Quick answers
- Is CVE-2026-109584 exploited in the wild?
- No. Junglewise Threat Intelligence has no report of CVE-2026-109584 being exploited in the wild.
- How severe is CVE-2026-109584?
- Informational severity, published 26 October 2026.
- Which products and versions are affected?
- Mtrudel Bandit 0.3.3 to before 1.14.0.
- Is there a fix for CVE-2026-109584?
- Yes: fixed in Bandit 1.14.0. Until then: Configure a finite max_header_list_size value to reject oversized decompressed header lists before memory allocation. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
- How is CVE-2026-109584 attacked?
- It is attacked over the network, in a software library.
- Am I affected by CVE-2026-109584?
- Check whether you run Mtrudel Bandit at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.
How to fix
- Fixed in: Bandit 1.14.0
Configure a finite max_header_list_size value to reject oversized decompressed header lists before memory allocation.
Technical details
The vulnerability is a data amplification attack in HTTP/2 header decompression (HPACK). An attacker crafts a compressed HEADERS frame that stores one large cookie in the HPACK dynamic table, then references it thousands of times using 1-byte indexed fields. Bandit only validates the compressed block size (max_header_block_size) but never enforces the decompressed list limit (max_header_list_size, which defaults to infinity), and the combine_cookie_crumbs function concatenates all cookie fragments into a single binary, amplifying memory consumption. Each concurrent stream can repeat this attack independently.
Affected products
- mtrudel Bandit 0.3.3 to before 1.14.0
Timeline
- 2026-10-26: disclosed