CVE-2026-35054: XenForo before 2.3.9 is vulnerable to stored cross-site scripting (XSS) related to BB code rendering

Q: How do I fix CVE-2026-35054?

xenforo: upgrade to 2.3.9. Exact commands for each OS are on this page.

Q: Is CVE-2026-35054 being exploited?

CVE-2026-35054 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2026-35054 affect?

CVE-2026-35054 affects xenforo. Severity is medium (CVSS 6.4). XenForo before 2.3.9 is vulnerable to stored cross-site scripting (XSS) related to BB code rendering. An attacker can inject malicious scripts through BB code that are stored and executed when other users view the content.

Q: How urgent is CVE-2026-35054?

Priority 23/100. No elevated risk signals yet.

Routine

MEDIUM 6.4UPGRADE

CVE-2026-35054 is a medium-severity flaw (CVSS 6.4) affecting xenforo. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

XenForo before 2.3.9 is vulnerable to stored cross-site scripting (XSS) related to BB code rendering. An attacker can inject malicious scripts through BB code that are stored and executed when other users view the content.

Why this priority

No elevated risk signals yet

A fixed release or distro patch exists.

Risk facts

CVSS score	6.4 (Medium)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	Low
User interaction	None
EPSS exploit chance	0.1% (top 97%)
CISA exploited list	No
Weakness	CWE-79
Published	2026-04-01
Last modified	2026-06-17

Publisher (CNA): VulnCheck · Vendor: xenforo

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

Am I affected?

Timeline

2026-04-01 01:16 UTCPublished CVE record published
2026-06-17 10:40 UTCUpdated Record last modified

xenforo xenforo UPGRADE

Affected: < 2.3.9

Fixed in: 2.3.9

Safe to downgrade to: no unaffected older release

1. Check installed version

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

2. UPGRADE to 2.3.9 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade xenforo

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade xenforo

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

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-2026-35054?

xenforo: upgrade to 2.3.9. Exact commands for each OS are on this page.

Is CVE-2026-35054 being exploited?

CVE-2026-35054 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-2026-35054 affect?

CVE-2026-35054 affects xenforo. Severity is medium (CVSS 6.4). XenForo before 2.3.9 is vulnerable to stored cross-site scripting (XSS) related to BB code rendering. An attacker can inject malicious scripts through BB code that are stored and executed when other users view the content.

How urgent is CVE-2026-35054?

Priority 23/100. No elevated risk signals yet.

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References

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