Bug 2543296 (CVE-2026-102560) - CVE-2026-102560 libsoup: libsoup: Heap buffer overflow during outgoing permessage-deflate buffer growth
Summary: CVE-2026-102560 libsoup: libsoup: Heap buffer overflow during outgoing permes...
Keywords:
Status: NEW
Alias: CVE-2026-102560
Product: Security Response
Classification: Other
Component: vulnerability
Version: unspecified
Hardware: All
OS: Linux
high
high
Target Milestone: ---
Assignee: Product Security
QA Contact:
URL:
Whiteboard:
Depends On:
Blocks:
TreeView+ depends on / blocked
 
Reported: 2026-09-29 16:50 UTC by OSIDB Bzimport
Modified: 2026-09-29 16:59 UTC (History)
2 users (show)

Fixed In Version:
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Description OSIDB Bzimport 2026-09-29 16:50:24 UTC 
A heap buffer overflow was found in libsoup's WebSocket permessage-deflate outgoing path.

soup_websocket_extension_deflate_process_outgoing_message() stored deflateBound()'s uLong result in a guint and grew a GByteArray by that amount. For payloads approaching 4 GiB, the bound exceeds G_MAXUINT; truncation allowed buffer->len + max_length to wrap on later growth, and zlib wrote through next_out past the allocation.

Fixed by refusing payloads whose compressed bound cannot fit in a GByteArray and by checking each incremental growth (commit dbd0417e, libsoup 3.7.3).

References:
https://gitlab.gnome.org/GNOME/libsoup/-/work_items/554 (Bug 8)
https://gitlab.gnome.org/GNOME/libsoup/-/commit/dbd0417e
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