Quick answers
- Is CVE-2026-66337 exploited in the wild?
- No. Junglewise Threat Intelligence has no report of CVE-2026-66337 being exploited in the wild.
- How severe is CVE-2026-66337?
- Medium severity, with a CVSS score of 6.5, published 24 July 2026.
- Which products and versions are affected?
- Gnome Libsoup Red Hat Enterprise Linux 10.
- Is there a fix for CVE-2026-66337?
- No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.
- How is CVE-2026-66337 attacked?
- It is attacked over the network, in a software library.
- Am I affected by CVE-2026-66337?
- Check whether you run Gnome Libsoup at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.
Technical details
An unsigned integer underflow exists in the `soup_filter_input_stream_read_until()` function within `libsoup/soup-filter-input-stream.c`. When the `include_boundary` parameter is set to FALSE and the internal buffer contains fewer bytes than the boundary string length, a subtraction operation wraps to a large value. This causes the boundary scan loop to perform an out-of-bounds read (CWE-125) on the heap. A malicious HTTP server can exploit this by sending a crafted multipart response to a client using `SoupMultipartInputStream`. The vulnerability can result in a Denial of Service (crash) or the disclosure of sensitive heap memory.
Affected products
- Red Hat libsoup3 Red Hat Enterprise Linux 10
- Red Hat libsoup Red Hat Enterprise Linux 6, 7, 8, 9
- GNOME libsoup
Timeline
- 2026-07-24: disclosed: Initial report via Red Hat Bugzilla and NVD publication