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6.5
Firefox ESR allows cookie overwrite from insecure subdomains
published 5 days ago
Summary
The Firefox ESR web browser can be tricked into accepting specially crafted cookies on a non‑secure part of a shared website. This lets an attacker replace cookies that were set in a secure context, potentially taking over user sessions. Update Firefox ESR to the latest version as soon as possible to fix the issue.
What to do
- Update cleanstart firefox-esr to version 102.3.0-r0.
Affected software
| Ecosystem | Vendor | Product | Affected versions |
|---|---|---|---|
| CleanStart | cleanstart | firefox-esr |
< 102.3.0-r0 Fix: upgrade to 102.3.0-r0
|
Original advisory text
By injecting a cookie with certain special characters, an attacker on a shared subdomain which is not a secure context could set and thus overwrite cookies from a secure context, leading to session...
Security vulnerability affects the firefox-esr package. By injecting a cookie with certain special characters, an attacker on a shared subdomain which is not a secure context could set and thus overwrite cookies from a secure context, leading to session fixation and other attacks.
Internet-facing
60 days
Internal
At next upgrade
- Not known to be exploited
- Needs hands-on effort to exploit (estimated)
- Gives an attacker partial control (estimated)
Timeline
Published30 Oct 2026
Updated31 Oct 2026
First seen31 Oct 2026
Sources
CLEANSTART-2024-SQ11042 · OSV
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