CVE-2026-54221 Reflected XSS in UBB.threads
Attackers can execute arbitrary JavaScript in victims' browsers via crafted links in UBB.threads, potentially leading to session hijacking or data theft.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- A user has to click or open something
- Fix
- None listed
What is CVE-2026-54221?
CVE-2026-54221 is a medium-severity cross-site scripting vulnerability in UBB.threads, published on 18 Jun 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Official description
UBB.threads is vulnerable to Reflected XSS. The application improperly handles user input in certain requests, enabling attackers to execute arbitrary JavaScript in the context of a victim's browser by tricking them into clicking a crafted link. Because vendor contact attempts were unsuccessful, the vulnerability has only been confirmed in version 7.7.5 but may also affect other versions.
Weakness: CWE-79
Which versions are affected by CVE-2026-54221?
How do I fix CVE-2026-54221?
No fix has been published for CVE-2026-54221 yet. Limit exposure of the affected software until one is available.
Escape output for the context it lands in and set a strict Content Security Policy. Upgrading the affected component is the real fix. More about Cross-site scripting.
Is CVE-2026-54221 being exploited?
There is no known exploitation of CVE-2026-54221 in the wild and no public exploit code.
Sources
Also known as GHSA-9c46-2jjw-rj67.