CVE-2026-20839

Name: CVE-2026-20839
Creator: NVD / NIST
Published: 2026-01-13T18:16:12.32+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

MEDIUMCVSS 5.5/10EPSS 0.46%

Last modified Jun 17, 2026

CVE-2026-20839 is a medium-severity vulnerability rated 5.5/10 on the CVSS scale. Improper access control in Windows Client-Side Caching (CSC) Service allows an authorized attacker to disclose information locally.. EPSS estimates a 0.46% chance of exploitation in the next 30 days.

Description

Improper access control in Windows Client-Side Caching (CSC) Service allows an authorized attacker to disclose information locally.

Metrics

CVSS 3.1

5.5/10

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N

EPSS Probability

0.46%

36.7th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-284

Affected Software

Vendor	Product	Versions	Update
Microsoft	Windows 10 1607	< 10.0.14393.8783	—
Microsoft	Windows 10 1809	< 10.0.17763.8276	—
Microsoft	Windows 10 21h2	< 10.0.19044.6809	—
Microsoft	Windows 10 22h2	< 10.0.19045.6809	—
Microsoft	Windows 11 23h2	< 10.0.22631.6491	—
Microsoft	Windows 11 24h2	< 10.0.26100.7623	—
Microsoft	Windows 11 25h2	< 10.0.26200.7623	—
Microsoft	Windows Server 2008	r2	Sp1
Microsoft	Windows Server 2012	All versions	—
Microsoft	Windows Server 2012	r2	—
Microsoft	Windows Server 2016	< 10.0.14393.8783	—
Microsoft	Windows Server 2019	< 10.0.17763.8276	—
Microsoft	Windows Server 2022	< 10.0.20348.4648	—
Microsoft	Windows Server 2022 23h2	< 10.0.25398.2092	—
Microsoft	Windows Server 2025	< 10.0.26100.32230	—

References

https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-20839Vendor Advisory

Timeline

Published: Jan 13, 2026
Last Modified: Jun 17, 2026
Status: Analyzed

Frequently Asked Questions

What is CVE-2026-20839?

Improper access control in Windows Client-Side Caching (CSC) Service allows an authorized attacker to disclose information locally.

How severe is CVE-2026-20839?

CVE-2026-20839 has a CVSS score of 5.5/10 (MEDIUM severity). The EPSS model estimates a 0.46% probability of exploitation in the next 30 days.

How do I fix CVE-2026-20839?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

Are you affected by CVE-2026-20839?

Run a free Strix scan to check your systems for this vulnerability.

Scan your code now

Source: NVD / NIST