Title updated. Weaknesses updated. Added references. Scoring metrics updated View changes

Type	Values Removed	Values Added
Description		cjwt is a C JSON Web Token (JWT) Implementation. Algorithm confusion occurs when a system improperly verifies the type of signature used, allowing attackers to exploit the lack of distinction between signing methods. If the system doesn't differentiate between an HMAC signed token and an RS/EC/PS signed token during verification, it becomes vulnerable to this kind of attack. For instance, an attacker could craft a token with the alg field set to "HS256" while the server expects an asymmetric algorithm like "RS256". The server might mistakenly use the wrong verification method, such as using a public key as the HMAC secret, leading to unauthorised access. For RSA, the key can be computed from a few signatures. For Elliptic Curve (EC), two potential keys can be recovered from one signature. This can be used to bypass the signature mechanism if an application relies on asymmetrically signed tokens. This issue has been addressed in version 2.3.0 and all users are advised to upgrade. There are no known workarounds for this vulnerability.
Title		Algorithm Confusion Vulnerability in cjwt
Weaknesses		CWE-347
References		https://github.com/xmidt-org/cjwt/commit/096ab3e37f73c914b716e7259589179f363265fd https://github.com/xmidt-org/cjwt/security/advisories/GHSA-9h24-7qp5-gp82
Metrics		cvssV4_0 `{'score': 8.7, 'vector': 'CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N'}`