Description
A flaw in libsoup’s HTTP header handling allows multiple Host: headers in a request and returns the last occurrence for server-side processing. Common front proxies often honor the first Host: header, so this mismatch can cause vhost confusion where a proxy routes a request to one backend but the backend interprets it as destined for another host. This discrepancy enables request-smuggling style attacks, cache poisoning, or bypassing host-based access controls when an attacker supplies duplicate Host headers.
References10
- access.redhat.com/errata/RHSA-2026:0421
- access.redhat.com/errata/RHSA-2026:0422
- access.redhat.com/errata/RHSA-2026:0423
- access.redhat.com/errata/RHSA-2026:0836
- access.redhat.com/errata/RHSA-2026:0867
- access.redhat.com/errata/RHSA-2026:0868
- access.redhat.com/errata/RHSA-2026:0905
- access.redhat.com/errata/RHSA-2026:0906
- access.redhat.com/errata/RHSA-2026:0907
- access.redhat.com/errata/RHSA-2026:0908
Metrics
- CVSS 3.1
-
8.2
HIGH
Score source: CNA
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:H/A:N - EPSS — exploit probability
- 1% percentile: 48 · as of 11 November 2026
- CWE
- CWE-444
Could this be exploited in your environment?
A patch closes the known hole. A penetration test shows what an attacker can still reach — with proof.