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CVE-2025-6338

Possible denial of service with multiple incoming connections to a Schannel based server with a TLS backend

Critical9.2EPSS 0.43%
Published
Updated
Reserved
Assigned by
TQtC

Description

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.

Scores

CVSS scores of CVE-2025-6338, by who scored it
Scored byCVSSScoreVector
TQtCCNA (assigner)4.0Critical9.2CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:H
NVDNVD · Deferred4.0Critical9.2CVSS: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
EPSS (exploitation in 30 days)
0.43% · top 63% of all CVEs (6 Nov 2026)
CISA SSVC
Exploitation: none · Automatable: yes · Technical impact: partial
Loading the EPSS history…

The list uses the assigner's score when there is one, then CISA's, then NVD's: Critical 9.2.

Weakness

Affected products

  • Qt · Qt

    • unaffected < 5.15.0
    • affected 5.15.0 – ≤ 6.8.3
    • unaffected 6.8.4 – < 6.9.0
    • affected 6.9.0 – < 6.9.2

References (1)

Sources

The same CVE in the primary databases and aggregators, to check against.

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Record last updated .