CVE-2026-66337: Libsoup: libsoup: heap buffer over-read via integer underflow in soup_filter_input_stream_read_until()

Severity: medium (CVSS 6.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.2% probability of exploitation in the next 30 days
Public exploit or detection template: yes
Published: 2026-07-24 · updated 2026-08-24
Weakness: CWE-125

Description

A flaw was found in libsoup. An unsigned integer underflow in the soup_filter_input_stream_read_until() function causes a heap buffer over-read when parsing multipart HTTP responses. A malicious HTTP server can exploit this by sending a crafted multipart response, potentially causing the client application to crash or disclose sensitive heap memory.

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-2026-66337
https://bugzilla.redhat.com/show_bug.cgi?id=2506949

Get alerted when CVE-2026-66337 or the next vulnerability affects your stack