CVE-2026-53900 Cookie injection was possible when opening a PDF link
A malicious site could inject arbitrary cookies into requests to unrelated domains via PDF links in Firefox for iOS, bypassing security controls.
- 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-2026-53900?
CVE-2026-53900 is a medium-severity vulnerability in Mozilla Firefox Mobile, published on 16 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
Firefox for iOS preserved cookies set on the initial PDF request across cross-origin HTTP redirects in TemporaryDocument, allowing a malicious site to inject arbitrary cookies into requests to an unrelated target domain. This vulnerability was fixed in Firefox for iOS 152.0.
Which versions are affected by CVE-2026-53900?
It affects 1 product.
Products include Mozilla Firefox Mobile.
How do I fix CVE-2026-53900?
No fix has been published for CVE-2026-53900 yet. Limit exposure of the affected software until one is available.
Is CVE-2026-53900 being exploited?
There is no known exploitation of CVE-2026-53900 in the wild and no public exploit code.
Other vulnerabilities in Mozilla Firefox Mobile
Sources
Also known as GHSA-6xv8-mg86-mq56.