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CVE-2020-35479

MediaWiki before 1.35.1 allows XSS via BlockLogFormatter.php. Language::translateBlockExpiry...

6.1 MediumFix available

MediaWiki before 1.35.1 allows XSS via BlockLogFormatter.php. Language::translateBlockExpiry itself does not escape in all code paths. For example, the return of Language::userTimeAndDate is is always unsafe for HTML in a month value. This affects MediaWiki 1.12.0 and later.

Attack profile

How easy it is to exploit

Attack vector
Network
Complexity
Low
Privileges needed
None
User interaction
Required

What an attacker can affect

Confidentiality
Low
Integrity
Low
Availability
None

Exploit likelihood

1.49%Up 0.2 points since Apr 14, 2021
90%50%10%1%

What each source reports

NVD Score used 6.1

MediaWiki before 1.35.1 allows XSS via BlockLogFormatter.php. Language::translateBlockExpiry itself does not escape in all code paths. For example, the return of Language::userTimeAndDate is is always unsafe for HTML in a month value. This affects MediaWiki 1.12.0 and later.

Record
CVE-2020-35479
CVSS 3.1
6.1 MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
CVSS 2.0
4.3 MediumAV:N/AC:M/Au:N/C:N/I:P/A:N
Weakness
CWE-79
Updated
2026-11-02
CVE List No score

MediaWiki before 1.35.1 allows XSS via BlockLogFormatter.php. Language::translateBlockExpiry itself does not escape in all code paths. For example, the return of Language::userTimeAndDate is is always unsafe for HTML in a month value. This affects MediaWiki 1.12.0 and later.

Record
CVE-2020-35479
Updated
2026-11-02
EUVDEUVD-2020-23150 No score

MediaWiki before 1.35.1 allows XSS via BlockLogFormatter.php. Language::translateBlockExpiry itself does not escape in all code paths. For example, the return of Language::userTimeAndDate is is always unsafe for HTML in a month value. This affects MediaWiki 1.12.0 and later.

Record
EUVD-2020-23150
Updated
2026-11-03
GitHub AdvisoriesGHSA-2m4p-pvg2-r5cw 6.1

MediaWiki before 1.35.1 allows XSS via BlockLogFormatter.php. Language::translateBlockExpiry...

MediaWiki before 1.35.1 allows XSS via BlockLogFormatter.php. Language::translateBlockExpiry itself does not escape in all code paths. For example, the return of Language::userTimeAndDate is is always unsafe for HTML in a month value. This affects MediaWiki 1.12.0 and later.

Record
GHSA-2m4p-pvg2-r5cw
CVSS 3.1
6.1 MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
Weakness
CWE-79
Updated
2026-11-02
OSV 6.1

MediaWiki before 1.35.1 allows XSS via BlockLogFormatter.php. Language::translateBlockExpiry itself does not escape in all code paths. For example, the return of Language::userTimeAndDate is is always unsafe for HTML in a month value. This affects MediaWiki 1.12.0 and later.

Record
CVE-2020-35479
CVSS 3.1
6.1 MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
Updated
2026-11-02
OSVDEBIAN-CVE-2020-35479 6.1

MediaWiki before 1.35.1 allows XSS via BlockLogFormatter.php. Language::translateBlockExpiry itself does not escape in all code paths. For example, the return of Language::userTimeAndDate is is always unsafe for HTML in a month value. This affects MediaWiki 1.12.0 and later.

Record
DEBIAN-CVE-2020-35479
CVSS 3.1
6.1 MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
Updated
2026-11-02
OSVUBUNTU-CVE-2020-35479 6.1

MediaWiki before 1.35.1 allows XSS via BlockLogFormatter.php. Language::translateBlockExpiry itself does not escape in all code paths. For example, the return of Language::userTimeAndDate is is always unsafe for HTML in a month value. This affects MediaWiki 1.12.0 and later.

Record
UBUNTU-CVE-2020-35479
CVSS 3.1
6.1 MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
Updated
2026-11-02
OSVBIT-mediawiki-2020-35479 No score

MediaWiki before 1.35.1 allows XSS via BlockLogFormatter.php. Language::translateBlockExpiry itself does not escape in all code paths. For example, the return of Language::userTimeAndDate is is always unsafe for HTML in a month value. This affects MediaWiki 1.12.0 and later.

Record
BIT-mediawiki-2020-35479
Updated
2026-11-02
OSVMGASA-2021-0086 No score

Updated mediawiki packages fix security vulnerability

In MediaWiki before 1.31.11, the messages userrights-expiry-current and userrights-expiry-none can contain raw HTML. XSS can happen when a user visits Special:UserRights but does not have rights to change all userrights, and the table on the left side has unchangeable groups in it. The right column with the changeable groups is not affected and is escaped correctly (CVE-2020-35475).

MediaWiki before 1.31.11 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 (CVE-2020-35477).

MediaWiki before 1.31.11 allows XSS via BlockLogFormatter.php. Language::translateBlockExpiry itself does not escape in all code paths. For example, the return of Language::userTimeAndDate is always unsafe for HTML in a month value (CVE-2020-35479).

An issue was discovered in MediaWiki before 1.31.11. 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 (CVE-2020-35480).

Record
MGASA-2021-0086
Updated
2026-11-02

Affected products

Affected packages

Affected packages
PackageAffectedFixed
mediawiki
Bitnami
 1.12.0 up to 1.35.1
1.35.1
mediawiki
Debian:12
 before 1:1.35.1-1
1:1.35.1-1
mediawiki
Debian:13
 before 1:1.35.1-1
1:1.35.1-1
mediawiki
Debian:14
 before 1:1.35.1-1
1:1.35.1-1
mediawiki
Debian:9
From an advisory covering 4 CVEs
 before 1:1.27.7-1~deb9u7, plus listed versions
1:1.27.3-11:1.27.4-11:1.27.4-1~bpo8+11:1.27.4-1~deb9u11:1.27.4-2
Show 9 moreShow less
1:1.27.4-31:1.27.5-1~deb9u11:1.27.6-1~deb9u11:1.27.7-1~deb9u11:1.27.7-1~deb9u21:1.27.7-1~deb9u31:1.27.7-1~deb9u41:1.27.7-1~deb9u51:1.27.7-1~deb9u6
1:1.27.7-1~deb9u7
mediawiki
Debian:10
From an advisory covering 4 CVEs
 before 1:1.31.12-1~deb10u1, plus listed versions
1:1.31.10-1~deb10u11:1.31.2-11:1.31.4-11:1.31.4-1~deb10u11:1.31.5-1
Show 7 moreShow less
1:1.31.5-21:1.31.5-31:1.31.6-11:1.31.6-1~deb10u11:1.31.7-11:1.31.7-1~deb10u11:1.31.8-1
1:1.31.12-1~deb10u1
mediawiki
Mageia:7
From an advisory covering 4 CVEs
 before 1.31.12-1.mga7
1.31.12-1.mga7
mediawiki
Ubuntu:18.04:LTS
 All versions, plus listed versions
1:1.27.3-11:1.27.4-11:1.27.4-21:1.27.4-3
 None known
mediawiki
Ubuntu:Pro:20.04:LTS
 All versions, plus listed versions
1:1.31.2-1ubuntu11:1.31.5-11:1.31.5-1ubuntu11:1.31.5-21:1.31.5-3
Show 4 moreShow less
1:1.31.5-3ubuntu11:1.31.6-11:1.31.7-11:1.31.7-1ubuntu0.1~esm1
 None known
mediawiki
Ubuntu:Pro:22.04:LTS
 All versions, plus listed versions
1:1.35.3-11:1.35.4-11:1.35.5-11:1.35.5-1ubuntu11:1.35.5-1ubuntu21:1.35.5-1ubuntu31:1.35.6-11:1.35.6-1ubuntu0.1~esm1
 None known
Show 4 moreShow less
Affected packages
PackageAffectedFixed
mediawiki
Ubuntu:Pro:24.04:LTS
 All versions, plus listed versions
1:1.39.4-21:1.39.5-11:1.39.6-11:1.39.7-11:1.39.7-1ubuntu0.1~esm1
 None known
mediawiki
Ubuntu:25.10
 All versions, plus listed versions
1:1.43.1+dfsg-11:1.43.1+dfsg-21:1.43.3+dfsg-1
 None known
mediawiki
Ubuntu:26.10
 All versions, plus listed versions
1:1.43.8+dfsg-21:1.43.9+dfsg-11:1.43.9+dfsg-1ubuntu1
 None known
mediawiki
Ubuntu:26.04:LTS
 All versions, plus listed versions
1:1.43.3+dfsg-11:1.43.5+dfsg-11:1.43.6+dfsg-21:1.43.8+dfsg-11:1.43.8+dfsg-2
 None known

History

History
RecordedChangedSources
affected, facts
aliasesEUVD
first indexedCVE List, GitHub Advisories, NVD, OSV

Dates are when Every CVE recorded each change. Upstream dates may differ.

In short

CVE-2020-35479 is a medium vulnerability (CVSS 6.1) in Mediawiki, published December 18, 2020. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 1.49%, the 74th percentile. Fixed in mediawiki 1.35.1.

References

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