CVE-2026-55203 · cross-distro fix matrix

CVE-2026-55203: It was discovered that HAProxy incorrectly handled the FCGI demultiplexer

Affects 4 Linux releases across 12 (distro × package) combinations. First disclosed: 2026-06-18.

CVSS v3:HIGH · 7.5(NVD-published)

Fix per ecosystem

Each block below is a distro release where CVE-2026-55203 has a known fix. Run the listed command on that distro to remediate.

Ubuntu jammy

Source: Ubuntu USN

haproxy→ fixed in2.4.30-0ubuntu0.22.04.2USN-8459-1
```
sudo apt-get install --only-upgrade -y haproxy
```
haproxy-doc→ fixed in2.4.30-0ubuntu0.22.04.2USN-8459-1
```
sudo apt-get install --only-upgrade -y haproxy-doc
```
vim-haproxy→ fixed in2.4.30-0ubuntu0.22.04.2USN-8459-1
```
sudo apt-get install --only-upgrade -y vim-haproxy
```

Ubuntu noble

Source: Ubuntu USN

haproxy→ fixed in2.8.16-0ubuntu0.24.04.3USN-8459-1
```
sudo apt-get install --only-upgrade -y haproxy
```
haproxy-doc→ fixed in2.8.16-0ubuntu0.24.04.3USN-8459-1
```
sudo apt-get install --only-upgrade -y haproxy-doc
```
vim-haproxy→ fixed in2.8.16-0ubuntu0.24.04.3USN-8459-1
```
sudo apt-get install --only-upgrade -y vim-haproxy
```

Ubuntu questing

Source: Ubuntu USN

haproxy→ fixed in3.0.12-0ubuntu0.25.10.5USN-8459-1
```
sudo apt-get install --only-upgrade -y haproxy
```
haproxy-doc→ fixed in3.0.12-0ubuntu0.25.10.5USN-8459-1
```
sudo apt-get install --only-upgrade -y haproxy-doc
```
vim-haproxy→ fixed in3.0.12-0ubuntu0.25.10.5USN-8459-1
```
sudo apt-get install --only-upgrade -y vim-haproxy
```

Ubuntu resolute

Source: Ubuntu USN

haproxy→ fixed in3.2.9-1ubuntu2.2USN-8459-1

sudo apt-get install --only-upgrade -y haproxy

haproxy-doc→ fixed in3.2.9-1ubuntu2.2USN-8459-1

sudo apt-get install --only-upgrade -y haproxy-doc

vim-haproxy→ fixed in3.2.9-1ubuntu2.2USN-8459-1

sudo apt-get install --only-upgrade -y vim-haproxy

Are YOU affected by CVE-2026-55203?

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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Continuous monitoring beats manual checking

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