CVE-2020-26956 Cross-site scripting in Firefox
Attackers can execute arbitrary scripts via SVG event handlers retained during HTML sanitization in Firefox and Thunderbird.
- 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
- Available
What is CVE-2020-26956?
CVE-2020-26956 is a medium-severity cross-site scripting vulnerability in Mozilla Firefox, published on 9 Dec 2020. 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
In some cases, removing HTML elements during sanitization would keep existing SVG event handlers and therefore lead to XSS. This vulnerability affects Firefox < 83, Firefox ESR < 78.5, and Thunderbird < 78.5.
Weakness: CWE-79
Which versions are affected by CVE-2020-26956?
It affects 3 products.
Products include Mozilla Firefox, Mozilla Firefox Esr, Mozilla Thunderbird.
How do I fix CVE-2020-26956?
Upgrade to a fixed version.
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-2020-26956 being exploited?
There is no known exploitation of CVE-2020-26956 in the wild and no public exploit code.
Other vulnerabilities in Mozilla Firefox
Sources
Also known as DEBIAN-CVE-2020-26956, GHSA-2rfm-q54c-ww9j, UBUNTU-CVE-2020-26956.