CVE-2020-35480

Severity: medium (CVSS 5.3 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 1.5% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2020-12-18 · updated 2026-06-17
Weakness: CWE-203

Description

An issue was discovered in MediaWiki before 1.35.1. Missing users (accounts that don't exist) and hidden users (accounts that have been explicitly hidden due to being abusive, or similar) that the viewer cannot see are handled differently, exposing sensitive information about the hidden status to unprivileged viewers. This exists on various code paths.

Affected products

Debian Linux: 9.0, 10.0
Fedoraproject Fedora: 33
Wikimedia Foundation MediaWiki: before 1.35.1 — fixed in 1.35.1

How to fix

Upgrade to a fixed version: Wikimedia Foundation MediaWiki 1.35.1. Check the vendor advisory for mitigations.

References

https://lists.debian.org/debian-lts-announce/2020/12/msg00034.html
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/STT5Z4A3BCXVH3WIPICWU2FP4IPIMUPC/
https://lists.wikimedia.org/pipermail/mediawiki-announce/2020-December/000268.html
https://phabricator.wikimedia.org/T120883
https://www.debian.org/security/2020/dsa-4816
https://lists.debian.org/debian-lts-announce/2020/12/msg00034.html
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/STT5Z4A3BCXVH3WIPICWU2FP4IPIMUPC/
https://lists.wikimedia.org/pipermail/mediawiki-announce/2020-December/000268.html
https://phabricator.wikimedia.org/T120883
https://www.debian.org/security/2020/dsa-4816

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