CVE-2026-108529 SETTINGS and stream-0 WINDOW_UPDATE frames trigger quadratic work over blocked streams in Bandit
- Exploited in the wild
- Not known
- Fix
- Available
What is CVE-2026-108529?
CVE-2026-108529 is a high-severity vulnerability in mtrudel bandit, published on 26 Oct 2026.
Official description
Inefficient Algorithmic Complexity vulnerability in the HTTP/2 implementation of mtrudel bandit allows an unauthenticated remote attacker to exhaust server CPU via small SETTINGS or connection-level WINDOW_UPDATE frames. The attacker opens thousands of streams whose responses block on the connection send window, then sends cheap frames that each make the server walk the whole queue of blocked sends. In the reporter's run, with 3,000 blocked streams a single 9-byte SETTINGS frame took 133 ms to process.
do_pending_sends/2 in lib/bandit/http2/connection.ex retries every queued send and, before each retry, removes that entry from the queue with List.delete/2, so one frame costs O(n²) list operations for n blocked streams. max_concurrent_streams defaults to :infinity, so the attacker chooses n.
This issue affects bandit: from 0.3.4 before 1.14.0.
Weakness: CWE-407
Which versions are affected by CVE-2026-108529?
1 open source package ship an affected version, including bandit.
| Package | Affected | Fixed in |
|---|---|---|
bandit Hex | From 0.3.4 | 1.14.0 |
How do I fix CVE-2026-108529?
Upgrade bandit to 1.14.0 or later.
Is CVE-2026-108529 being exploited?
There is no known exploitation of CVE-2026-108529 in the wild and no public exploit code.
Sources
Also known as EEF-CVE-2026-108529, GHSA-j363-h72p-296m, UBUNTU-CVE-2026-108529.