# CVE-2026-73568: py-libp2p: yamux connection DoS via oversized data frame

> An attacker can cause a denial of service in py-libp2p by sending oversized yamux data frames, blocking all streams on the connection.

- **Severity:** High 7.5 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 13 Aug 2026
- **Updated:** 13 Aug 2026
- **Also known as:** GHSA-hmj8-5xmh-5573, PYSEC-2026-3681

## What is CVE-2026-73568?

CVE-2026-73568 is a high-severity denial of service vulnerability in py-libp2p, published on 13 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

py-libp2p is the Python implementation of the libp2p networking stack. In 0.7.0 and earlier, the yamux handle_incoming() method in libp2p/stream_muxer/yamux/yamux.py reads an attacker-controlled 32-bit DATA frame length with read_exactly() before validating it against MAX_WINDOW_SIZE or checking whether stream_id exists. A peer that completes the standard Noise handshake can send a 12-byte frame declaring a 0xFFFFFFFF body and then withhold the body, causing the sequential yamux read loop used by the default new_host() configuration to block and preventing every stream on that connection from making progress. No fixed version is available as of this review.

Weakness: CWE-400 (Uncontrolled Resource Consumption)

## Which versions are affected by CVE-2026-73568?

3 open source packages ship an affected version, including libp2p.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `libp2p` | PyPI | All versions to 0.7.0 | None |
| `libp2p` | PyPI | All versions to 0.7.0 | None |
| `libp2p` | PyPI | All versions to 0.7.0 | None |

## How do I fix CVE-2026-73568?

No fix has been published for CVE-2026-73568 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-73568 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-73568 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-73568 and fix it if it is affected.

What it is: CVE-2026-73568 is a high-severity denial of service vulnerability in py-libp2p, published on 13 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-73568 exists.

Affected packages and fixed versions:
- libp2p (PyPI): affected all versions up to 0.7.0; no fix listed
- libp2p (PyPI): affected all versions up to 0.7.0; no fix listed
- libp2p (PyPI): affected all versions up to 0.7.0; no fix listed

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-2026-73568/ (Markdown: https://insights.sbomify.com/CVE-2026-73568/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-73568
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-73568
- OSV: https://osv.dev/vulnerability/CVE-2026-73568

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-73568/
Summaries are generated and may contain mistakes; the official description above is the record.