# CVE-2026-31814: Yamux remote Panic via malformed WindowUpdate credit

> A remote attacker can cause a denial of service in the Yamux library by sending a malformed WindowUpdate message that triggers an arithmetic overflow and 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:** 13 Mar 2026
- **Updated:** 13 Mar 2026
- **Also known as:** DEBIAN-CVE-2026-31814, GHSA-4w32-2493-32g7, UBUNTU-CVE-2026-31814

## What is CVE-2026-31814?

CVE-2026-31814 is a high-severity vulnerability in libp2p rust-yamux, published on 13 Mar 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

Yamux is a stream multiplexer over reliable, ordered connections such as TCP/IP. From 0.13.0 to before 0.13.9, a specially crafted WindowUpdate can cause arithmetic overflow in send-window accounting, which triggers a panic in the connection state machine. This is remotely reachable over a normal network connection and does not require authentication. This vulnerability is fixed in 0.13.9.

Weakness: CWE-190 (Integer Overflow or Wraparound)

## Which versions are affected by CVE-2026-31814?

2 open source packages ship an affected version, including yamux. It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `yamux` | crates.io | From 0.13.0 | 0.13.9 |
| `yamux` | crates.io | From 0.13.0 | 0.13.9 |

Products: Protocol Yamux.

## How do I fix CVE-2026-31814?

Upgrade yamux to 0.13.9 or later.

## Is CVE-2026-31814 being exploited?

There is no known exploitation of CVE-2026-31814 in the wild and no public exploit code.

## Other vulnerabilities in libp2p rust-yamux

- [CVE-2026-32314](https://insights.sbomify.com/CVE-2026-32314/): Yamux remote Panic via malformed Data frame with SYN set and len = 262145 (high 8.7)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-31814 and fix it if it is affected.

What it is: CVE-2026-31814 is a high-severity vulnerability in libp2p rust-yamux, published on 13 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-2026-31814 in the wild and no public exploit code.

Affected packages and fixed versions:
- yamux (crates.io): affected from 0.13.0; fixed in 0.13.9
- yamux (crates.io): affected from 0.13.0; fixed in 0.13.9

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-2026-31814/ (Markdown: https://insights.sbomify.com/CVE-2026-31814/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-31814
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-31814
- OSV: https://osv.dev/vulnerability/CVE-2026-31814

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-31814/
Summaries are generated and may contain mistakes; the official description above is the record.