CVE-2023-25725

Severity: critical (CVSS 9.1 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 5.4% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2023-02-14 · updated 2026-06-17
Weakness: CWE-444

Description

HAProxy before 2.7.3 may allow a bypass of access control because HTTP/1 headers are inadvertently lost in some situations, aka "request smuggling." The HTTP header parsers in HAProxy may accept empty header field names, which could be used to truncate the list of HTTP headers and thus make some headers disappear after being parsed and processed for HTTP/1.0 and HTTP/1.1. For HTTP/2 and HTTP/3, the impact is limited because the headers disappear before being parsed and processed, as if they had not been sent by the client. The fixed versions are 2.7.3, 2.6.9, 2.5.12, 2.4.22, 2.2.29, and 2.0.31.

Affected products

Debian Linux: 10.0, 11.0
HAProxy: before 2.0.31; from 2.1.0 before 2.2.29; from 2.3.0 before 2.4.22; from 2.5.0 before 2.5.12; from 2.6.0 before 2.6.9; from 2.7.0 before 2.7.3 — fixed in 2.0.31, 2.2.29, 2.4.22, 2.5.12, 2.6.9, 2.7.3

How to fix

Upgrade to a fixed version: HAProxy 2.0.31, 2.2.29, 2.4.22, 2.5.12. Check the vendor advisory for mitigations.

References

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