CVE-2026-73256Mongoose: HTTP/1.0 detection off-by-one enables request smuggling via chunked TE
Updated under an hour ago ()
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No exploitation reported and no EPSS estimate yet.
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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.
- CVSS
- 9.1 CRITICAL (v3.1, CNA)CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
- Weakness (CWE)
- CWE-444
- Known exploited
- Not in CISA's KEV catalog
- EPSS (exploitation in the next 30 days)
- Not loaded for this CVE
- Assigned by
- GitHub_M
- NVD analysis
- Analyzed
- Record last updated
- Aug 21, 2026
- First seen by InfoSec Signals
- Oct 9, 2026
Affected products
cesanta mongoose cesanta:mongoose (from the name) | before 7.22 | CNA record |
cesanta mongoose cesanta:mongoose | before 7.22 | NVD |
References
- https://github.com/cesanta/mongoose/security/advisories/GHSA-mgp5-rjrv-h5j3x-refsource-confirm, exploit, vendor-advisory
- https://github.com/cesanta/mongoose/pull/3611x-refsource-misc, issue-tracking, patch
- https://github.com/cesanta/mongoose/commit/a9df523f76f43a38bd53b4232b9cfd4c16869e71x-refsource-misc, patch
- https://github.com/cesanta/mongoose/releases/tag/7.22x-refsource-misc, release-notes
The CVE record on cve.org NVD's entry
The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.