# CVE-2026-33040: libp2p-rust: Gossipsub PRUNE.backoff Duration Overflow

> A remote attacker can crash a libp2p Gossipsub listener by sending a crafted PRUNE message with an excessive backoff value, causing an integer overflow panic.

- **Severity:** High 8.7 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 20 Mar 2026
- **Updated:** 20 Mar 2026
- **Also known as:** GHSA-gc42-3jg7-rxr2, UBUNTU-CVE-2026-33040

## What is CVE-2026-33040?

CVE-2026-33040 is a high-severity vulnerability in rust-libp2p, published on 20 Mar 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

libp2p-rust is the official rust language Implementation of the libp2p networking stack. In versions prior to 0.49.3, the 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. 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. This issue has been fixed in version 0.49.3.

Weakness: CWE-190 (Integer Overflow or Wraparound)

## Which versions are affected by CVE-2026-33040?

2 open source packages ship an affected version, including libp2p-gossipsub. It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `libp2p-gossipsub` | crates.io | All versions | 0.49.3 |
| `libp2p-gossipsub` | crates.io | All versions | 0.49.3 |

Products: Protocol Libp2p-Gossipsub.

## How do I fix CVE-2026-33040?

Upgrade libp2p-gossipsub to 0.49.3 or later.

## Is CVE-2026-33040 being exploited?

There is no known exploitation of CVE-2026-33040 in the wild and no public exploit code.

## Other vulnerabilities in rust-libp2p

- [CVE-2026-34219](https://insights.sbomify.com/CVE-2026-34219/): libp2p-gossipsub: Gossipsub PRUNE Backoff Heartbeat Instant Overflow (high 8.2)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-33040 and fix it if it is affected.

What it is: CVE-2026-33040 is a high-severity vulnerability in rust-libp2p, published on 20 Mar 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-33040 in the wild and no public exploit code.

Affected packages and fixed versions:
- libp2p-gossipsub (crates.io): affected all versions; fixed in 0.49.3
- libp2p-gossipsub (crates.io): affected all versions; fixed in 0.49.3

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-33040/ (Markdown: https://insights.sbomify.com/CVE-2026-33040/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-33040
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-33040
- OSV: https://osv.dev/vulnerability/CVE-2026-33040

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-33040/
Summaries are generated and may contain mistakes; the official description above is the record.