CVE-2026-0817: Missing Authorization vulnerability in Wikimedia Foundation MediaWiki - CampaignEvents extension allows Privil

Routine

MEDIUM 5.3REMOTEDOWNGRADE

CVE-2026-0817 is a medium-severity flaw (CVSS 5.3) affecting campaignevents. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Missing Authorization vulnerability in Wikimedia Foundation MediaWiki - CampaignEvents extension allows Privilege Abuse.This issue affects MediaWiki - CampaignEvents extension: 1.45, 1.44, 1.43, 1.39.

Why this priority

Remotely exploitable, no login, no user action

No fix is published yet: follow the downgrade or mitigation steps.

Risk facts

CVSS score	5.3 (Medium)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	0.3% (top 81%)
CISA exploited list	No
Weakness	CWE-862
Published	2026-01-09
Last modified	2026-06-17

Publisher (CNA): wikimedia-foundation · Vendor: wikimedia

Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-01-09 16:16 UTCPublished CVE record published
2026-06-17 10:11 UTCUpdated Record last modified

wikimedia campaignevents DOWNGRADE

Affected: 1.39 · 1.43 · 1.44 · 1.45

Fixed in: no fixed release known

Safe to downgrade to: a release before 1.39

1. Check installed version

apt-cache policy campaignevents || rpm -q campaignevents || campaignevents --version

2. No fixed release: DOWNGRADE to a release before 1.39 (Debian / Ubuntu)

apt-cache madison campaignevents sudo apt install campaignevents=<VERSION_BEFORE_1.39> sudo apt-mark hold campaignevents

2. No fixed release: DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list campaignevents sudo dnf downgrade campaignevents-<VERSION_BEFORE_1.39> sudo dnf versionlock add campaignevents

Downgrade risk

Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.

After downgrade

Restart the service, and keep the package held until a fixed release ships.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2026-0817?

campaignevents: downgrade or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2026-0817 being exploited?

CVE-2026-0817 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2026-0817 affect?

CVE-2026-0817 affects campaignevents. Severity is medium (CVSS 5.3). Missing Authorization vulnerability in Wikimedia Foundation MediaWiki - CampaignEvents extension allows Privilege Abuse.This issue affects MediaWiki - CampaignEvents extension: 1.45, 1.44, 1.43, 1.39.

How urgent is CVE-2026-0817?

Priority 28/100. Remotely exploitable, no login, no user action

Related CVEs

CVE-2025-53490 MEDIUM 5.6 MITIGATE Improper Neutralization of Input During Web Page Generation (XSS or 'Cross-site Scripting') vulnerability in W

References

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