What’s Vulnerable › Vulnerabilities

CVE-2021-39240

• Severity: high (CVSS 7.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 2.2% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2021-08-17 · updated 2026-06-17

Description

An issue was discovered in HAProxy 2.2 before 2.2.16, 2.3 before 2.3.13, and 2.4 before 2.4.3. It does not ensure that the scheme and path portions of a URI have the expected characters. For example, the authority field (as observed on a target HTTP/2 server) might differ from what the routing rules were intended to achieve.

Affected products

• Debian Linux: 11.0
• Fedoraproject Fedora: 33, 34
• HAProxy: from 2.2.0 before 2.2.16; from 2.3.0 before 2.3.13; from 2.4.0 before 2.4.3 — fixed in 2.2.16, 2.3.13, 2.4.3

How to fix

Upgrade to a fixed version: HAProxy 2.2.16, 2.3.13, 2.4.3. Check the vendor advisory for mitigations.

References

• https://git.haproxy.org/?p=haproxy.git%3Ba=commit%3Bh=4b8852c70d8c4b7e225e24eb58258a15eb54c26e
• https://git.haproxy.org/?p=haproxy.git%3Ba=commit%3Bh=a495e0d94876c9d39763db319f609351907a31e8
• https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/4ALECUZDIMT5FYGP6V6PVSI4BKVZTZWN/
• https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/RPNY4WZIQUAUOCLIMUPC37AQWNXTWIQM/
• https://www.debian.org/security/2021/dsa-4960
• https://www.mail-archive.com/haproxy%40formilux.org/msg41041.html
• https://git.haproxy.org/?p=haproxy.git%3Ba=commit%3Bh=4b8852c70d8c4b7e225e24eb58258a15eb54c26e
• https://git.haproxy.org/?p=haproxy.git%3Ba=commit%3Bh=a495e0d94876c9d39763db319f609351907a31e8
• https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/4ALECUZDIMT5FYGP6V6PVSI4BKVZTZWN/
• https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/RPNY4WZIQUAUOCLIMUPC37AQWNXTWIQM/
• https://www.debian.org/security/2021/dsa-4960
• https://www.mail-archive.com/haproxy%40formilux.org/msg41041.html

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