CVE-2026-55850 Element Web: A malicious homeserver can inject HTML in Element Web using its homepage
A malicious homeserver can inject phishing HTML into Element Web's homepage, bypassing content security policies to deceive users.
- 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-2026-55850?
CVE-2026-55850 is a medium-severity cross-site scripting vulnerability in element-hq element-web, published on 21 Aug 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
Element Web is a Matrix web client built using the Matrix React SDK. Prior to 1.12.22, EmbeddedPage in apps/web/src/components/structures/EmbeddedPage.tsx renders homeserver-supplied homepage content through dangerouslySetInnerHTML without passing it through sanitizedHtmlNode. A malicious homeserver can provide crafted HTML that Element Web renders on the homepage; the content security policy prevents JavaScript but not phishing HTML. This issue is fixed in version 1.12.22.
Weakness: CWE-79
Which versions are affected by CVE-2026-55850?
How do I fix CVE-2026-55850?
No fix has been published for CVE-2026-55850 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-2026-55850 being exploited?
There is no known exploitation of CVE-2026-55850 in the wild and no public exploit code.
Sources
Also known as GHSA-wrcp-5v3v-3j6v.