CVE-2026-108529 | BDVDB-2026-395607 Detail
mtrudelbandit
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.
Impact#
An unauthenticated remote client that keeps thousands of HTTP/2 response streams blocked makes each 9-byte SETTINGS or stream-0 WINDOW_UPDATE frame cost the server quadratic CPU work. A steady trickle of such frames keeps the connection process, and the scheduler running it, busy for as long as the attacker continues.
Weaknesses#
- CWE-407 Inefficient Algorithmic Complexity
References#
- https://github.com/mtrudel/bandit/security/advisories/GHSA-j363-h72p-296m
- https://cna.erlef.org/cves/CVE-2026-108529.html
- https://osv.dev/vulnerability/EEF-CVE-2026-108529
- https://github.com/mtrudel/bandit/commit/6feadb31189d18b7dcda6c663112cd3bbaf63a46
- https://github.com/mtrudel/bandit/commit/220b9dfd27f9a21305be2afc75cbe585ddc24e7a
Exploit#
No public exploit known
History#
- Version 1Record published in the CVE List.