GHSA-876p-8259-xjgg is a high-severity (CVSS 7.5) CWE-770 vulnerability in github.com/libp2p/go-libp2p. 1 public exploit reference exists, so weaponization risk is real. A fix is available for github.com/libp2p/go-libp2p — see the affected versions and patch details below.
libp2p nodes vulnerable to attack using large RSA keys
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.
Exploitation and automatability from CISA’s SSVC triage for GHSA-876p-8259-xjgg.
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-876p-8259-xjgg 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 377,238 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
github.com/libp2p/go-libp2p🐹github.com/libp2p/go-libp2p🐹github.com/libp2p/go-libp2pReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects Go packages — download data is not available via public APIs for these ecosystems.
Description
Impact
A malicious peer can use large RSA keys to run a resource exhaustion attack & force a node to spend time doing signature verification of the large key. This vulnerability is present in the core/crypto module of go-libp2p and can occur during the Noise handshake and the libp2p x509 extension verification step. To prevent this attack, go-libp2p now restricts RSA keys to <= 8192 bits.
Patches
Users should upgrade their go-libp2p versions to >=v0.27.8, >= v0.28.2, or >=v0.29.1 To protect your application, it's necessary to update to these patch releases AND to use the updated Go compiler (1.20.7 or 1.19.12, respectively)
Workarounds
There are no known workarounds
References
The Golang crypto/tls package also had this vulnerability ("verifying certificate chains containing large RSA keys is slow” https://github.com/golang/go/issues/61460) Fix in golang/go crypto/tls: https://github.com/golang/go/commit/2350afd2e8ab054390e284c95d5b089c142db017 Fix in quic-go https://github.com/quic-go/quic-go/pull/4012
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐹Go | github.com/libp2p/go-libp2p | all versions | 0.27.8go get github.com/libp2p/go-libp2p@v0.27.8 |
| 🐹Go | github.com/libp2p/go-libp2p | ≥ 0.28.0&&< 0.28.2 | 0.28.2go get github.com/libp2p/go-libp2p@v0.28.2 |
| 🐹Go | github.com/libp2p/go-libp2p | ≥ 0.29.0&&< 0.29.1 | 0.29.1go get github.com/libp2p/go-libp2p@v0.29.1 |
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 github.com/libp2p/go-libp2p, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update github.com/libp2p/go-libp2p to 0.27.8 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-876p-8259-xjgg 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-876p-8259-xjgg can be triaged on real exposure rather than presence alone.
Tailored to GHSA-876p-8259-xjgg. 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-876p-8259-xjgg in your dependencies?
O3 Security finds GHSA-876p-8259-xjgg across Go dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.