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.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- None listed
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
Which versions are affected by CVE-2026-73568?
3 open source packages ship an affected version, including libp2p.
| Package | 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.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2026-73568 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-73568 exists.
Sources
Also known as GHSA-hmj8-5xmh-5573, PYSEC-2026-3681.