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CVE-2026-55203

HAProxy - Integer Overflow in FCGI Demux Record Length Field

Published: Jun 18, 2026Updated: Jul 14, 2026 Sources: CVE List NVDCWE-190
7.5HIGH
NVD MITRE
EPSS Score
0.3%
Top 72.6%
CISA KEV
Not in KEV
Exploits
No Known Exploits
Remediation
Patch Available
Self-Check
OpenVAS

Description

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.

No summary for this CVE yet.

CVSS Vector Breakdown

AV:NAC:HPR:NUI:NS:CC:LI:HA:N
Exploitability
AV:NAttack Vector
Network
AC:HAttack Complexity
High
PR:NPrivileges Required
None
UI:NUser Interaction
None
Scope
S:CScope
Changed
Impact
C:LConfidentiality
Low
I:HIntegrity
High
A:NAvailability
None
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Weaknesses

CWE-190

Affected Products

haproxy
oss-project·FRaka haproxy enterprise, aloha appliance
haproxyOn-prem
Networking Infrastructure / load-balancer-proxy

Exploitability

Official Patch Available
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Attack Graph

Products CVE Techniques Tactics

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MITRE ATT&CK

1 technique
Initial Access
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References

https://github.com/haproxy/haproxy/commit/5985276735777634d8c85f1d73bb7764aab0d6dd
github.com
https://www.vulncheck.com/advisories/haproxy-integer-overflow-in-fcgi-demux-record-length-field
vulncheck.com
News mentions
1

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