CVE-2026-110499
Client-chosen HPACK encoder table size is applied uncapped, growing per-connection state with every response in Bandit
- State
- Published
- Severity
- 8.7 High
- Published
- Oct 26, 2026
- Updated
- Oct 26, 2026
- Reserved
- Oct 22, 2026
Description
Allocation of Resources Without Limits or Throttling vulnerability in the HTTP/2 implementation of mtrudel bandit allows an unauthenticated remote attacker to grow per-connection memory and CPU cost without bound via a large SETTINGS_HEADER_TABLE_SIZE. Bandit resizes its HPACK encoder table to whatever size the client advertises, up to 2^32-1 bytes, and indexes response headers into it. Because responses carry distinct values such as date or content-length, nothing is evicted and the table grows with every response for the life of the connection, while each lookup scans it linearly.
The SETTINGS handling in Bandit.HTTP2.Connection (lib/bandit/http2/connection.ex) passes remote_settings.header_table_size to HPAX.resize/2 with no server-side cap, and encode_headers encodes every response header as :store. Serving N responses on one connection therefore costs O(N²) CPU in the connection process.
This issue affects bandit: from 0.3.6 before 1.14.0.
Scores
| CVSS | Score | Vector | Source |
|---|---|---|---|
| 4.0 | 8.7 High | 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 | EEF |
Weaknesses
- CWE-770 Allocation of Resources Without Limits or Throttling
Affected Products
| Product | Versions |
|---|---|
banditmtrudel |
|
banditmtrudel |
|
References
- Client-chosen HPACK encoder table size is applied uncapped, growing per-connection state with every response in Banditvendor-advisoryrelated
- EEF CNA record for CVE-2026-110499related
- OSV record EEF-CVE-2026-110499related
- Introducing commit 0e68313 in mtrudel/banditrelated
- Fix commit 220b9df in mtrudel/banditpatch
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