CVE-2026-2708: Libsoup: libsoup: http request smuggling via duplicate content-length headers

Severity: medium (CVSS 5.3 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.3% probability of exploitation in the next 30 days
Public exploit or detection template: yes
Published: 2026-04-23 · updated 2026-10-26
Weakness: CWE-444

Description

A request smuggling vulnerability exists in libsoup's HTTP/1 header parsing logic. The soup_message_headers_append_common() function in libsoup/soup-message-headers.c unconditionally appends each header value without validating for duplicate or conflicting Content-Length fields. This allows an attacker to send HTTP requests containing multiple Content-Length headers with differing values.

Affected products

GNOME libsoup: all versions
Red Hat Enterprise Linux: 6.0, 7.0, 8.0, 9.0, 10.0

References

https://access.redhat.com/security/cve/CVE-2026-2708
https://bugzilla.redhat.com/show_bug.cgi?id=2440743
https://gitlab.gnome.org/GNOME/libsoup/-/issues/500
https://gitlab.gnome.org/GNOME/libsoup/-/merge_requests/513

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