CVE-2026-73259

Mongoose: Reflected XSS via decoded URI in directory listing render

MEDIUM
5.4
CVSS Score
Published: August 20, 2026 at 05:39 PM UTC
Updated: October 18, 2026 at 08:10 PM UTC
1 product affected across 1 vendorMongoose

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Severity
MEDIUM5.4
Exploit prediction
EPSS 0.4%
SSVC
PoC

Description

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 session data or perform actions as the victim. This issue is fixed in version 7.22.

Affected

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

v < 7.22
Affected range stops below 7.22, so it looks safe — our inference, not a vendor statement

Remediation

No guide yet

No remediation guidance has been written for this CVE yet. What the record does show:

References (4)

x_refsource_CONFIRMExploitVendor Advisory
Source: cverecord
https://github.com/cesanta/mongoose/security/advisories/GHSA-9cwm-487w-h25w
x_refsource_MISCIssue TrackingPatch
Source: cverecord
https://github.com/cesanta/mongoose/pull/3611
x_refsource_MISCRelease Notes
Source: cverecord
https://github.com/cesanta/mongoose/releases/tag/7.22

SSVC — Action Prioritization

SSVCPoCNot automatablePartial impact

SSVC signals action urgency (what to patch first), separate from CVSS which measures severity.

CVSS

5.4MEDIUMGitHub_M
Attack Vector
NETWORK
Complexity
LOW
Privileges
NONE
User Interaction
REQUIRED
Scope
UNCHANGED
Confidentiality
LOW
Integrity
LOW
Availability
NONE
Vector?

Quick Info

StatusANALYZED
CWE
CWE-79

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