Executive brief
libsoup is a widely used HTTP client/server library for GNOME and Linux systems. A flaw in how it handles specific web requests (Range requests) allows an unauthenticated attacker to trigger malformed responses and flood system logs with error messages. In some development or debug environments, this could also cause the application to crash, potentially leading to a service outage.
Technical details
A regression in libsoup (specifically in soup-message-headers.c) occurred when a rework commit replaced specific overflow checks with a general signed comparison. When a client sends an HTTP Range request with a suffix length (e.g., 'bytes=-N') exceeding the total content length, the library calculates a negative start offset. Because of a signed comparison error (treating the negative start as larger than the end), the value is not clamped to zero. This results in malformed Content-Range headers, GLib-CRITICAL log flooding, and potential SIGABRT crashes in debug builds when the negative value is passed to memory functions. The vulnerability affects both libsoup 2.x and 3.x branches.
Affected products
- Red Hat libsoup3 3.4.x, 3.6.x
- GNOME libsoup master, 3.4.x, 3.6.x
- Red Hat Red Hat Enterprise Linux 8
- Red Hat Red Hat Enterprise Linux 9
- Red Hat Red Hat Enterprise Linux 10
Timeline
- 2026-06-17: disclosed: Issue reported to GNOME/Red Hat Bugzilla
- 2026-06-22: advisory: NVD and Red Hat published advisory details