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.
Analysis and contextual insights are available on OpenCVE Cloud.
Vendor Workaround
From 1.9.0, bound the number of streams a client can open, for example with http_2_options: [default_local_settings: [max_concurrent_streams: 100]], which bounds the work each frame can cause. From 0.7.0, disabling HTTP/2 with http_2_options: [enabled: false] removes the vulnerable path.
Tracking
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No advisories yet.
Mon, 26 Oct 2026 16:30:00 +0000
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ssvc
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Mon, 26 Oct 2026 14:00:00 +0000
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| 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. | |
| Title | SETTINGS and stream-0 WINDOW_UPDATE frames trigger quadratic work over blocked streams in Bandit | |
| First Time appeared |
Mtrudel
Mtrudel bandit |
|
| Weaknesses | CWE-407 | |
| CPEs | cpe:2.3:a:mtrudel:bandit:*:*:*:*:*:*:*:* | |
| Vendors & Products |
Mtrudel
Mtrudel bandit |
|
| References |
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|
| Metrics |
cvssV4_0
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Status: PUBLISHED
Assigner: EEF
Published:
Updated: 2026-10-26T15:35:50.781Z
Reserved: 2026-10-12T16:15:01.628Z
Link: CVE-2026-108529
Updated: 2026-10-26T15:32:23.882Z
Status : Awaiting Analysis
Published: 2026-10-26T14:16:24.733
Modified: 2026-10-26T16:59:16.113
Link: CVE-2026-108529
No data.
OpenCVE Enrichment
Updated: 2026-10-26T15:45:12Z
