CVE-2026-33040 — libp2p-gossipsub
CVE-2026-33040 is a CWE-190 vulnerability in libp2p-gossipsub. A fix is available for libp2p-gossipsub — see the affected versions and patch details below.
Gossipsub PRUNE.backoff Duration Overflow
Exploitation Status
No confirmed exploitation observed yet
- CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
- CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.
Exploitation and automatability from CISA’s SSVC triage for CVE-2026-33040.
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
Real-World Exposure
libp2p-gossipsubReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects crates.io packages — download data is not available via public APIs for these ecosystems.
Description
Summary
The Rust libp2p Gossipsub implementation accepts attacker-controlled PRUNE backoff values and may perform unchecked time arithmetic when storing backoff state. A specially crafted PRUNE control message with an extremely large backoff (e.g. u64::MAX) can lead to Duration/Instant overflow during backoff update logic, triggering a panic in the networking state machine. This is remotely reachable over a normal libp2p connection and does not require authentication.
Attack Scenario
An attacker that can establish a libp2p Gossipsub session with a target node can crash the target by sending a single crafted PRUNE control message:
- Establish a standard libp2p transport session and negotiate a stream multiplexer.
- Open a Gossipsub stream and negotiate the meshsub protocol.
- Send one protobuf RPC containing ControlPrune with a very large backoff value (e.g. 18446744073709551615 / u64::MAX). When processed, the oversized backoff can reach time-update logic that adds Duration::from_secs(backoff) to Instant::now(), causing overflow and panic.
Impact
Remote unauthenticated denial of service. Any application exposing a libp2p Gossipsub listener and using the affected backoff-handling path can be crashed by a network attacker that can reach the service port. The attack can be repeated by reconnecting and replaying the crafted control message.
Patches
Users should upgrade to a release that hardens Gossipsub backoff handling.
This vulnerability was originally submitted by @revofusion to the Ethereum Foundation bug bounty program
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🦀crates.io | libp2p-gossipsub | all versions | 0.49.3cargo update -p libp2p-gossipsub --precise 0.49.3 |
Affected Products
libp2p-gossipsubprotocolDetection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for libp2p-gossipsub, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update libp2p-gossipsub to 0.49.3 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-33040 is resolved across your whole dependency graph.
Workarounds
Stop feeding it untrusted input: reject or quarantine files and payloads from unverified sources until you can upgrade, restrict accepted formats to the ones you actually need, and run the parsing or decoding step in a least-privileged sandbox or short-lived worker so a crash or corrupted read cannot reach the rest of the process.
Frequently Asked Questions
Is CVE-2026-33040 in your dependencies?
Find it across crates.io, including transitive dependencies.