CVE-2026-12304 · cross-distro fix matrix

CVE-2026-12304: Same-origin policy bypass in the Networking: Cookies component. This vulnerability was fixed in Firefox 152, Firefox ESR 140.12, Thunderbird 152, and Thunderbird 140.12.

Affects 3 Linux releases across 6 (distro × package) combinations. First disclosed: 2026-06-16.

CVSS v3:CRITICAL · 9.1(NVD-published)

Fix per ecosystem

Each block below is a distro release where CVE-2026-12304 has a known fix. Run the listed command on that distro to remediate.

Debian bullseye

Source: Debian Security Tracker

firefox-esr→ fixed in140.12.0esr-1~deb11u1urgency: not yet assigned
```
sudo apt-get install --only-upgrade -y firefox-esr
```
thunderbird→ fixed in1:140.12.0esr-1~deb11u1urgency: not yet assigned
```
sudo apt-get install --only-upgrade -y thunderbird
```

Debian bookworm

Source: Debian Security Tracker

firefox-esr→ fixed in140.12.0esr-1~deb12u1urgency: not yet assigned
```
sudo apt-get install --only-upgrade -y firefox-esr
```
thunderbird→ fixed in1:140.12.0esr-1~deb12u1urgency: not yet assigned
```
sudo apt-get install --only-upgrade -y thunderbird
```

Debian trixie

Source: Debian Security Tracker

firefox-esr→ fixed in140.12.0esr-1~deb13u1urgency: not yet assigned
```
sudo apt-get install --only-upgrade -y firefox-esr
```
thunderbird→ fixed in1:140.12.0esr-1~deb13u1urgency: not yet assigned
```
sudo apt-get install --only-upgrade -y thunderbird
```

Are YOU affected by CVE-2026-12304?

5-second check on your actual server. Reads /etc/os-release, uname -r, and the distro's package manager; matches against this same cross-source index live.

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