Reference page — cumulative record through Saturday, October 3, 2026 UTC. Reference pages update as the archive grows; only dated daily editions are immutable pages of record.

CVE-2026-73258

CVE-2026-73258MEDIUM

cesanta mongoose — Mongoose: Multipart boundary/header scan logic error in mg_http_next_multipart

  AV  AC  PR  UI  S  C  I  A   CVSS    EPSS   %ile   KEV
   N   L   N   N  U  L  L  N    6.5   .0046   37.5     —

AFFECTED
  Product   Versions  Fixed
  mongoose  < 7.22 –  —

TIMELINE
  Aug 11  Reserved by GitHub_M
  Aug 20  Published (CNA: GitHub_M)
  Sep 29  EXPLOIT PUBLISHED — CVE-2026-73258 (cesanta mongoose). Public exploit reference added.

CWE-697 · CNA: GitHub_M · CVSS v3.1 · 4 references · NVD status: Analyzed

Description

Mongoose is an embedded web server and network library. Prior to 7.22, a remote attacker can place a lone carriage return or line feed in multipart input processed by mg_http_next_multipart() in src/http.c. The loops comparing s[b] and s[b + 1], and s[h2] and s[h2 + 1], use an incorrect AND condition and stop when either character resembles part of a CRLF terminator. This truncates headers, filenames, or boundaries and can cause an application to accept dangerous content after seeing a misleading Content-Type value. This issue is fixed in version 7.22.

Lifecycle

Complete event history — 3 events, chronological
Date	Event	Detail
August 11, 2026	Reserved	Reserved by GitHub_M
August 20, 2026	Published	Published (CNA: GitHub_M)
September 29, 2026	EXPLOIT PUBLISHED	EXPLOIT PUBLISHED — CVE-2026-73258 (cesanta mongoose). Public exploit reference added.

Affected

Affected products and packages — 1 row
Vendor	Product / Package	Ecosystem	Version introduced	Fixed
cesanta	mongoose	—	< 7.22	—

Weaknesses

CWE-697

References (4)

https://github.com/cesanta/mongoose/commit/a9df523f76f43a38bd53b4232b9cfd4c16869e71 [Patch]
https://github.com/cesanta/mongoose/pull/3611 [Issue Tracking, Patch]
https://github.com/cesanta/mongoose/releases/tag/7.22 [Release Notes]
https://github.com/cesanta/mongoose/security/advisories/GHSA-cc55-8v3r-59p8 [Exploit, Vendor Advisory]

Authoritative record: CVE-2026-73258 at cve.org

Vendors: cesanta

Weaknesses: CWE-697

About this page

This is a reference page, not a dated page of record. It assembles the complete lifecycle of CVE-2026-73258 from the CVE Program record, NVD enrichment, the CISA KEV catalog, EPSS, and OSV advisories. The box score's numbers (CVSS, EPSS, KEV status) are current as of Saturday, October 3, 2026 UTC and are re-derived as the archive grows; only dated daily editions are immutable pages of record. The authoritative source for this identifier is cve.org.