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CVE-2026-42788— HTTP/2 frame size limit checked after body is buffered 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.

Bandit是Mat Trudel个人开发者的一款高性能HTTP与WebSocket服务器。 Bandit 0.3.6版本至1.11.0之前版本存在安全漏洞，该漏洞源于HTTP/2帧反序列化时在检查大小限制前缓冲整个帧体，可能导致未经身份验证的内存耗尽。

AI Predicted 7.5 Difficulty: Moderate EPSS 0.55% · P44

Possible ATT&CK Techniques 1 AI

T1499.002 · Service Exhaustion Flood

Affected Version Matrix 2

VendorProduct Version RangeStatus
mtrudel bandit 0.3.6< 1.11.0 affected
f00dd69a5b2a4863be585907acd853c4ffd41399< 1e8e55966da9129016b73d32f0e1df4630e3b463 affected
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I. Basic Information for CVE-2026-42788

Vulnerability Information
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Vulnerability Title
HTTP/2 frame size limit checked after body is buffered in bandit
Source: CVE Program / CVE List V5
Vulnerability Description
Allocation of Resources Without Limits or Throttling vulnerability in mtrudel bandit allows unauthenticated memory exhaustion via oversized HTTP/2 frames. 'Elixir.Bandit.HTTP2.Frame':deserialize/2 in lib/bandit/http2/frame.ex checks the SETTINGS_MAX_FRAME_SIZE limit only after pattern-matching payload::binary-size(length), which requires the entire frame body to be present in memory before either the accept or reject clause can fire. A peer that announces a frame length up to the 24-bit maximum (~16 MiB) causes the server to buffer that entire body before the size guard is evaluated, regardless of the max_frame_size negotiated during the HTTP/2 handshake (default 16 KiB per RFC 9113). An unauthenticated attacker holding many concurrent connections can force the server to buffer far more memory than the negotiated frame size limit should permit, leading to memory pressure and potential denial of service. This issue affects bandit: from 0.3.6 before 1.11.0.
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:L/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
Vulnerability Title
Bandit 安全漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Bandit是Mat Trudel个人开发者的一款高性能HTTP与WebSocket服务器。 Bandit 0.3.6版本至1.11.0之前版本存在安全漏洞，该漏洞源于HTTP/2帧反序列化时在检查大小限制前缓冲整个帧体，可能导致未经身份验证的内存耗尽。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
mtrudel bandit 0.3.6 ~ 1.11.0 cpe:2.3:a:mtrudel:bandit:*:*:*:*:*:*:*:*
mtrudel bandit f00dd69a5b2a4863be585907acd853c4ffd41399 ~ 1e8e55966da9129016b73d32f0e1df4630e3b463 cpe:2.3:a:mtrudel:bandit:*:*:*:*:*:*:*:*

II. Public POCs for CVE-2026-42788

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III. Intelligence Information for CVE-2026-42788

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Patches & Fixes for CVE-2026-42788 (1)

Vendor Advisories for CVE-2026-42788 (3)

Same Patch Batch · mtrudel · 2026-05-01 · 5 CVEs total

CVE-2026-39805 6.3 MEDIUM CL.CL HTTP request smuggling via duplicate Content-Length in bandit
CVE-2026-42786 WebSocket fragmented message reassembly unbounded in bandit
CVE-2026-39807 Client-supplied URI scheme trusted without transport verification in bandit
CVE-2026-39804 WebSocket permessage-deflate inflate has no output-size cap in bandit

IV. Related Vulnerabilities

Same product: bandit
Same vendor: mtrudel
Same weakness: CWE-770

V. Comments for CVE-2026-42788

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