CVE-2026-73259: Mongoose is an embedded web server and network library

Q: How do I fix CVE-2026-73259?

mongoose: upgrade to 7.22. Exact commands for each OS are on this page.

Q: Is CVE-2026-73259 being exploited?

CVE-2026-73259 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2026-73259 affect?

CVE-2026-73259 affects mongoose. Severity is medium (CVSS 5.4). Mongoose is an embedded web server and network library. Prior to 7.22, a remote attacker can send a crafted percent-encoded request path to a deployment using MG_ENABLE_DIRLIST and persuade a user to visit it. The mg_http_serve_dir() and li

Q: How urgent is CVE-2026-73259?

Priority 33/100. Public exploit reference

Routine

MEDIUM 5.4UPGRADE

CVE-2026-73259 is a medium-severity flaw (CVSS 5.4) affecting mongoose. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Mongoose is an embedded web server and network library. Prior to 7.22, a remote attacker can send a crafted percent-encoded request path to a deployment using MG_ENABLE_DIRLIST and persuade a user to visit it. The mg_http_serve_dir() and listdir() path in src/http.c places the decoded request URI into the title and h1 elements without HTML entity encoding. The resulting reflected cross-site scripting executes in the Mongoose origin and can expose

Why this priority

Public exploit reference

A fixed release or distro patch exists.

Risk facts

CVSS score	5.4 (Medium)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	Required
EPSS exploit chance	0.4% (top 65%)
CISA exploited list	No
Weakness	CWE-79
Published	2026-08-20
Last modified	2026-10-18

Publisher (CNA): GitHub, Inc. · Vendor: cesanta

Last updated 2026-10-18 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-08-20 18:16 UTCPublished CVE record published
2026-10-18 20:10 UTCUpdated Record last modified

cesanta mongoose UPGRADE

Affected: < 7.22

Fixed in: 7.22

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy mongoose || rpm -q mongoose || mongoose --version

2. UPGRADE to 7.22 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade mongoose

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade mongoose

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2026-73259?

mongoose: upgrade to 7.22. Exact commands for each OS are on this page.

Is CVE-2026-73259 being exploited?

CVE-2026-73259 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2026-73259 affect?

CVE-2026-73259 affects mongoose. Severity is medium (CVSS 5.4). Mongoose is an embedded web server and network library. Prior to 7.22, a remote attacker can send a crafted percent-encoded request path to a deployment using MG_ENABLE_DIRLIST and persuade a user to visit it. The mg_http_serve_dir() and li

How urgent is CVE-2026-73259?

Priority 33/100. Public exploit reference

Related CVEs

CVE-2026-5244 HIGH 7.3 UPGRADE A vulnerability has been found in Cesanta Mongoose up to 7.20
CVE-2026-6985 MEDIUM 5.3 UPGRADE A weakness has been identified in Cesanta Mongoose up to 7.20
CVE-2026-5246 MEDIUM 5.6 UPGRADE A vulnerability was determined in Cesanta Mongoose up to 7.20
CVE-2026-5245 MEDIUM 5.6 UPGRADE A vulnerability was found in Cesanta Mongoose up to 7.20
CVE-2026-6986 LOW 3.7 UPGRADE A security vulnerability has been detected in Cesanta Mongoose up to 7.20

References

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