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

Goal: 1000 CNY · Raised: 1336 CNY

100%
Buy Us a Coffee

CVE-2026-73256— Mongoose: HTTP/1.0 detection off-by-one enables request smuggling via chunked TE

Quick assessment

Affected
cesanta mongoose
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.

Mongoose 是一个嵌入式 Web 服务器和网络库。在版本 7.22 之前，远程未授权攻击者可以通过发送具有 头部且帧结构冲突的 HTTP/1.0 请求，来利用基于反向代理的部署场景。 中的 函数使用一个不可能成立的“大于八字节”条件对 进行检查，而 实际要求协议字符串长度为八字节，这导致 标志始终无法被设置为真。因此，Mongoose 会处理那些 HTTP/1.0 代理通常应忽略的块编码（chunked encoding），从而引发请求走私（request smuggling），并可能导致未授权访问或状态篡改

CVSS 9.1 · Critical EPSS 0.40% · P33

Affected Version Matrix 1

VendorProduct Version RangeStatus
cesanta mongoose < 7.22 affected
Get alerts for future matching vulnerabilities Log in to subscribe

I. Basic Information for CVE-2026-73256

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Although we use advanced large model technology, its output may still contain inaccurate or outdated information.Shenlong tries to ensure data accuracy, but please verify and judge based on the actual situation.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
Mongoose: HTTP/1.0 detection off-by-one enables request smuggling via chunked TE
Source: CVE Program / CVE List V5
Vulnerability Description
Mongoose is an embedded web server and network library. Prior to 7.22, a remote unauthenticated attacker can exploit an HTTP/1.0 reverse-proxy deployment by sending a request with Transfer-Encoding: chunked and conflicting framing. The http_cb() function in src/http.c tests hm.proto.len with an impossible greater-than-eight condition even though mg_http_parse() requires an eight-byte protocol string, so is_http_1_0 is never set. Mongoose consequently processes chunked encoding that an HTTP/1.0 proxy can ignore, enabling request smuggling and unauthorized access or state changes. This issue is fixed in version 7.22.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
Source: CVE Program / CVE List V5
Vulnerability Type
HTTP请求的解释不一致性(HTTP请求私运)
Source: CVE Program / CVE List V5

Affected Products

Vendor Product Affected Versions CPE Subscribe
cesanta mongoose < 7.22 -

II. Public POCs for CVE-2026-73256

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

No public POC found.

Login to generate AI POC

III. Intelligence Information for CVE-2026-73256

请登录查看更多情报信息。

Patches & Fixes for CVE-2026-73256 (1)

Vendor Advisories for CVE-2026-73256 (1)

Vendor Pages for CVE-2026-73256 (1)

Same Patch Batch · cesanta · 2026-08-20 · 8 CVEs total

CVE-2026-73251 9.3 CRITICAL Mongoose Built-in TLS: CA-bundle certificate chain accepted without any signature verifica
CVE-2026-73257 9.1 CRITICAL Mongoose: Content-Length + Transfer-Encoding coexistence enables request smuggling
CVE-2026-73253 9.1 CRITICAL Mongoose: TLS Hostname Verification Bypass via Overly Permissive Wildcard Matching
CVE-2026-73258 6.5 MEDIUM Mongoose: Multipart boundary/header scan logic error in mg_http_next_multipart
CVE-2026-73255 6.5 MEDIUM Mongoose: Path traversal in SSI #include directives enables arbitrary file read
CVE-2026-73254 5.4 MEDIUM Mongoose: Stored XSS via unescaped filenames in directory listing
CVE-2026-73259 5.4 MEDIUM Mongoose: Reflected XSS via decoded URI in directory listing render

IV. Related Vulnerabilities

Same product: mongoose
Same vendor: cesanta
Same weakness: CWE-444

V. Comments for CVE-2026-73256

No comments yet

Leave a comment