libp2p: yamux connection DoS via oversized data frame

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

7.5 · CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

EPSS

• CVE-2026-73568: 0.49% estimated exploitation activity in the next 30 days; percentile 42.05 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Summary The yamux stream multiplexer in py-libp2p does not validate incoming DATA frame lengths against the receive window before reading the frame body. Any peer that completes a standard libp2p handshake can send a single 12-byte frame claiming a 4 GB body, causing the victim's yamux read loop to block indefinitely. This affects the default newhost() configuration and requires no special setup on either side. Details In libp2p/streammuxer/yamux/yamux.py (lines 915 to 926), the handleincoming() method dispatches on frame type. When a DATA frame arrives, it reads the body unconditionally: The length field is taken directly from the wire-decoded frame header, a 32-bit unsigned integer with a maximum value of 4,294,967,295. There is no check that length fits within the stream's receive window (DEFAULTWINDOWSIZE = 256 1024 bytes). The body read also happens before the code checks whether the referenced streamid even exists in self.streams (that check is at line 954), so any stream ID…

Published by the source

24 Jul 2026, 22:37 UTC

Last modified by the source

19 Aug 2026, 12:56 UTC

Source last checked

26 Oct 2026, 13:50 UTC

1. Revision 2 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-hmj8-5xmh-5573

2. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-hmj8-5xmh-5573

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# Patch Next advisory brief: CVE-2026-73568

Advisory: libp2p: yamux connection DoS via oversized data frame
IDs: CVE-2026-73568, GHSA-hmj8-5xmh-5573
Record: https://patchnext.com/advisories/cve-2026-73568 (revision 2, source checked 26 Oct 2026, 13:50 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 7.5)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor response not established. A vendor fix does not mean a deployment is fixed.

## Affected components
- PyPI libp2p: affected <= 0.7.0

## Suggested inspection (read-only)
- `python -m pip show libp2p`: prints the installed version. Run with the environment that serves production active.

## Supported action
No complete vendor fix is recorded. Follow the primary source's mitigation guidance and check this record again before closing anything.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on libp2p.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/GHSA-hmj8-5xmh-5573 (OSV record GHSA-hmj8-5xmh-5573 lists affected ranges: PyPI libp2p >=0 <=0.7.0)
- Verified: https://github.com/advisories/GHSA-hmj8-5xmh-5573 (GitHub-reviewed advisory GHSA-hmj8-5xmh-5573 lists affected ranges: PyPI libp2p >=0 <=0.7.0)

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