CVE-2026-81963
CVE-2026-81963 is a security flaw in Microsoft Windows, Microsoft’s operating system for PCs and servers. Someone who already has a foothold can use Microsoft Windows to take full control of the machine. The US Cybersecurity and Infrastructure Security Agency (CISA) added it to its catalog of flaws known to be used in attacks on 8 Sep 2026.[1]
Microsoft Windows is in things households have, such as phones, computers, browsers and everyday apps, so the fix matters at home as much as at work. Fixed in version 10.0.22631.7582, 10.0.26100.9445, 10.0.26200.9445 and 10.0.28000.2954 and others.
Description
CISA calls it a link following in Microsoft Windows. In its words: “Microsoft Windows Update Stack contains a link following vulnerability that allows a local attacker to escalate privileges locally up to SYSTEM.”[1]
The underlying weakness is CWE-59, improper access control (CWE-284), in MITRE’s list of common software weaknesses.[2]
It scores 7.8 out of 10 on the Common Vulnerability Scoring System, which rates it high, scored by the organisation that published the CVE using CVSS 3.1.[2]
Affected versions
NVD’s record lists these fixed versions: in each line, everything before the version shown is affected.[2]
| Product | Fixed in |
|---|---|
| Windows 11 version 23H2 | 10.0.22631.7582 |
| Windows 11 Version 23H2 | 10.0.22631.7582 |
| Windows 11 Version 24H2 | 10.0.26100.9445 |
| Windows 11 Version 25H2 | 10.0.26200.9445 |
| Windows 11 version 26H1 | 10.0.28000.2954 |
| Windows Server 2025 | 10.0.26100.33438 |
| Windows Server 2025 (Server Core installation) | 10.0.26100.33438 |
Every device with Microsoft Windows needs the update.
Exploitation
CISA added it to its catalog of known exploited vulnerabilities on 8 Sep 2026, within a day of it being made public. CISA lists a flaw only when it has reliable evidence of it being exploited, and gave US federal agencies until 22 Sep 2026 to fix it.[1]
FIRST’s Exploit Prediction Scoring System, which estimates how likely a flaw is to be used in attacks in the next 30 days from what it sees across the internet, puts it at under 1%. That’s in the top 67% of the flaws it scores.[4]
CISA assesses it as not automatable: each attack takes some work.
CISA doesn’t say who was attacked, or how.
Fix
Microsoft has published a fix or advice.[3] CISA’s required action: “Apply mitigations in accordance with vendor instructions, ensuring compliance with CISA’s BOD 26-04 Prioritizing Security Updates Based on Risk (see URL in Notes) guidance and CISA’s “Forensics Triage Requirements” (see URL in Notes).”[1]
- Update Microsoft Windows now.On Windows: Settings, Windows Update, Check for updates, then restart. Office updates come the same way, or from any Office app: File, Account, Update Options. Then turn on automatic updates, so the next fix arrives on its own.
- Check you’re on 10.0.22631.7582 or later.Fixed in version 10.0.22631.7582, 10.0.26100.9445, 10.0.26200.9445 and 10.0.28000.2954 and others. Anything older is what attackers are going after.
- If there’s no update, stop using it.CISA’s advice when a flaw being used in attacks has no fix is to stop using the product until it does.
Timeline
| Date | Event |
|---|---|
| The flaw is made public in the National Vulnerability Database, with a severity score of 7.8.[2] | |
| CISA adds it to its catalog of flaws known to be used in attacks.[1] | |
| CISA’s deadline for US government agencies to fix it.[1] | |
| FIRST puts the odds of it being used in attacks in the next 30 days at under 1%.[4] |
See also
Other Microsoft Windows flaws
- CVE-2026-96951: command injection ·
- CVE-2026-85880: heap-based buffer overflow ·
- CVE-2008-4250: buffer overflow ·
- CVE-2026-32202: protection mechanism failure ·
- CVE-2025-60710: link following ·
- CVE-2023-36424: out-of-bounds read ·
Similar flaws
- CVE-2015-5287, Red Hat Automatic Bug Reporting Tool: privilege escalation ·
- CVE-2025-48384, Git: link following ·
Added the same day
- CVE-2026-86218, N-able N-central: static code injection ·
- CVE-2026-85880, Microsoft Windows: heap-based buffer overflow ·
- CVE-2026-75650, Adobe Commerce and Magento: improper neutralization of special elements used in a template engine ·
Every Microsoft flaw on CISA’s list · Everything added in September 2026
References
- ^ Cybersecurity and Infrastructure Security Agency. “Microsoft Windows Link Following Vulnerability”. Known Exploited Vulnerabilities Catalog, added 8 Sep 2026.
- ^ National Institute of Standards and Technology. “CVE-2026-81963 Detail”. National Vulnerability Database, published 8 Sep 2026.
- ^ Microsoft. Advisories and fixes: msrc.microsoft.com, msrc.microsoft.com.
- ^ FIRST. “Exploit Prediction Scoring System”. EPSS 0.004, percentile 33.5, 31 Oct 2026.
- CVE Program. “CVE-2026-81963”. The official CVE record.
This article is built from CISA’s catalog (version 2026.10.30), NVD’s record and FIRST’s scores, kept in HARD’s database and checked every morning. The plain English is HARD’s.