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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

Published
Mar 18, 2026
Updated
Mar 20, 2026
Affected
1 pkg
Patched
1 / 1
Exploits
None indexed
Exploitation data as of Sep 21, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

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

via FIRST.org ↗
0.6%probability of exploitation in next 30 days
Lower Risk0.00%
Lower risk than most CVEs46th percentile — riskier than 46% of all scored CVEsHighest risk

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.

Real-World Exposure

1 pkg affected
🦀libp2p-gossipsub

Real-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:

  1. Establish a standard libp2p transport session and negotiate a stream multiplexer.
  2. Open a Gossipsub stream and negotiate the meshsub protocol.
  3. 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

1 total 1 fixed
EcosystemPackageVulnerable rangeFix
🦀crates.iolibp2p-gossipsuball versions0.49.3cargo update -p libp2p-gossipsub --precise 0.49.3

Detection & mitigation playbook

Open-source dependency

  1. Detect

    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.

  2. 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.

  3. 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.

  4. How O3 protects you

    O3 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like CVE-2026-33040 can be triaged on real exposure rather than presence alone.

Tailored to CVE-2026-33040. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.

Frequently Asked Questions

### 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 s
O3 Security · Impact-Aware SCA

Is CVE-2026-33040 in your dependencies?

O3 Security finds CVE-2026-33040 across crates.io dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.

Scan my dependencies How O3 SCA works
CVE-2026-33040: libp2p-gossipsub DoS | O3 Security