CVE-2021-41379
CVE-2021-41379 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 3 Mar 2022, and says ransomware gangs have used it.[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 10.0.10240.19119, 10.0.14393.4770, 10.0.17763.2300 and 10.0.18363.1916 and others.
Description
CISA calls it an installer privilege escalation in Microsoft Windows. In its words: “Microsoft Windows Installer contains an unspecified vulnerability that allows for privilege escalation.”[1]
The underlying weakness is CWE-1386, in MITRE’s list of common software weaknesses.[2]
It scores 5.5 out of 10 on the Common Vulnerability Scoring System, which rates it medium, 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 | 10.0.10240.19119 |
| Windows 10 Version 1607 | 10.0.14393.4770 |
| Windows 10 Version 1809 | 10.0.17763.2300 |
| Windows 10 Version 1909 | 10.0.18363.1916 |
| Windows 10 Version 2004 | 10.0.19041.1348 |
| Windows 10 Version 20H2 | 10.0.19042.1348 |
| Windows 10 Version 21H1 | 10.0.19043.1348 |
| Windows 11 version 21H2 | 10.0.22000.318 |
Every device with Microsoft Windows needs the update.
Exploitation
CISA added it to its catalog of known exploited vulnerabilities on 3 Mar 2022, 113 days after it was made public. CISA lists a flaw only when it has reliable evidence of it being exploited, and gave US federal agencies until 17 Mar 2022 to fix it.[1] CISA says ransomware gangs have used it.
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 19%. That’s in the top 3% 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 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 10.0.10240.19119 or later.Fixed in version 10.0.10240.19119, 10.0.14393.4770, 10.0.17763.2300 and 10.0.18363.1916 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 5.5.[2] | |
| CISA adds it to its catalog of flaws known to be used in attacks, noting that ransomware gangs have used it.[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 19%.[4] |
See also
Other Microsoft Windows flaws
- CVE-2026-96951: command injection ·
- CVE-2026-85880: heap-based buffer overflow ·
- CVE-2026-81963: link following ·
- CVE-2008-4250: buffer overflow ·
- CVE-2026-32202: protection mechanism failure ·
- CVE-2025-60710: link following ·
Added the same day
- CVE-2022-20708, Cisco Small Business RV160, RV260, RV340, and RV345 Series Routers: small business RV series routers stack-based buffer overflow ·
- CVE-2022-20703, Cisco Small Business RV160, RV260, RV340, and RV345 Series Routers: small business RV series routers stack-based buffer overflow ·
- CVE-2022-20701, Cisco Small Business RV160, RV260, RV340, and RV345 Series Routers: small business RV series routers stack-based buffer overflow ·
- CVE-2022-20700, Cisco Small Business RV160, RV260, RV340, and RV345 Series Routers: small business RV series routers stack-based buffer overflow ·
- CVE-2022-20699, Cisco Small Business RV160, RV260, RV340, and RV345 Series Routers: small business RV series routers stack-based buffer overflow ·
Every Microsoft flaw on CISA’s list · Everything added in March 2022
References
- ^ Cybersecurity and Infrastructure Security Agency. “Microsoft Windows Installer Privilege Escalation Vulnerability”. Known Exploited Vulnerabilities Catalog, added 3 Mar 2022.
- ^ National Institute of Standards and Technology. “CVE-2021-41379 Detail”. National Vulnerability Database, published 10 Nov 2021.
- ^ Microsoft. Advisories and fixes: msrc.microsoft.com, portal.msrc.microsoft.com.
- ^ FIRST. “Exploit Prediction Scoring System”. EPSS 0.195, percentile 97.4, 31 Oct 2026.
- CVE Program. “CVE-2021-41379”. 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.