How severe is CVE-2023-39533?

CVE-2023-39533 has a CVSS score of 7.5/10, rated HIGH. Immediate patching is strongly recommended.

Which packages are affected by CVE-2023-39533?

CVE-2023-39533 affects the following packages: github.com/libp2p/go-libp2p (Go), github.com/libp2p/go-libp2p (Go), github.com/libp2p/go-libp2p (Go). Ecosystems affected: Go.

How do I fix CVE-2023-39533?

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 CVE-2023-39533 is resolved across your whole dependency graph.

How do I detect CVE-2023-39533 in my Go dependencies?

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.

How do I mitigate CVE-2023-39533 if there is no patch (or I can't update yet)?

Cap what an attacker can consume: apply request size, rate and timeout limits in front of the affected component, and run it with memory and CPU limits so exhaustion degrades one worker rather than the whole service.

Is CVE-2023-39533 actively exploited in the wild?

Yes. There are 1 known exploit references for CVE-2023-39533, including 1 in-the-wild exploitation observed on GitHub and other sources. Treat this as actively exploitable and prioritize patching immediately. All exploit code should only be run in an isolated sandbox environment for research or authorized testing — never against production systems without explicit written authorization.

What is the EPSS score for CVE-2023-39533?

CVE-2023-39533 has an EPSS (Exploit Prediction Scoring System) score of 1.5%, placing it in the 75th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is CVE-2023-39533?

CVE-2023-39533 is classified as CWE-770 (CWE-770). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

When was CVE-2023-39533 published, and has it been updated?

CVE-2023-39533 was published on August 8, 2023 and was last updated on October 28, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

🐹

🐹 Go

Not in CISA KEV

HIGH severity

CVE-2023-39533 — go-libp2p

HIGHFix: golang/go@2350afd

CVE-2023-39533 is a high-severity (CVSS 7.5) CWE-770 vulnerability in github.com/libp2p/go-libp2p. 1 public exploit or proof-of-concept reference is indexed, 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

Also known asGHSA-876p-8259-xjggGO-2023-2000

Published

Aug 8, 2023

Updated

Oct 28, 2026

Affected

3 pkgs

Patched

3 / 3

Exploits

1 known

Exploitation data as of Nov 4, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

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 CVE-2023-39533.

EPSS Exploitation Probability

via FIRST.org ↗

1.5%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs75th percentile — riskier than 75% of all scored CVEsHighest risk

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

Where this sits among everything scored

Real-World Exposure

3 pkgs affected

🐹github.com/libp2p/go-libp2p🐹github.com/libp2p/go-libp2p🐹github.com/libp2p/go-libp2p

Real-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

3 total 3 fixed

Ecosystem	Package	Vulnerable range	Fix
🐹Go	`github.com/libp2p/go-libp2p`	all versions	0.27.8`go get github.com/libp2p/go-libp2p@v0.27.8`
🐹Go	`github.com/libp2p/go-libp2p`	≥ 0.28.0&&< 0.28.2	0.28.2`go get github.com/libp2p/go-libp2p@v0.28.2`
🐹Go	`github.com/libp2p/go-libp2p`	≥ 0.29.0&&< 0.29.1	0.29.1`go get github.com/libp2p/go-libp2p@v0.29.1`

Affected Products

1 product · 3 configurations

Application

go-libp2plibp2p

≥ 0.28.0 && < 0.28.2

1 version

0.29.0

Exploits & PoCs

Research use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.

go-libp2p is the Go implementation of the libp2p Networking Stack. Prior…

github.comNVDAug 2023

Detection & mitigation playbook

Open-source dependency

Detect
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 CVE-2023-39533 is resolved across your whole dependency graph.
Workarounds
Cap what an attacker can consume: apply request size, rate and timeout limits in front of the affected component, and run it with memory and CPU limits so exhaustion degrades one worker rather than the whole service.

Frequently Asked Questions

### 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 G