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Signature forgery in Biscuit

Critical severity GitHub Reviewed Published Jun 11, 2022 in biscuit-auth/biscuit • Updated Mar 7, 2023

Package

cargo biscuit-auth (Rust)

Affected versions

>= 1.0.0, < 2.0.0

Patched versions

2.0.0
maven com.clever-cloud:biscuit-java (Maven)
< 2.0.0
2.0.0
gomod github.com/biscuit-auth/biscuit-go (Go)
< 2.0.0
2.0.0

Description

Impact

The paper Cryptanalysis of Aggregate Γ-Signature and Practical Countermeasures in Application to Bitcoin defines a way to forge valid Γ-signatures, an algorithm that is used in the Biscuit specification version 1.
It would allow an attacker to create a token with any access level.

As Biscuit v1 was still an early version and not broadly deployed, we were able to contact all known users of Biscuit v1 and help them migrate to Biscuit v2.
We are not aware of any active exploitation of this vulnerability.

Patches

The version 2 of the specification mandates a different algorithm than gamma signatures and as such is not affected by this vulnerability. The Biscuit implementations in Rust, Haskell, Go, Java and Javascript all have published versions following the v2 specification.

Workarounds

There is no known workaround, any use of Biscuit v1 should be migrated to v2.

References

Cryptanalysis of Aggregate Γ-Signature and Practical Countermeasures in Application to Bitcoin

For more information

If you have any questions or comments about this advisory:

References

@Geal Geal published to biscuit-auth/biscuit Jun 11, 2022
Published by the National Vulnerability Database Jun 13, 2022
Published to the GitHub Advisory Database Jun 17, 2022
Reviewed Jun 17, 2022
Last updated Mar 7, 2023

Severity

Critical

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v3 base metrics

Attack vector
Network
Attack complexity
Low
Privileges required
None
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS v3 base metrics

Attack vector: More severe the more the remote (logically and physically) an attacker can be in order to exploit the vulnerability.
Attack complexity: More severe for the least complex attacks.
Privileges required: More severe if no privileges are required.
User interaction: More severe when no user interaction is required.
Scope: More severe when a scope change occurs, e.g. one vulnerable component impacts resources in components beyond its security scope.
Confidentiality: More severe when loss of data confidentiality is highest, measuring the level of data access available to an unauthorized user.
Integrity: More severe when loss of data integrity is the highest, measuring the consequence of data modification possible by an unauthorized user.
Availability: More severe when the loss of impacted component availability is highest.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

EPSS score

0.270%
(68th percentile)

Weaknesses

CVE ID

CVE-2022-31053

GHSA ID

GHSA-75rw-34q6-72cr

Source code

Credits

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