MediumFix available
libsoup3 — security advisory
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.
- Products
- libsoup3
- Affected versions
- 3.0.4-2, 3.0.4-3, 3.0.5-1, 3.0.7-0ubuntu1, 3.0.7-0ubuntu1+esm1, 3.0.7-0ubuntu1+esm2, 3.0.7-0ubuntu1+esm3, 3.0.7-0ubuntu1+esm4, 3.0.7-0ubuntu1+esm5, 3.0.7-0ubuntu1+esm6, 3.0.7-0ubuntu1+esm7, 3.0.7-0ubuntu1+esm8, 3.4.2-4, 3.4.4-1, 3.4.4-2, 3.4.4-4, 3.4.4-5, 3.4.4-5build1, 3.4.4-5build2, 3.4.4-5ubuntu0.1, 3.4.4-5ubuntu0.2, 3.4.4-5ubuntu0.3, 3.4.4-5ubuntu0.4, 3.4.4-5ubuntu0.5, 3.4.4-5ubuntu0.6, 3.4.4-5ubuntu0.7, 3.4.4-5ubuntu0.8, 3.6.5-4, 3.6.5-5, 3.6.5-6, 3.6.5-7, 3.6.5-9, 3.6.6-1
- Fixed versions
- 3.0.7-0ubuntu1+esm9, 3.4.4-5ubuntu0.9, 3.6.6-1ubuntu0.1, 3.6.6-1ubuntu3
- CVEs
- CVE-2026-85534
- Confirmed fixed CVEs
- Not specified
- Updated in this feed
- 31 Oct 2026, 17:41 UTC · Revision 1
Source evidence
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.
osv:UBUNTU-CVE-2026-85534
libsoup3
Fixed versions: 3.0.7-0ubuntu1+esm9
libsoup3
Fixed versions: 3.4.4-5ubuntu0.9
libsoup3
Fixed versions: 3.6.6-1ubuntu3
libsoup3
Fixed versions: 3.6.6-1ubuntu0.1
Complete source record
{
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"url": "https://osv.dev/vulnerability/UBUNTU-CVE-2026-85534",
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"summary": "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.",
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"3.0.7-0ubuntu1+esm2",
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"3.0.7-0ubuntu1+esm4",
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"3.0.7-0ubuntu1+esm6",
"3.0.7-0ubuntu1+esm7",
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"modified": "2026-10-22T04:41:54.118981837Z",
"provider": "osv",
"upstream": [
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"references": [
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"https://www.cve.org/CVERecord?id=CVE-2026-85534",
"https://gitlab.gnome.org/GNOME/libsoup/-/work_items/551",
"https://gitlab.gnome.org/GNOME/libsoup/-/merge_requests/561",
"https://ubuntu.com/security/notices/USN-8890-1",
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"source_id": "core-osv",
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"published_at": "2026-09-04T11:17:00+00:00"
}