CVE-2026-4371 · cross-distro fix matrix

CVE-2026-4371: A malicious mail server could send malformed strings with negative lengths, causing the parser to read memory outside the buffer. If a mail server or connection to a mail server were compromised, an attacker could cause the parser to malfunction, potentially crashing Thunderbird or leaking sensitive

Affects 3 Linux releases across 3 (distro × package) combinations.

Fix per ecosystem

Each block below is a distro release where CVE-2026-4371 has a known fix. Run the listed command on that distro to remediate.

Debian bullseye

Source: Debian Security Tracker

thunderbird→ fixed in1:140.9.0esr-1~deb11u1urgency: not yet assigned
```
sudo apt-get install --only-upgrade -y thunderbird
```

Debian bookworm

Source: Debian Security Tracker

thunderbird→ fixed in1:140.9.0esr-1~deb12u1urgency: not yet assigned
```
sudo apt-get install --only-upgrade -y thunderbird
```

Debian trixie

Source: Debian Security Tracker

thunderbird→ fixed in1:140.9.0esr-1~deb13u1urgency: not yet assigned
```
sudo apt-get install --only-upgrade -y thunderbird
```

Are YOU affected by CVE-2026-4371?

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.

curl https://mindsparkstack.com/scan.sh | bash

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