Integer Overflow or Wraparound Affecting haproxy package, versions [,3.5-dev1)
Threat Intelligence
The probability is the direct output of the EPSS model, and conveys an overall sense of the threat of exploitation in the wild. The percentile measures the EPSS probability relative to all known EPSS scores. Note: This data is updated daily, relying on the latest available EPSS model version. Check out the EPSS documentation for more details.
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- published28 Jun 2026
- disclosed18 Jun 2026
- creditUnknown
Introduced: 18 Jun 2026
CVE-2026-55203 (opens in a new tab)How to fix?
Upgrade haproxy to version 3.5-dev1 or higher.
Overview
Affected versions of this package are vulnerable to Integer Overflow or Wraparound in the fcgi_conn process when handling FCGI demux record length fields. An attacker can cause incorrect record consumption, desynchronize the FCGI framing parser, and potentially trigger request routing errors, response smuggling, or memory safety issues by sending specially crafted FastCGI responses with a contentLength of 65535 and a paddingLength of 1 or more.