Vulnerability · Published Oct 26, 2026 · Assigned by EEF
CVE-2026-108529SETTINGS and stream-0 WINDOW_UPDATE frames trigger quadratic work over blocked streams in Bandit
High 8.7
In plain English
A high-severity security flaw in bandit from mtrudel. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.6% (higher than 49% of all known vulnerabilities).
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.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu:22.04:LTS | bandit | no fix listed | UBUNTU-CVE-2026-108529 |
| Ubuntu:24.04:LTS | bandit | no fix listed | UBUNTU-CVE-2026-108529 |
| Ubuntu:26.04:LTS | bandit | no fix listed | UBUNTU-CVE-2026-108529 |
| Ubuntu:26.10 | bandit | no fix listed | UBUNTU-CVE-2026-108529 |
Affected products (as reported)
Weakness: CWE-407 · Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N