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Mongoose CVE-2026-73254

| EUVDEUVD-2026-63496 MEDIUM
Cross-site Scripting (XSS) (CWE-79)
2026-08-20 GitHub_M
5.4
CVSS 3.1 · Vendor: GitHub_M
View

Vulnerability Assessment

Weakness
CWE
OWASP Top 10:2025
A05:2025 - Injection
ASVS 5.0
V1 - Encoding and Sanitization Output encoding, context-aware escaping
MITRE ATT&CK

2 techniques across 2 tactics: Initial Access, Execution

The technique list with ATT&CK links and the kill-chain view is part of the Basic plan and up.

This Month Plan within 30 days. Why: MEDIUM severity (CVSS 4.0-6.9).
Patch available 0.2% exploitation probability (EPSS)

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AnalysisAIv1 – Aug 20, 2026

Stored cross-site scripting in Cesanta Mongoose's directory listing feature allows an attacker with filesystem write access to a served directory to plant a file whose name contains HTML or JavaScript markup; when any user browses that directory, the raw filename is reflected into the HTML page without escaping, executing arbitrary script in the Mongoose origin. All Mongoose versions prior to 7.22 with MG_ENABLE_DIRLIST enabled are affected. No public exploit or CISA KEV listing is confirmed at time of analysis; the vendor-released fix is available in Mongoose 7.22.

Affected VersionsENISA

Mongoose < 7.22

Affected Packages

euvd mongoose fix: 7.22

Source: OSV (Open Source Vulnerabilities)

Affects your stack

Affects 1 package in euvd

Checking this CVE against your own stacks and servers is part of the Basic plan and up.

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  • Exploit and PoC references, threat intelligence from 22 sources

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Severity by source

Vendor (GitHub_M) PRIMARY 5.4 MEDIUM
AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:N

Primary rating from Vendor (GitHub_M) · only source for this CVE.

CVSS VectorVendor: GitHub_M

Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
Required
Scope
Unchanged
Confidentiality
Low
Integrity
Low
Availability
None

Lifecycle Timeline

1
Patch available
Aug 20, 2026 - 18:03 EUVD

DescriptionCVE.org

Mongoose is an embedded web server and network library. Prior to 7.22, an attacker who can create a file with an HTML payload in its name can trigger stored cross-site scripting when a user browses a directory served with MG_ENABLE_DIRLIST. The printdirentry() path called by listdir() in src/http.c URL-encodes the href but inserts the raw filesystem filename into the HTML link text. The browser executes the injected markup in the Mongoose origin, which can expose session data or permit actions as the victim. This issue is fixed in version 7.22.

Threat Intelligence Overview

EPSS Score
0.2%
Top 91% exploitable
Data Quality
6 sources
Confidence: High

How this decision was reached

The engine reads each signal below and applies a fixed list of rules from top to bottom. The first rule that matches sets the recommended action – like a statement, every line is shown.

SignalValue
Severity MEDIUM
CISA KEV No
Public POC No
EPSS 0.2%
Patch available Yes
Active threat No
Deciding rule
MEDIUM severity (CVSS 4.0-6.9)
What every action level means
Emergency Immediate action required. Criteria: CRITICAL + in CISA KEV (actively exploited) without patch, OR CRITICAL + EPSS > 30% without patch, OR CRITICAL + active threat signals without patch.
Act Now Prioritize within 24-48h. Criteria: in KEV with patch available, OR CRITICAL + public POC, OR HIGH + EPSS > 10%, OR CRITICAL + active threat, OR any CRITICAL severity.
This Week Schedule remediation this week. Criteria: HIGH severity (CVSS 7.0-8.9). Patch within normal change window.
This Month Plan within 30 days. Criteria: MEDIUM severity (CVSS 4.0-6.9), lower exploitation probability. Include in regular patch cycle.
Monitor Track and reassess. Criteria: LOW severity (CVSS 0.1-3.9), minimal exploitation risk. No immediate action needed.

SSVC AssessmentENISA

SSVC Decision· derived
Scheduled
Exploitation
Poc
System Exposure· derived
Open
Automatable
No
Human Impact· derived
Medium
Technical Impact
Partial

Priority Score

27
Low Medium High Critical
KEV: 0
EPSS: 0
CVSS: +27
PoC: 0
Weaponized: 0
Threat intel: 0
Gov advisory: 0

Attack Technique

Cross-Site Scripting occurs when an application accepts untrusted data and sends it to a web browser without proper validation or encoding.

CVE-2025-23061 CRITICAL POC
9.0 Jan 15

Mongoose ODM for Node.js before version 8.9.5 contains a search injection vulnerability when using $where filters with p

CVE-2017-2894 CRITICAL POC
9.8 Nov 07

An exploitable stack buffer overflow vulnerability exists in the MQTT packet parsing functionality of Cesanta Mongoose 6

CVE-2017-2891 CRITICAL POC
9.8 Nov 07

An exploitable use-after-free vulnerability exists in the HTTP server implementation of Cesanta Mongoose 6.8. Rated crit

CVE-2017-2922 CRITICAL POC
9.8 Nov 07

An exploitable memory corruption vulnerability exists in the Websocket protocol implementation of Cesanta Mongoose 6.8.

CVE-2017-2921 CRITICAL POC
9.8 Nov 07

An exploitable memory corruption vulnerability exists in the Websocket protocol implementation of Cesanta Mongoose 6.8.

CVE-2023-3696 CRITICAL POC
9.8 Jul 17

Prototype Pollution in GitHub repository automattic/mongoose prior to 7.3.4. Rated critical severity (CVSS 9.8), this vu

CVE-2022-2564 CRITICAL POC
9.8 Jul 28

Prototype Pollution in GitHub repository automattic/mongoose prior to 6.4.6. Rated critical severity (CVSS 9.8), this vu

CVE-2019-19307 CRITICAL POC
9.8 Nov 26

An integer overflow in parse_mqtt in mongoose.c in Cesanta Mongoose 6.16 allows an attacker to achieve remote DoS (infin

CVE-2024-53900 CRITICAL POC
9.1 Dec 02

Mongoose before 8.8.3 can improperly use $where in match, leading to search injection. Rated critical severity (CVSS 9.1

CVE-2021-26530 CRITICAL POC
9.1 Feb 08

The mg_tls_init function in Cesanta Mongoose HTTPS server 7.0 (compiled with OpenSSL support) is vulnerable to remote OO

CVE-2021-26529 CRITICAL POC
9.1 Feb 08

The mg_tls_init function in Cesanta Mongoose HTTPS server 7.0 and 6.7-6.18 (compiled with mbedTLS support) is vulnerable

CVE-2021-26528 CRITICAL POC
9.1 Feb 08

The mg_http_serve_file function in Cesanta Mongoose HTTP server 7.0 is vulnerable to remote OOB write attack via connect

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