CVE-2026-110499— Client-chosen HPACK encoder table size is applied uncapped, growing per-connection state with every response in Bandit

Quick assessment

Affected

mtrudel bandit

Exploitation

No confirmed in-the-wild exploitation; assess based on exposure

Recommended action

Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

在 mtrudel 开发的 Bandit 库的 HTTP/2 实现中，存在一个“无限制或无节流地分配资源”的漏洞。该漏洞允许未认证的远程攻击者通过设置一个巨大的值，使每个连接上的内存和 CPU 消耗无限制地增长。Bandit 会根据客户端通告的大小调整其 HPACK 编码器表，上限可达 $2^{32}-1$ 字节，并将响应头索引到该表中。由于响应中携带的值（如日期、内容长度等）各不相同，表中的条目永远不会被移除，导致该表在连接的整个生命周期内随每次响应持续增长；而每次查找操作均需线性扫描整个表。在（文件：）

CVSS 8.7 · High Updated Oct 26, 2026

Possible ATT&CK Techniques 1 AI

T1190 · Exploit Public-Facing Application

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Vulnerability Information

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Vulnerability Title

Client-chosen HPACK encoder table size is applied uncapped, growing per-connection state with every response in Bandit

Source: CVE Program / CVE List V5

Vulnerability 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.

Source: CVE Program / CVE List V5

CVSS Information

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

Source: CVE Program / CVE List V5

Vulnerability Type

不加限制或调节的资源分配

Source: CVE Program / CVE List V5

Affected Products

Vendor	Product	Affected Versions	CPE	Subscribe
mtrudel	bandit	0.3.6 ~ 1.14.0	`cpe:2.3:a:mtrudel:bandit::::::::`
mtrudel	bandit	0e68313fab9d204257ebad5c447e4cd9cea8e0ea ~ 220b9dfd27f9a21305be2afc75cbe585ddc24e7a	`cpe:2.3:a:mtrudel:bandit::::::::`

II. Public POCs for CVE-2026-110499

#	POC Description	Source Link	Shenlong Link

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III. Intelligence Information for CVE-2026-110499

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Other References for CVE-2026-110499 (5)

https://osv.dev/vulnerability/EEF-CVE-2026-110499 related
https://cna.erlef.org/cves/CVE-2026-110499.html related
https://github.com/mtrudel/bandit/commit/220b9dfd27f9a21305be2afc75cbe585ddc24e7a patch
https://github.com/mtrudel/bandit/commit/0e68313fab9d204257ebad5c447e4cd9cea8e0ea related
https://github.com/mtrudel/bandit/security/advisories/GHSA-47x4-3fxf-82fr vendor-advisory related

https://www.cve.org/CVERecord?id=CVE-2026-110499

Same Patch Batch · mtrudel · 2026-10-26 · 11 CVEs total

CVE-2026-114213	8.7 HIGH	WebSocket 1-byte continuation frames bypass `max_fragmented_message_size` in Bandit
CVE-2026-109584	8.7 HIGH	HTTP/2 cookie crumb join expands a small HPACK header block into an unbounded allocation i
CVE-2026-111101	8.7 HIGH	HTTP/1.1 chunked request bodies made of 1-byte chunks amplify memory use in Bandit
CVE-2026-113436	8.7 HIGH	Quadratic bignum parsing of Content-Length and Host port values in Bandit
CVE-2026-108529	8.7 HIGH	SETTINGS and stream-0 WINDOW_UPDATE frames trigger quadratic work over blocked streams in
CVE-2026-108525	8.7 HIGH	HTTP/2 inbound flow control is not enforced, letting a client queue unbounded DATA in stre
CVE-2026-115269	8.7 HIGH	HTTP/2 WINDOW_UPDATE and SETTINGS frames reset the request body read timeout in Bandit
CVE-2026-111103	8.2 HIGH	HTTP/2 StreamError recovery rolls back connection state and bypasses per-connection limits
CVE-2026-114216	6.3 MEDIUM	Chunk extensions accept bare LF and CR, enabling request smuggling in Bandit
CVE-2026-110314	6.3 MEDIUM	WebSocket frames keep reaching the WebSock after a server-initiated close in Bandit

IV. Related Vulnerabilities

Same product: bandit

Same vendor: mtrudel

Same weakness: CWE-770