What’s Vulnerable › Vulnerabilities

CVE-2023-40225

• Severity: high (CVSS 7.2 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 2.1% probability of exploitation in the next 30 days
• Public exploit or detection template: yes
• Published: 2023-08-10 · updated 2026-06-17
• Weakness: CWE-444

Description

HAProxy through 2.0.32, 2.1.x and 2.2.x through 2.2.30, 2.3.x and 2.4.x through 2.4.23, 2.5.x and 2.6.x before 2.6.15, 2.7.x before 2.7.10, and 2.8.x before 2.8.2 forwards empty Content-Length headers, violating RFC 9110 section 8.6. In uncommon cases, an HTTP/1 server behind HAProxy may interpret the payload as an extra request.

Affected products

• HAProxy: through 2.0.32; from 2.2.0 through 2.2.30; from 2.4.0 through 2.4.23; from 2.5.0 before 2.6.15; from 2.7.0 before 2.7.10; from 2.8.0 before 2.8.2 — fixed in 2.6.15, 2.7.10, 2.8.2

How to fix

Upgrade to a fixed version: HAProxy 2.6.15, 2.7.10, 2.8.2. Check the vendor advisory for mitigations.

References

• https://cwe.mitre.org/data/definitions/436.html
• https://github.com/haproxy/haproxy/commit/6492f1f29d738457ea9f382aca54537f35f9d856
• https://github.com/haproxy/haproxy/issues/2237
• https://www.haproxy.org/download/2.6/src/CHANGELOG
• https://www.haproxy.org/download/2.7/src/CHANGELOG
• https://www.haproxy.org/download/2.8/src/CHANGELOG
• https://cwe.mitre.org/data/definitions/436.html
• https://github.com/haproxy/haproxy/commit/6492f1f29d738457ea9f382aca54537f35f9d856
• https://github.com/haproxy/haproxy/issues/2237
• https://www.haproxy.org/download/2.6/src/CHANGELOG
• https://www.haproxy.org/download/2.7/src/CHANGELOG
• https://www.haproxy.org/download/2.8/src/CHANGELOG

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