High · CVSS 8.7CVE-2026-108529

SETTINGS and stream-0 WINDOW_UPDATE frames trigger quadratic work over blocked streams in BanditCVE-2026-108529

Answer in brief

CVE-2026-108529 records a High severity (CVSS 8.7) vulnerability in SETTINGS and stream-0 WINDOW_UPDATE frames trigger quadratic work over blocked streams in Bandit. The current sources do not mark it as known exploited. The current feed maps mtrudel/bandit (generic), mtrudel/mtrudel/bandit (generic). Check affected ranges and fixed versions before updating.

Analysis pending evidence review

HOL Guard separates source facts from reviewed analysis. See the methodology.

Published Oct 26, 2026Updated Oct 26, 2026Source checked Oct 26, 2026First seen by HOL Oct 26, 2026Material review Oct 26, 2026

Upstream Advisory

Key facts

Risk: High · CVSS 8.7
Exploitation: Not marked as known exploited
Affected software: 2 mapped packages or products
Fix availability: Available

Why this deserves its current priority

CVSS is 8.7. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.

Analysis status

Analysis pending evidence review

Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.

Affected scope and exposure questions

The current feed maps mtrudel/bandit (generic), mtrudel/mtrudel/bandit (generic). Check affected ranges and fixed versions before updating.

Mapped affected packages and fixed versions
Package	Affected range	Fixed version
mtrudel/banditgeneric	>=0.3.4 <1.14.0	1.14.0
mtrudel/mtrudel/banditgeneric	>=6feadb31189d18b7dcda6c663112cd3bbaf63a46 <220b9dfd27f9a21305be2afc75cbe585ddc24e7a	220b9dfd27f9a21305be2afc75cbe585ddc24e7a

Recommended response

Check inventory. Check lockfiles and deployed manifests for mtrudel/bandit, mtrudel/mtrudel/bandit.
Review the reported fix. Source-reported 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.

Evidence timeline and material changes

Published upstream
Oct 26, 2026
Evidence: source:cvelist:source_dates:source-dates:record
Source modified
Oct 26, 2026
Evidence: source:cvelist:source_dates:source-dates:record
First seen by HOL
Oct 26, 2026

Sources and claim methodology

Upstream source 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.

Quoted source text, attributed separately from HOL analysis.