CVE-2023-29336
CVE-2023-29336 is a security flaw in Microsoft Win32k, a part of Windows, Microsoft’s operating system. Someone who already has a foothold can use Microsoft Win32k 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 9 May 2023.[1]
Microsoft Win32k 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 10.0.10240.19926, 10.0.14393.5921, 6.0.6003.22070 and 6.1.7601.26519.
Description
CISA calls it a privilege escalation in Microsoft Win32k. In its words: “Microsoft Win32k contains an unspecified vulnerability that allows for privilege escalation up to SYSTEM privileges.”[1]
The underlying weakness is use after free (CWE-416), 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 10 Version 1507 | 10.0.10240.19926 |
| Windows 10 Version 1607 | 10.0.14393.5921 |
| Windows Server 2016 | 10.0.14393.5921 |
| Windows Server 2016 (Server Core installation) | 10.0.14393.5921 |
| Windows Server 2008 Service Pack 2 | 6.0.6003.22070 |
| Windows Server 2008 Service Pack 2 (Server Core installation) | 6.0.6003.22070 |
| Windows Server 2008 Service Pack 2 | 6.0.6003.22070 |
| Windows Server 2008 R2 Service Pack 1 | 6.1.7601.26519 |
Every device with Microsoft Win32k needs the update.
Exploitation
CISA added it to its catalog of known exploited vulnerabilities on 9 May 2023, 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 30 May 2023 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 41%. That’s in the top 2% 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 updates per vendor instructions.”[1]
- Update Microsoft Win32k 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 10.0.10240.19926 or later.Fixed in version 10.0.10240.19926, 10.0.14393.5921, 6.0.6003.22070 and 6.1.7601.26519. 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 41%.[4] |
See also
Other Microsoft Win32k flaws
- CVE-2016-0165: privilege escalation ·
- CVE-2015-2360: privilege escalation ·
- CVE-2018-8589: privilege escalation ·
- CVE-2014-4113: privilege escalation ·
- CVE-2021-41357: privilege escalation ·
- CVE-2021-40450: privilege escalation ·
Other Microsoft flaws
- CVE-2026-96951, Microsoft Windows: command injection ·
- CVE-2026-65660, Microsoft SharePoint: code injection ·
- CVE-2026-85880, Microsoft Windows: heap-based buffer overflow ·
- CVE-2026-81963, Microsoft Windows: link following ·
- CVE-2019-1068, Microsoft SQL Server: remote code execution ·
Other use after free flaws
- CVE-2026-109619, PHP: stale internal request-state ·
- CVE-2026-109618, PHP: memory corruption ·
- CVE-2020-9715, Adobe Acrobat: use-after-free ·
- CVE-2026-5281, Google Dawn: use-after-free ·
- CVE-2023-43000, Apple devices: use-after-free ·
Every Microsoft flaw on CISA’s list · Everything added in May 2023
References
- ^ Cybersecurity and Infrastructure Security Agency. “Microsoft Win32K Privilege Escalation Vulnerability”. Known Exploited Vulnerabilities Catalog, added 9 May 2023.
- ^ National Institute of Standards and Technology. “CVE-2023-29336 Detail”. National Vulnerability Database, published 9 May 2023.
- ^ Microsoft. Advisories and fixes: msrc.microsoft.com, msrc.microsoft.com.
- ^ FIRST. “Exploit Prediction Scoring System”. EPSS 0.412, percentile 98.7, 31 Oct 2026.
- CVE Program. “CVE-2023-29336”. 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.