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CVE

CVE-2026-55203

HAProxy - Integer Overflow in FCGI Demux Record Length Field
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CVE

CVE-2026-55203

HAProxy - Integer Overflow in FCGI Demux Record Length Field

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.

Package Versions Affected

Package Version
patch Availability
No items found.

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CVSS Version

Severity
Base Score
CVSS Version
Score Vector
C
H
U
9
-
4.0
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
C
H
U
0
-
C
H
U
-

Related Resources

No items found.

References

https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/55xxx/CVE-2026-55203.json, https://nvd.nist.gov/vuln/detail/CVE-2026-55203, https://www.vulncheck.com/advisories/haproxy-integer-overflow-in-fcgi-demux-record-length-field, https://github.com/haproxy/haproxy/commit/5985276735777634d8c85f1d73bb7764aab0d6dd, https://github.com/haproxy/haproxy

Severity

0

CVSS Score
0
10

Basic Information

Base CVSS
0
EPSS Probability
0.00321%
EPSS Percentile
0.24055%
Introduced Version
0
Fix Available
5985276735777634d8c85f1d73bb7764aab0d6dd,0:2.8.16-0ubuntu0.24.04.3,0:2.4.30-0ubuntu0.22.04.2,2.4.36-r0,2.6.31-r0,2.8.26-r0,3.0.24-r0,3.2.20-r0,3.3.11-r0

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