CVE-2026-27178

HighPublic PoC

Published: 18 February 2026

Published

18 February 2026

Modified

20 February 2026

KEV Added

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Patch

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CVSS Score 7.2 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:N

EPSS Score 0.0004 13.5th percentile

Risk Priority 14 60% EPSS · 20% KEV · 20% CVSS

Summary

CVE-2026-27178 is a high-severity Cross-site Scripting (CWE-79) vulnerability in Mjdm Majordomo. Its CVSS base score is 7.2 (High).

Operationally, exploitation aligns with the MITRE ATT&CK technique Exploit Public-Facing Application (T1190); ranked at the 13.5th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog; a public proof-of-concept is referenced.

Threat & Defense at a Glance

What attackers do: exploitation maps to Exploit Public-Facing Application (T1190) and 2 other techniques.

Threat & Defense Details

Likely Mitigating ControlsAI

Per-CVE control mapping for this CVE has not run yet; the list below is derived from the weakness types (CWEs) cited in the NVD entry.

CA-8 Penetration Testing

addresses: CWE-79

Penetration testing submits XSS payloads to web applications, detecting cross-site scripting flaws for subsequent remediation.

SI-10 Information Input Validation

addresses: CWE-79

Validates web inputs to reject script-related content that could produce XSS.

SI-15 Information Output Filtering

addresses: CWE-79

Output validation against expected content can reject or sanitize script content in generated web pages, reducing XSS exploitability.

MITRE ATT&CK Enterprise TechniquesAI

T1190 Exploit Public-Facing Application Initial Access

Adversaries may attempt to exploit a weakness in an Internet-facing host or system to initially access a network.

attack.mitre.org →

T1185 Browser Session Hijacking Collection

Adversaries may take advantage of security vulnerabilities and inherent functionality in browser software to change content, modify user-behaviors, and intercept information as part of various browser session hijacking techniques.

attack.mitre.org →

T1539 Steal Web Session Cookie Credential Access

An adversary may steal web application or service session cookies and use them to gain access to web applications or Internet services as an authenticated user without needing credentials.

attack.mitre.org →

Why these techniques?

Stored XSS in public-facing web app enables unauthenticated script injection that auto-executes in admin browsers, directly facilitating T1190 (exploit public-facing app), T1185 (browser session hijacking), and T1539 (steal web session cookie via exfiltration).

Confidence: HIGH · MITRE ATT&CK Enterprise v18.1

NVD Description

MajorDoMo (aka Major Domestic Module) contains a stored cross-site scripting (XSS) vulnerability through method parameter injection into the shoutbox. The /objects/?method= endpoint allows unauthenticated execution of stored methods with attacker-controlled parameters. Default methods such as ThisComputer.VolumeLevelChanged pass the user-supplied VALUE…

parameter directly into the say() function, which stores the message raw in the shouts database table without escaping. The shoutbox widget renders stored messages without sanitization in both PHP rendering code and HTML templates. Because the dashboard widget auto-refreshes every 3 seconds, the injected script executes automatically when any administrator loads the dashboard, enabling session hijack through cookie exfiltration.

Deeper analysisAI

CVE-2026-27178 is a stored cross-site scripting (XSS) vulnerability in MajorDoMo (also known as Major Domestic Module), affecting the shoutbox component. The issue stems from method parameter injection at the /objects/?method= endpoint, which permits unauthenticated execution of stored methods using attacker-controlled parameters. Default methods, such as ThisComputer.VolumeLevelChanged, pass the user-supplied VALUE parameter directly into the say() function. This stores the raw message in the shouts database table without escaping, and the shoutbox widget renders these messages without sanitization in both PHP code and HTML templates.

Unauthenticated attackers can exploit the vulnerability by injecting malicious payloads via the endpoint. The shoutbox widget on the dashboard auto-refreshes every 3 seconds, causing the injected script to execute automatically whenever an administrator loads the dashboard. This enables session hijacking through cookie exfiltration. The vulnerability carries a CVSS v3.1 base score of 7.2 (AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:N) and maps to CWE-79.

Advisories recommend applying the patch provided in GitHub pull request #1177 at https://github.com/sergejey/majordomo/pull/1177. Further details on the vulnerability and mitigation are available in the chocapikk blog post at https://chocapikk.com/posts/2026/majordomo-revisited/ and the VulnCheck advisory at https://www.vulncheck.com/advisories/majordomo-stored-cross-site-scripting-via-method-parameters-to-shoutbox.