mtrudel bandit up to 1.13.x HPACK encoder connection.ex HPAX.resize header_table_size allocation of resources

Summaryinfo

A vulnerability described as problematic has been identified in mtrudel bandit up to 1.13.x. The affected element is the function HPAX.resize of the file lib/bandit/http2/connection.ex of the component HPACK encoder. Such manipulation of the argument header_table_size leads to allocation of resources. This vulnerability is referenced as CVE-2026-110499. It is possible to launch the attack remotely. No exploit is available. Upgrading the affected component is recommended.

Detailsinfo

A vulnerability was found in mtrudel bandit up to 1.13.x. It has been rated as problematic. Affected by this issue is the function HPAX.resize of the file lib/bandit/http2/connection.ex of the component HPACK encoder. The manipulation of the argument header_table_size with an unknown input leads to a allocation of resources vulnerability. Using CWE to declare the problem leads to CWE-770. The product allocates a reusable resource or group of resources on behalf of an actor without imposing any restrictions on the size or number of resources that can be allocated, in violation of the intended security policy for that actor. Impacted is availability. CVE summarizes:

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.

The advisory is available at github.com. This vulnerability is handled as CVE-2026-110499 since 10/22/2026. The exploitation is known to be easy. The attack may be launched remotely. No form of authentication is required for exploitation. Technical details are known, but there is no available exploit. This vulnerability is assigned to T1499 by the MITRE ATT&CK project.

Upgrading to version 1.14.0 eliminates this vulnerability.

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Productinfo

Vendor

• mtrudel

Name

• bandit

Version

• 1.0
• 1.1
• 1.2
• 1.3
• 1.4
• 1.5
• 1.6
• 1.7
• 1.8
• 1.9
• 1.10
• 1.11
• 1.12
• 1.13

Website

• Product: https://github.com/mtrudel/bandit/

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