Quick answers
- Is CVE-2026-65623 exploited in the wild?
- No. Junglewise Threat Intelligence has no report of CVE-2026-65623 being exploited in the wild.
- How severe is CVE-2026-65623?
- Informational severity, with a CVSS score of 8.7, published 24 July 2026.
- Which products and versions are affected?
- Mat Trudel Bandit >= 1.11.0, < 1.12.1.
- Is there a fix for CVE-2026-65623?
- A patch was published on 2026-07-24: Fix committed in version 1.12.1 Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
- How is CVE-2026-65623 attacked?
- It is attacked over the network, in a software library.
- Am I affected by CVE-2026-65623?
- Check whether you run Mat Trudel Bandit at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.
Technical details
An Inefficient Algorithmic Complexity (CWE-407) vulnerability exists in Bandit's WebSocket fragment reassembly logic. The 'oversize_message?/2' guard in 'lib/bandit/websocket/connection.ex' appends non-final continuation frames to a left-nested iolist and subsequently calls 'IO.iodata_length/1' on the entire accumulated buffer for every new frame. This results in quadratic (O(n^2)) computational complexity relative to the number of frames. While the 'max_fragmented_message_size' (default 8 MB) limits the total byte size, it does not limit the frame count; an attacker can send millions of 1-byte frames to pin a CPU core for extended periods. The issue is exacerbated because the WebSocket read timeout is an idle timeout and cannot preempt the synchronous reassembly work. The vulnerability is fixed in version 1.12.1.
Affected products
- mtrudel bandit >= 1.11.0, < 1.12.1
Timeline
- 2026-07-24: advisory: GHSA-vg8x-66vg-5pxh published
- 2026-07-24: patched: Fix committed in version 1.12.1