Summary
Libsoup is an HTTP library implementation in C. It was originally part of a SOAP (Simple Object Access Protocol) implementation called Soup, but the SOAP and non-SOAP parts have now been split into separate packages. libsoup uses the Glib main loop and is designed to work well with GTK applications. This enables GNOME applications to access HTTP servers on the network in a completely asynchronous fashion, very similar to the Gtk+ programming model (a synchronous operation mode is also supported for those who want it), but the SOAP parts were removed long ago.
Security Fix(es):
* SoupWebsocketExtensionDeflate: libsoup: libsoup: WebSocket permessage-deflate Unbounded Decompression Remote Denial of Service (CVE-2026-15709)
* libsoup: SoupWebsocketConnection: libsoup: WebSocket remote denial of service via oversized control frame protocol violation (CVE-2026-15711)
* libsoup: libsoup: Heap use-after-free in libsoup HTTP/2 client on_data_read() via GOAWAY during body upload (CVE-2026-85197)
For more details about the security issue(s), including the impact, a CVSS score, acknowledgments, and other related information, refer to the CVE page(s) listed in the References section.
Fixed packages 3
| Release | Package | Fixed in |
|---|---|---|
| AlmaLinux · 10 | libsoup3 | 3.6.5-3.el10_2.14 |
| AlmaLinux · 10 | libsoup3-devel | 3.6.5-3.el10_2.14 |
| AlmaLinux · 10 | libsoup3-doc | 3.6.5-3.el10_2.14 |
Vulnerabilities 3
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High 7.6
Libsoup: libsoup: heap use-after-free in libsoup http/2 client on_data_read() via goaway during body upload
A flaw was found in libsoup. A malicious HTTP/2 server or a Man-in-the-Middle (MITM) attacker can exploit a heap use-after-free vulnerability in the HTTP/2 client implementation. This occurs when a GNOME application uploads a file using HTTP/2, and the server…
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High 7.5
Soupwebsocketextensiondeflate: libsoup: libsoup: websocket permessage-deflate unbounded decompression remote denial of service
A flaw was found in libsoup's WebSocket implementation when using the permessage-deflate extension. The extension's decompression loop (inflate()) processes data in chunks without enforcing an upper boundary limit on the output buffer size. While libsoup limi…
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High 7.5
Libsoup: soupwebsocketconnection: libsoup: websocket remote denial of service via oversized control frame protocol violation
A vulnerability was found in libsoup's WebSocket frame parsing implementation. The library fails to validate length rules specified in RFC 6455 §5.5, which mandates that all WebSocket control frames (e.g., PING, PONG, CLOSE) contain a payload of 125 bytes or …
References
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report
https://access.redhat.com/security/cve/CVE-2026-15709
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report
https://access.redhat.com/security/cve/CVE-2026-15711
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report
https://access.redhat.com/security/cve/CVE-2026-85197
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report
https://bugzilla.redhat.com/2499922
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report
https://bugzilla.redhat.com/2499924
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report
https://bugzilla.redhat.com/2528425
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advisory
https://errata.almalinux.org/10/ALSA-2026-68235.html