Description
An information leak vulnerability was discovered in HAProxy 2.1, 2.2 before 2.2.27, 2.3, 2.4 before 2.4.21, 2.5 before 2.5.11, 2.6 before 2.6.8, 2.7 before 2.7.1. There are 5 bytes left uninitialized in the connection buffer when encoding the FCGI_BEGIN_REQUEST record. Sensitive data may be disclosed to configured FastCGI backends in an unexpected way.
Affected products
| Vendor | Product | Affected | Fixed |
|---|---|---|---|
| — | HAProxy | HAProxy 2.8, HAProxy 2.7.1, HAProxy 2.6.8, HAProxy 2.5.11, HAProxy 2.4.21, HAProxy 2.2.27 | — |
Fixed in Linux distributions
Distributions backport fixes, so the version that fixes this vulnerability differs per release — upgrade to at least the version shown. From the distributions' security trackers and advisories.
Debian
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian 14 | haproxy | 2.6.8-1 | — |
| Debian 13 | haproxy | 2.6.8-1 | — |
| Debian 12 | haproxy | 2.6.8-1 | — |
| Debian 11 | haproxy | 2.2.9-2+deb11u5 | DSA-5388-1 |
Ubuntu
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu 22.04 LTS | haproxy | 2.4.18-0ubuntu1.3 | USN-5994-1 |
Red Hat
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| RHEL 9 | haproxy | 2.4.22-1.el9 | RHSA-2023:6496 |
AlmaLinux
Errata ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| AlmaLinux 9 | haproxy | 2.4.22-1.el9 | ALSA-2023:6496 |
Oracle Linux
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Oracle Linux 9 | haproxy | 2.4.22-1.el9 | ELSA-2023-6496 |
Advisories 6
- ALSA-2023:6496 Moderate: haproxy security and bug fix update AlmaLinux Security Advisories · Oct 29, 2026
- DSA-5388-1 haproxy - security update Debian Security (DSA / DLA) · Mar 9, 2026
- USN-5994-1 haproxy vulnerability Ubuntu Security Notices (USN) · Feb 10, 2026
- RHSA-2023:6496 Red Hat Security Advisory: haproxy security and bug fix update Red Hat Security Advisories (RHSA) · Jan 29, 2026
- ELSA-2023-6496 Moderate: haproxy security and bug fix update (Oracle Linux 9) Oracle Linux Security Advisories (ELSA) · Nov 11, 2023
- WID-SEC-2023-0716 HAProxy Enterprise: Schwachstelle ermöglicht Offenlegung von Informationen BSI CERT-Bund (WID) · Nov 7, 2023