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Public proof of conceptFix available

CVE-2026-73258

A public proof of concept exists; no exploitation attested.

  • Published2026-08-20
  • Fixed in7.22
  • WeaknessCWE-697

Am I affected?

With a domain, we read the version its public headers and pages expose. A distribution build can carry the fix under an older number.

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.

Timeline

dates in UTC
  1. 2026-08-2018:16CVE publishedNVD

Versions per branch

NVD
Cesanta mongoose
BranchAffectedFixed in
7.22< 7.227.22

as publishedRanges as NVD and OSV publish them; a distribution’s build can be fixed under an older number.

Products declared by the CNA1 product

As GitHub_M, the CNA that assigned this CVE, declared them in the CVE record; versions as written.

  • cesanta mongoose
    Affected
    • = < 7.22no fix stated

Source: the CNA record (CVE Program), © The MITRE Corporation,CVE Terms of UseCVE recordupdated 2026-08-20

Distribution builds and vendor advisories

Packages from OSV.dev and products from the vendors' CSAF advisories.

version not verifiedVersions not verified: read as OSV.dev and the vendors publish them, not checked against each vendor's release list.

Packages

  • mongooseUbuntu:26.10all versions · no fixed version listed
  • mongooseDebian:14all versions · fixed in 7.22+ds-1

Full record on NVD

Fix

  1. Update Cesanta mongoose to 7.22

Advisories and patches

Detection

Nuclei template
none so far
ProjectDiscovery
Exploit-DB
no entry
Exploit-DB
Proof of concept
Metasploit modules
none listed
Metasploit Framework

Sources

  • NVDCVE recordread 2026-10-23
  • CISA-ADPSSVC decisionpoc2026-08-20
  • CNACVSS 3.16.5known since 2026-10-23
  • CNAweakness (CWE)CWE-697known since 2026-10-23
  • FIRST EPSSEPSS score0.5 %2026-11-08
  • OSVaffected packages—

Identifiers

Technical details

CVSS v3 Vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N
Published
2026-08-20
Last Modified
2026-10-18
NVD status
Analyzed

Frequently asked questions

What is CVE-2026-73258?

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.

Is CVE-2026-73258 actively exploited?

A proof-of-concept exploit exists for CVE-2026-73258, but active exploitation has not been confirmed at this time.

What is the CVSS score for CVE-2026-73258?

CVE-2026-73258 has a CVSS v3 base score of 6.5 (MEDIUM severity), with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N.

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