Public key confusion in third party block in Biscuit

published 2024-08-05 2 y ago modified 2026-06-17 4 mo ago also EUVD-2024-39567

cvss: 3.0; version 3.1, CNA
cisa kev: Not listed; not in CISA's catalog
epss: 0.3%; EPSS 0.3% chance of exploitation in 30 days, percentile 21%
public exploits: 0; none known

Biscuit is an authorization token with decentralized verification, offline attenuation and strong security policy enforcement based on a logic language. Third-party blocks can be generated without transferring the whole token to the third-party authority. Instead, a `ThirdPartyBlock` request can be sent, providing only the necessary info to generate a third-party block and to sign it: 1. the public key of the previous block (used in the signature), 2. the public keys part of the token symbol table (for public key interning in datalog expressions). A third-part block request forged by a malicious user can trick the third-party authority into generating datalog trusting the wrong keypair. Tokens with third-party blocks containing `trusted` annotations generated through a third party block request. This has been addressed in version 4 of the specification. Users are advised to update their implementations to conform. There are no known workarounds for this vulnerability.

Patch / fix

fixed in 1 links 1

biscuitsec biscuit-auth 5.0.0

github.com/biscuit-auth/biscuit@c87cbb5 commit

CISA SSVC

Exploitation: none
Automatable: no
Technical impact: partial
Assessed: 2 y ago (2024-08-05)

Exploit prediction

0.29% chance of exploitation in the next 30 days, higher than 21% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by	version	score	vector
CNA	3.1	3.0	CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:C/C:N/I:L/A:N

Affected products

biscuit-auth biscuit

Classification

Weakness

CWE-668 Exposure of Resource to Wrong Sphere

References

Sources

CVE List CVE-2024-42350
NVD CVE-2024-42350

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

CPEs and fixed versions use Anchore's correction of NVD's data: Added CPE configurations because not yet analyzed by NVD.

Summary