CVE-2026-114213 WebSocket 1-byte continuation frames bypass `max_fragmented_message_size` in Bandit
- Exploited in the wild
- Not known
- Fix
- Available
What is CVE-2026-114213?
CVE-2026-114213 is a high-severity vulnerability in mtrudel bandit, published on 26 Oct 2026.
Official description
Allocation of Resources Without Limits or Throttling vulnerability in the WebSocket fragment reassembly of mtrudel bandit allows an unauthenticated remote attacker to exhaust server memory via a fragmented message made of many 1-byte continuation frames.
Bandit.WebSocket.Connection checks max_fragmented_message_size against the payload bytes received, but keeps every non-final continuation frame as a new list cell around its own binary, and nothing limits the number of fragments. A 1-byte fragment costs 7 bytes on the wire but about 150 to 170 bytes of server memory, so one connection can hold about 150 times the configured limit, roughly 1.2 to 1.4 GB at the default 8 MB. Ping frames between fragments keep the connection alive past the idle timeout.
This issue affects bandit: from 1.11.0 before 1.14.0.
Weakness: CWE-770
Which versions are affected by CVE-2026-114213?
1 open source package ship an affected version, including bandit.
| Package | Affected | Fixed in |
|---|---|---|
bandit Hex | From 1.11.0 | 1.14.0 |
How do I fix CVE-2026-114213?
Upgrade bandit to 1.14.0 or later.
Is CVE-2026-114213 being exploited?
There is no known exploitation of CVE-2026-114213 in the wild and no public exploit code.
Sources
Also known as EEF-CVE-2026-114213, GHSA-cpx7-qf6w-jc63, UBUNTU-CVE-2026-114213.