MediaWiki before 1.35.1 blocks legitimate attempts to hide log entries in some situations.

published 2020-12-18 5 y ago modified 2026-06-17 4 mo ago also BIT-mediawiki-2020-35477 , EUVD-2020-23148

cvss: 5.3; version 3.1, NVD
cisa kev: Not listed; not in CISA's catalog
epss: 1.7%; EPSS 1.7% chance of exploitation in 30 days, percentile 77%
public exploits: 0; none known

MediaWiki before 1.35.1 blocks legitimate attempts to hide log entries in some situations. If one sets MediaWiki:Mainpage to Special:MyLanguage/Main Page, visits a log entry on Special:Log, and toggles the "Change visibility of selected log entries" checkbox (or a tags checkbox) next to it, there is a redirection to the main page's action=historysubmit (instead of the desired behavior in which a revision-deletion form appears).

Patch / fix

fixed in 2 distros 2

bitnami mediawiki 1.35.1
mediawiki mediawiki 1.35.1

debian arch linux

mediawiki Debian 14, Debian 13, Debian 12 1:1.35.1-1

debian advisories DEBIAN-CVE-2020-35477

mediawiki Arch Linux 1.35.1-1

arch linux advisories AVG-1371

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2020-35477 updated 2025-11-21 cvss 5.3

mediawiki: unable to change visibility of log entries when MediaWiki:Mainpage uses Special:MyLanguage

Red Hat OpenShift Container Platform 3.11 mediawiki
affected: no fix available “Fix deferred”
Red Hat OpenShift Container Platform 4 mediawiki
affected: no fix planned “Out of support scope”

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

Exploit prediction

1.71% chance of exploitation in the next 30 days, higher than 77% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

phabricator.wikimedia.org https://phabricator.wikimedia.org/T205908 referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by	version	score	vector
NVD	3.1	5.3	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N
NVD	2.0	5.0	AV:N/AC:L/Au:N/C:N/I:P/A:N
OSV	3.1	5.3	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N

Affected packages

ecosystem	package	affected	fixed in
bitnami	mediawiki	<1.35.1	1.35.1

Classification

Weakness

CWE-670 Always-Incorrect Control Flow Implementation

References

phabricator.wikimedia.org /T205908
exploit, issue-tracking, third-party-advisory, web
debian.org /security/2020/dsa-4816
vendor-advisory, third-party-advisory, web
lists.fedoraproject.org /archives/list/package-announce%40lists.fedoraproject.org/message/STT5Z4A3BCXVH3WIPICWU2FP4IPIMUPC/
vendor-advisory, web
lists.wikimedia.org /pipermail/mediawiki-announce/2020-December/000268.html
mailing-list, release-notes, vendor-advisory, web
lists.debian.org /debian-lts-announce/2020/12/msg00034.html
mailing-list, third-party-advisory, web
nvd.nist.gov /vuln/detail/CVE-2020-35477
web

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

Summary