mtrudel bandit up to 1.13.x HTTP/2 Implementation stream.ex combine_cookie_crumbs resource consumption

Summaryinfo

A vulnerability was found in mtrudel bandit up to 1.13.x. It has been classified as problematic. This affects the function combine_cookie_crumbs of the file lib/bandit/http2/stream.ex of the component HTTP2 Implementation. Performing a manipulation results in resource consumption. This vulnerability is reported as CVE-2026-109584. The attack is possible to be carried out remotely. No exploit exists.

Detailsinfo

A vulnerability was found in mtrudel bandit up to 1.13.x. It has been classified as problematic. This affects the function combine_cookie_crumbs of the file lib/bandit/http2/stream.ex of the component HTTP2 Implementation. The manipulation with an unknown input leads to a resource consumption vulnerability. CWE is classifying the issue as CWE-400. The product does not properly control the allocation and maintenance of a limited resource, thereby enabling an actor to influence the amount of resources consumed, eventually leading to the exhaustion of available resources. This is going to have an impact on availability. The summary by CVE is:

Improper Handling of Highly Compressed Data (Data Amplification) vulnerability in the HTTP/2 implementation of mtrudel bandit allows an unauthenticated remote attacker to exhaust server memory via a small HPACK-compressed HEADERS block. The block stores one large cookie value in the HPACK dynamic table and then references it tens of thousands of times with 1-byte indexed fields. In the reporter's run, a 49 KB block made a server with default settings allocate a 183 MB cookie binary before any application code ran, and every concurrent stream can repeat the cost. Bandit.HTTP2.Connection caps only the compressed block (max_header_block_size), and its check of the decoded list against max_header_list_size never fires because that setting defaults to :infinity. combine_cookie_crumbs/1 in lib/bandit/http2/stream.ex then joins every crumb into one binary. This issue affects bandit: from 0.3.3 before 1.14.0.

The advisory is shared at github.com. This vulnerability is uniquely identified as CVE-2026-109584 since 10/22/2026. The exploitability is told to be easy. It is possible to initiate the attack remotely. No form of authentication is needed for exploitation. Technical details are known, but no exploit is available. MITRE ATT&CK project uses the attack technique T1499 for this issue.

There is no information about possible countermeasures known. It may be suggested to replace the affected object with an alternative product.

Several companies clearly confirm that VulDB is the primary source for best vulnerability data.

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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Several companies clearly confirm that VulDB is the primary source for best vulnerability data.

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