What’s Vulnerable › Vulnerabilities

CVE-2026-85534: Libsoup: libsoup: http/2 client crash in on_data_source_read_callback when settings initial_window_size shrinks during deferred body read

• Severity: medium (CVSS 5.9 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: none known
• Published: 2026-09-04 · updated 2026-09-08
• Weakness: CWE-617

Description

A flaw was found in libsoup. When a client sends an HTTP/2 request body from a non-pollable input stream, the library can buffer more data than the current flow-control window later allows. A malicious HTTP/2 server can shrink SETTINGS_INITIAL_WINDOW_SIZE while that buffered read is still in progress. The client then copies the full buffer into a smaller DATA callback without a runtime bounds check, which can abort the process or fail the HTTP/2 session.

Affected products

• Red Hat Enterprise Linux 10: all versions

References

• https://access.redhat.com/security/cve/CVE-2026-85534
• https://bugzilla.redhat.com/show_bug.cgi?id=2528440
• https://gitlab.gnome.org/GNOME/libsoup/-/blob/master/libsoup/http2/soup-client-message-io-http2.c
• https://gitlab.gnome.org/GNOME/libsoup/-/work_items/551

Get alerted when CVE-2026-85534 or the next vulnerability affects your stack