CVE-2026-55203
7.5 · HIGHOverview
CVE-2026-55203 is a high-severity vulnerability affecting haproxy haproxy. It was published on June 18, 2026 and has a CVSS 3.1 base score of 7.5 (HIGH).
This vulnerability has a CVSS 3.1 base score of 7.5, rated HIGH. It can be exploited remotely over the network. No authentication or special privileges are required for exploitation.
Technical 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.
Remediation
Check the references section for vendor advisories and patches from haproxy. Update haproxy to the latest patched version. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.
Affected Products
| Vendor | Product | Versions | Status |
|---|---|---|---|
| haproxy | haproxy | 0 | Affected |
Frequently Asked Questions
What is CVE-2026-55203?
CVE-2026-55203 is a high-severity vulnerability affecting haproxy haproxy. It was published on June 18, 2026 and has a CVSS 3.1 base score of 7.5 (HIGH).
How severe is CVE-2026-55203?
This vulnerability has a CVSS 3.1 base score of 7.5, rated HIGH. It can be exploited remotely over the network. No authentication or special privileges are required for exploitation.
How do I fix or remediate CVE-2026-55203?
Check the references section for vendor advisories and patches from haproxy. Update haproxy to the latest patched version. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.
How can CyberStrike help with CVE-2026-55203?
CyberStrike's AI-powered security agents can automatically detect CVE-2026-55203 across your infrastructure using autonomous pentesting, DAST scanning, and HackBrowser. The platform continuously monitors for known vulnerabilities and provides actionable remediation guidance prioritized by real-world exploitability.
How CyberStrike Helps
AI agents map your attack surface to find vulnerabilities like this one.
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