CVE-2026-39837Public exploitNetwork attack vector

Stored XSS via unreserved dynamic-table attributes

Published Apr 7, 2026 · Updated Apr 7, 2026

Stored XSS in MediaWiki Cargo before 3.8.7 allows remote authenticated users to execute script in viewers' browsers through dynamic tables. Cargo emits attacker-controlled dynamic-table attributes with generic data- names that MediaWiki processes as rich attributes instead of reserving them under data-mw-. Exploitation requires low-privileged page-editing access and a victim to view the affected output; impact remains within the victim's browser context.

CVSS severity6.3
Medium
EPSS probability0.19%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Stored XSS in MediaWiki Cargo before 3.8.7 allows remote authenticated users to execute script in viewers' browsers through dynamic tables. Cargo emits attacker-controlled dynamic-table attributes with generic data- names that MediaWiki processes as rich attributes instead of reserving them under data-mw-. Exploitation requires low-privileged page-editing access and a victim to view the affected output; impact remains within the victim's browser context.

The record

CVE
CVE-2026-39837
Published
Apr 7, 2026
Updated
Apr 7, 2026
Vendor
Wikimedia Foundation
Product
MediaWiki Cargo
Classifications
CWE-80, T1203
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Apr 7, 2026CVE publishedPublication date reported by the CVE source.
  2. Apr 7, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=0 <3.8.7

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Wikimedia Foundation · MediaWiki Cargoversion=0 <3.8.7

Published CVSS scores

5.4NISTCVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N
6.3Wikimedia FoundationCVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:P/VC:N/VI:N/VA:N/SC:H/SI:H/SA:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-80Improper Neutralization of Script-Related HTML Tags in a Web Page (Basic XSS)
T1203Exploitation for Client Execution

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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