VulnerabilityPublished 7 Jan 2026

CVE-2026-0669: Wikimedia Foundation MediaWiki – CSS extension · Path Traversal

Affects Wikimedia Foundation MediaWiki – CSS extensionSource CVE Database V5

Not known to be exploited · CVSS 7.5 High.

Data as of 26 Oct 2026, 17:16 UTC

CVSS 3.1 base score

7.5High

How severe the flaw is on the 0–10 CVSS scale.

EPSS: 0.4% chance of exploitation in 30 days – higher than 38% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

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

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Network: The vulnerable component is bound to the network stack and the set of possible attackers extends beyond the other options listed, up to and including the entire Internet. Such a vulnerability is often termed 'remotely exploitable' and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers).
Attack Complexity: Low: Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success against the vulnerable component.
Privileges Required: None: The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files to carry out an attack.
User Interaction: None: The vulnerable system can be exploited without any interaction from any user.
Scope: Unchanged: An exploited vulnerability can only affect resources managed by the same security authority. In this case, the vulnerable component and the impacted component are either the same, or both are managed by the same security authority.
Confidentiality: High: There is total loss of confidentiality, resulting in all resources within the impacted component being divulged to the attacker. Alternatively, access to only some restricted information is obtained, but the disclosed information presents a direct, serious impact.
Integrity: None: There is no loss of integrity within the impacted component.
Availability: None: There is no impact to availability within the impacted component.

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 7 Jan 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponised: Public exploit code exists in Metasploit or Exploit-DB, or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Affected software

Product	Affected	Fixed in
Wikimedia FoundationMediaWiki - CSS extension	Affected =1.44 =1.43 =1.39	Fixed in–

AI-suggested

Monitor Wikimedia Foundation advisories closely and apply official patches for the CSS extension as soon as they are released.
Until patches are available, implement strict input validation and sanitization on all file path parameters handled by the CSS extension to prevent directory traversal sequences (e.g., '../').
Restrict file system permissions for the MediaWiki server process to limit access only to necessary directories and files, minimizing exposure if traversal occurs.
Employ web application firewalls (WAFs) with rules designed to detect and block path traversal attack patterns targeting MediaWiki endpoints.
Conduct regular security audits and penetration testing focusing on MediaWiki installations to identify and remediate similar vulnerabilities.
Educate administrators and developers about secure coding practices related to file handling and path validation.
Consider isolating MediaWiki instances in segmented network zones to reduce potential lateral movement if compromised.
Maintain comprehensive logging and monitoring to detect suspicious access attempts indicative of exploitation attempts.

Description

CVE-2026-0669 is a high-severity path traversal vulnerability in the CSS extension of Wikimedia Foundation's MediaWiki versions 1.39, 1.43, and 1.44. This flaw allows an unauthenticated remote attacker to read arbitrary files on the server by manipulating file path inputs, bypassing directory restrictions. The vulnerability impacts confidentiality but does not affect integrity or availability. No user interaction or privileges are required for exploitation, and no known exploits are currently reported in the wild. European organizations using affected MediaWiki versions, especially those hosting sensitive or proprietary information, face significant data exposure risks. Mitigation requires promptly updating to patched versions once available or applying strict input validation and access controls on the CSS extension. Countries with high MediaWiki adoption in government, education, and public sectors—such as Germany, France, the UK, and the Netherlands—are most at risk.

Impact

For European organizations, the primary impact of CVE-2026-0669 is unauthorized disclosure of sensitive information stored on MediaWiki servers. This could include internal documentation, user data, or proprietary content, leading to confidentiality breaches. Organizations in sectors like government, education, and research that rely on MediaWiki for knowledge management are especially vulnerable. Exposure of sensitive files could result in reputational damage, regulatory penalties under GDPR for data leaks, and potential exploitation of disclosed information for further attacks. Since the vulnerability does not affect integrity or availability, the risk is focused on data confidentiality. The ease of exploitation without authentication increases the threat level, potentially enabling widespread scanning and data theft across European networks. The absence of known exploits currently provides a window for proactive defense, but the risk of future exploitation remains high.

Summary

CVE-2026-0669 identifies a path traversal vulnerability (CWE-22) in the CSS extension of the MediaWiki platform maintained by the Wikimedia Foundation. The affected versions are 1.39, 1.43, and 1.44. This vulnerability arises due to improper limitation of pathname inputs, allowing attackers to craft requests that traverse directories outside the intended restricted folder. As a result, an attacker can access arbitrary files on the server hosting MediaWiki without authentication or user interaction. The vulnerability impacts confidentiality by exposing potentially sensitive files but does not compromise data integrity or system availability. The CVSS 3.1 base score is 7.5, reflecting network attack vector, low attack complexity, no privileges required, no user interaction, and high confidentiality impact. Although no public exploits are currently known, the straightforward nature of path traversal attacks makes this a significant risk. MediaWiki is widely used in various organizations, including governmental and educational institutions, making this vulnerability particularly concerning for entities managing sensitive content. The lack of available patches at the time of reporting necessitates immediate interim mitigations such as input validation and access control enforcement on the CSS extension component.

CWE-22Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal') (opens in a new tab)
Base weaknessLikelihood of exploit: HighCWE Top 25 (2025): #6OWASP Top 10 A01:2025: Broken Access Control (opens in a new tab)
The product uses external input to construct a pathname that is intended to identify a file or directory that is located underneath a restricted parent directory, but the product does not properly neutralize special elements within the pathname that can cause the pathname to resolve to a location that is outside of the restricted directory.
Implementation · Input Validation
Assume all input is malicious. Use an "accept known good" input validation strategy, i.e., use a list of acceptable inputs that strictly conform to specifications. Reject any input that does not strictly conform to specifications, or transform it into something that does.
Architecture and Design
For any security checks that are performed on the client side, ensure that these checks are duplicated on the server side, in order to avoid CWE-602. Attackers can bypass the client-side checks by modifying values after the checks have been performed, or by changing the client to remove the client-side checks…
Implementation · Input Validation
Inputs should be decoded and canonicalized to the application's current internal representation before being validated (CWE-180). Make sure that the application does not decode the same input twice (CWE-174).
OWASP Cheat Sheets
Authorization (opens in a new tab)
OWASP ASVS 4.0.3
V12.3.1 (opens in a new tab)
Attack patterns
Path Traversal (opens in a new tab)
Using Slashes and URL Encoding Combined to Bypass Validation Logic (opens in a new tab)
Manipulating Web Input to File System Calls (opens in a new tab)
Using Escaped Slashes in Alternate Encoding (opens in a new tab)
Using Slashes in Alternate Encoding (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

References

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 14 Jan 2026, 19:45 UTC

WeaknessesCWE-22

Technical details

References

Community reviews

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