Goal Reached Thanks to every supporter — we hit 100%!

Goal: 1000 CNY · Raised: 1359 CNY

100%
Buy Us a Coffee

CVE-2026-39803— HTTP/1 chunked body reader ignores length cap 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 1.4.0版本至1.11.1之前版本存在安全漏洞，该漏洞源于资源分配无限制，可能导致未经身份验证的远程攻击者通过内存耗尽造成拒绝服务。

AI Predicted 7.5 Difficulty: Trivial EPSS 0.97% · P61

Possible ATT&CK Techniques 1 AI

T1496 · Resource Hijacking

Affected Version Matrix 2

VendorProduct Version RangeStatus
mtrudel bandit 1.4.0< 1.11.1 affected
903e209a521bc216b9f9065c01ae9a0cac2d5a10< ae3520dfdbfab115c638f8c7f6f6b805db34e1ab affected
Get alerts for future matching vulnerabilities Log in to subscribe

I. Basic Information for CVE-2026-39803

Vulnerability Information
Have questions about the vulnerability? See if Shenlong's analysis helps!
View Shenlong Deep Dive ↗

Although we use advanced large model technology, its output may still contain inaccurate or outdated information.Shenlong tries to ensure data accuracy, but please verify and judge based on the actual situation.

Vulnerability Title
HTTP/1 chunked body reader ignores length cap in bandit
Source: CVE Program / CVE List V5
Vulnerability Description
Allocation of Resources Without Limits or Throttling vulnerability in mtrudel bandit allows unauthenticated remote denial of service via memory exhaustion. The chunked clause of 'Elixir.Bandit.HTTP1.Socket':read_data/2 in lib/bandit/http1/socket.ex ignores the caller-supplied :length option when reading HTTP/1 chunked request bodies. Instead of capping the accumulated body at the configured limit (e.g. Plug.Parsers' default 8 MB), do_read_chunked_data!/5 buffers every received chunk into an iolist unconditionally and materializes the entire body as a single binary. The function always returns {:ok, body, ...}, so callers cannot interpose a 413 response. Because Plug.Parsers runs before routing and authentication in the standard Phoenix endpoint, an unauthenticated attacker needs no valid route or credentials. Sending a single Transfer-Encoding: chunked POST request with an arbitrarily large body to any path causes the BEAM process to exhaust available memory and be terminated by the OS OOM killer. The content-length path in the same function correctly enforces the limit and is not affected. This issue affects bandit: from 1.4.0 before 1.11.1.
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
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 1.4.0版本至1.11.1之前版本存在安全漏洞，该漏洞源于资源分配无限制，可能导致未经身份验证的远程攻击者通过内存耗尽造成拒绝服务。
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 1.4.0 ~ 1.11.1 cpe:2.3:a:mtrudel:bandit:*:*:*:*:*:*:*:*
mtrudel bandit 903e209a521bc216b9f9065c01ae9a0cac2d5a10 ~ ae3520dfdbfab115c638f8c7f6f6b805db34e1ab cpe:2.3:a:mtrudel:bandit:*:*:*:*:*:*:*:*

II. Public POCs for CVE-2026-39803

# POC Description Source Link Shenlong Link
AI-Generated POC Premium

No public POC found.

Login to generate AI POC

III. Intelligence Information for CVE-2026-39803

请登录查看更多情报信息。

Patches & Fixes for CVE-2026-39803 (1)

Vendor Advisories for CVE-2026-39803 (3)

IV. Related Vulnerabilities

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

V. Comments for CVE-2026-39803

No comments yet

Leave a comment