CVE-2025-6338
Possible denial of service with multiple incoming connections to a Schannel based server with a TLS backend
There is an incomplete cleanup vulnerability in Qt Network's Schannel support on Windows which can lead to a Denial of Service over a long period.
This issue affects Qt from 5.15.0 through 6.8.3, from 6.9.0 before 6.9.2.
Attack profile
How easy it is to exploit
- Attack vector
- Network
- Complexity
- Low
- Privileges needed
- None
- User interaction
- None
What an attacker can affect
- Confidentiality
- None
- Integrity
- None
- Availability
- High
Exploit likelihood
What each source reports
CVE List Score used
Possible denial of service with multiple incoming connections to a Schannel based server with a TLS backend
There is an incomplete cleanup vulnerability in Qt Network's Schannel support on Windows which can lead to a Denial of Service over a long period.
This issue affects Qt from 5.15.0 through 6.8.3, from 6.9.0 before 6.9.2.
- Record
CVE-2025-6338- CVSS 4.0
- 9.2 Critical
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:H - Weakness
- CWE-459
- Updated
- 2026-11-02
EUVDEUVD-2025-34743
There is an incomplete cleanup vulnerability in Qt Network's Schannel support on Windows which can lead to a Denial of Service over a long period.
This issue affects Qt from 5.15.0 through 6.8.3, from 6.9.0 before 6.9.2.
- Record
EUVD-2025-34743- CVSS 4.0
- 9.2 Critical
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:H - Updated
- 2026-11-02
GitHub AdvisoriesGHSA-m4hj-jpxf-jhjp
There is an incomplete cleanup vulnerability in Qt Network's Schannel support on Windows which...
There is an incomplete cleanup vulnerability in Qt Network's Schannel support on Windows which can lead to a Denial of Service over a long period.This issue affects Qt from 5.15.0 through 6.8.3, from 6.9.0 before 6.9.2.
- Record
GHSA-m4hj-jpxf-jhjp- CVSS 4.0
- 9.2 Critical
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:H/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X - Weakness
- CWE-459
- Updated
- 2026-11-02
NVD
There is an incomplete cleanup vulnerability in Qt Network's Schannel support on Windows which can lead to a Denial of Service over a long period.
This issue affects Qt from 5.15.0 through 6.8.3, from 6.9.0 before 6.9.2.
- Record
CVE-2025-6338- CVSS 4.0
- 9.2 Critical
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:H/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X - Weakness
- CWE-459
- Updated
- 2026-11-02
Affected products
History
| Recorded | Changed | Sources |
|---|---|---|
| first indexed | CVE List, EUVD, GitHub Advisories, NVD |
Dates are when Every CVE recorded each change. Upstream dates may differ.
In short
CVE-2025-6338 is a critical vulnerability (CVSS 9.2) in Qt, published October 16, 2025. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.43%, the 37th percentile. No source names a fixed version.