Summary
libp2p-quic: Remote panic via certificate expiry race during QUIC handshake
libp2p-quic can panic on an inbound QUIC handshake if a malicious peer presents a valid, short lived libp2p TLS certificate and delays the final TLS 1.3 handshake fragment until the certificate expires.
This is remotely reachable by a network peer and can crash applications exposing a libp2p QUIC listener.
Details
During the TLS handshake, libp2p-tls parses and validates the peer certificate. After Quinn reports handshake completion, libp2p-quic re-parses the same certificate in the post-handshake upgrade path and assumes this cannot fail:
However, libp2p_tls::certificate::parse() re-runs certificate verification on every call, including a wall-clock validity check. A certificate that was valid during the first handshake time parse can expire before the second post-handshake parse, causing the expect(...) to panic.
PoC
A malicious peer can trigger this by:
- Opening a QUIC connection to a libp2p QUIC listener.
- Presenting a valid libp2p TLS certificate with a very short lifetime.
- Allowing the initial handshake-time certificate validation to succeed.
- Withholding the final client handshake fragment packet until after the certificate expires, but before the QUIC handshake timeout elapses.
- The listener completes the handshake and hits the post-handshake certificate re-parse, which panics.
Impact
Remote unauthenticated denial of service. Any application exposing an affected libp2p-quic listener can be crashed by a network peer that performs a valid-looking QUIC/TLS handshake with attacker-controlled timing. No malformed packets are required.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
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Frequently Asked Questions
- What is CVE-2026-61544? CVE-2026-61544 is a high-severity security vulnerability in libp2p-quic (rust), affecting versions < 0.13.1. It is fixed in 0.13.1.
- Which versions of libp2p-quic are affected by CVE-2026-61544? libp2p-quic (rust) versions < 0.13.1 is affected.
- Is there a fix for CVE-2026-61544? Yes. CVE-2026-61544 is fixed in 0.13.1. Upgrade to this version or later.
- Is CVE-2026-61544 exploitable, and should I be worried? Whether CVE-2026-61544 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether CVE-2026-61544 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
- How do I fix CVE-2026-61544? Upgrade
libp2p-quicto 0.13.1 or later.