CVE-2026-12549: Libsoup: incomplete fix for cve-2026-2443: range suffix overflow in libsoup soupserver

Severity: medium (CVSS 4.8 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.4% probability of exploitation in the next 30 days
Public exploit or detection template: yes
Published: 2026-06-22 · updated 2026-07-08
Weakness: CWE-805

Description

The fix for CVE-2026-2443 was regressed by a subsequent rework commit that replaced specific overflow checks with a general signed comparison. When a client sends a Range request with a suffix length exceeding the content size, the resulting negative start value is not properly clamped, leading to malformed HTTP 206 responses and log flooding.

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-2026-12549
https://access.redhat.com/security/cve/cve-2026-0716
https://bugzilla.redhat.com/show_bug.cgi?id=2489999
https://gitlab.gnome.org/GNOME/libsoup/-/work_items/516

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