HAProxy through 3.4.0, fixed in commit 5985276, contains an integer overflow vulnerability in the fcgi_conn structure's drl field that allows buffer misparse as new FCGI record headers. When contentLength is 65535 and paddingLength is 1 or more, the drl field wraps to 0, causing incorrect record consumption and allowing malicious FastCGI backends to desynchronize the FCGI framing parser, potentially causing request routing errors, response smuggling, or memory safety issues.
CVSS Details
- CVSS 4.0 Base Score: 9 (CRITICAL)
- CVSS 4.0 Vector: (CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:H/VA:N/SC:L/SI:H/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X)
- CVSS 3.1 Base Score: 9.1
- CVSS 3.1 Vector: (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H)
Covered by Rapid7
| Product | Vendor Advisory | Solution File | Added | Published |
|---|---|---|---|---|
| Alma_linux | — | Upgrade haproxy | Oct 11, 2026 | Aug 17, 2026 |
| Oracle_linux | — | Upgrade haproxy | Oct 22, 2026 | Jun 18, 2026 |
| Redhat_linux | — | Upgrade haproxy-debuginfoNo solution existsUpgrade haproxyUpgrade haproxy-debugsource | Jul 20, 2026 | Jun 18, 2026 |
| Rocky_linux | — | Upgrade haproxyUpgrade haproxy-debugsourceUpgrade haproxy-debuginfo | Aug 20, 2026 | Aug 18, 2026 |
| Ubuntu | — | Upgrade haproxy | Jun 23, 2026 | Jun 22, 2026 |
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