Libsoup3: 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… (CVE-2026-85534)
Description
A denial of service vulnerability exists in libsoup 3 HTTP/2 client when uploading a request body from a non-pollable input stream to a malicious HTTP/2 server that reduces the SETTINGS_INITIAL_WINDOW_SIZE during deferred read. This causes excessive buffering and triggers an assertion failure, aborting the client process or dropping the HTTP/2 session. The flaw affects libsoup versions 3.0.0 and later up to certain patched versions.
CVSS v3.1
Score 5.9medium
Affected software
pkg:deb/ubuntu/libsoup3?arch=source&distro=esm-apps/jammypkg:deb/ubuntu/libsoup3?arch=source&distro=noblepkg:deb/ubuntu/libsoup3?arch=source&distro=stonkingpkg:deb/ubuntu/libsoup3?arch=source&distro=resoluteRun on your own infrastructure? Check whether these packages are installed with threat-finder — our free open-source scanner.
Weaknesses
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
CVE-2026-85534 is a denial of service vulnerability in libsoup 3's HTTP/2 client implementation. When a client sends an HTTP/2 request body from a non-pollable input stream to a malicious server that shrinks the SETTINGS_INITIAL_WINDOW_SIZE during deferred read, the client buffers more data than allowed. This triggers an assertion failure, causing the client process to abort or the HTTP/2 session to be dropped. The vulnerability affects libsoup versions starting from 3.0.0 up to various patched versions including 3.0.7, 3.4.4, and 3.6.6 in specific Ubuntu builds.
Potential Impact
The vulnerability causes denial of service by aborting the client process or dropping the HTTP/2 session when interacting with a malicious HTTP/2 server under specific conditions. There is no impact on confidentiality or integrity, only availability is affected.
Mitigation Recommendations
A patch is available for this vulnerability. Users should upgrade to patched versions of libsoup 3 as indicated by the affected versions list. No additional mitigation steps are specified.
Technical Details
- Gcve Source
- db.gcve.eu
- Osv Id
- GHSA-qm5f-xr9c-mm27
- Osv Schema Version
- 1.4.0
- Aliases
- ["CVE-2026-85534"]
- Database Specific Severity
- MODERATE
- Cvss Version
- 3.1
- State
- PUBLISHED
Threat ID: 6a9ad4d6acd9273b49b66888
Added to database: 09/04/2026, 14:25:26 UTC
Last enriched: 10/18/2026, 02:23:25 UTC
Last updated: 10/18/2026, 18:48:24 UTC
Views: 50
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