GHSA-75rw-34q6-72cr — biscuit-auth
CRITICALGHSA-75rw-34q6-72cr is a critical-severity (CVSS 9.8) CWE-347 vulnerability in biscuit-auth. 2 public exploit references exist, so weaponization risk is real. A fix is available for biscuit-auth — see the affected versions and patch details below.
Signature forgery in Biscuit
Exploitation Status
Proof-of-concept exploit code exists
- CISA’s SSVC triage found public proof-of-concept exploit code for this CVE, though no confirmed active exploitation.
- CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
- A successful exploit gives an attacker total control of the affected component, not partial access.
Exploitation and automatability from CISA’s SSVC triage for GHSA-75rw-34q6-72cr.
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
How urgent is this, really
GHSA-75rw-34q6-72cr plotted by exploitation likelihood (EPSS) against impact (CVSS). The shaded corner — EPSS 50%+ and CVSS 7.0+ — is where this CVE doesn't sit, though severity or exploitability alone can still warrant action.
Where this sits among everything scored
Of 377,166 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Real counts from FIRST.org, not a sample — log-scaled since the landscape is heavily right-skewed.
Real-World Exposure
biscuit-auth🐹github.com/biscuit-auth/biscuit-go☕com.clever-cloud:biscuit-javaReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects crates.io, Go, Maven packages — download data is not available via public APIs for these ecosystems.
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:
- Open an issue in biscuit-auth/biscuit
- Ask questions on Matrix
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🦀crates.io | biscuit-auth | ≥ 1.0.0&&< 2.0.0 | 2.0.0cargo update -p biscuit-auth --precise 2.0.0 |
| 🐹Go | github.com/biscuit-auth/biscuit-go | all versions | 2.0.0go get github.com/biscuit-auth/biscuit-go@v2.0.0 |
| ☕Maven | com.clever-cloud:biscuit-java | all versions | 2.0.0com.clever-cloud:biscuit-java:2.0.0 |
Research use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for biscuit-auth, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update biscuit-auth to 2.0.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-75rw-34q6-72cr is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like GHSA-75rw-34q6-72cr can be triaged on real exposure rather than presence alone.
Tailored to GHSA-75rw-34q6-72cr. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is GHSA-75rw-34q6-72cr in your dependencies?
O3 Security finds GHSA-75rw-34q6-72cr across crates.io, Go, Maven dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.