CVE-2021-42292
CVE-2021-42292 is a security flaw in Microsoft Office, part of Microsoft Office. Someone who already has a way in can use Microsoft Office to run their own code. The US Cybersecurity and Infrastructure Security Agency (CISA) added it to its catalog of flaws known to be used in attacks on 17 Nov 2021.[1]
Microsoft Office 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 https://aka.ms/OfficeSecurityReleases, 15.0.5397.1001, 16.0.5239.1001 and 16.55.21111400.
Description
CISA calls it an excel security feature bypass in Microsoft Office. In its words: “A security feature bypass vulnerability in Microsoft Excel would allow a local user to perform arbitrary code execution.”[1]
The underlying weakness is CWE-357, 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 |
|---|---|
| Microsoft 365 Apps for Enterprise | https://aka.ms/OfficeSecurityReleases |
| Microsoft Excel 2013 Service Pack 1 | 15.0.5397.1001 |
| Microsoft Excel 2016 | 16.0.5239.1001 |
| Microsoft Office 2013 Service Pack 1 | 15.0.5397.1001 |
| Microsoft Office 2016 | 16.0.5239.1001 |
| Microsoft Office 2019 | https://aka.ms/OfficeSecurityReleases |
| Microsoft Office 2019 for Mac | 16.55.21111400 |
| Microsoft Office LTSC 2021 | https://aka.ms/OfficeSecurityReleases |
Every device with Microsoft Office needs the update.
Exploitation
CISA added it to its catalog of known exploited vulnerabilities on 17 Nov 2021, 7 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 1 Dec 2021 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 43%. 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 Office 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 https://aka.ms/OfficeSecurityReleases or later.Fixed in version https://aka.ms/OfficeSecurityReleases, 15.0.5397.1001, 16.0.5239.1001 and 16.55.21111400. 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 43%.[4] |
See also
Other Microsoft Office flaws
- CVE-2009-0238: remote code execution ·
- CVE-2026-21514: word reliance on untrusted inputs in a security decision ·
- CVE-2026-21509: security feature bypass ·
- CVE-2009-0556: powerPoint code injection ·
- CVE-2007-0671: excel remote code execution ·
- CVE-2023-23397: outlook 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 ·
Added the same day
- CVE-2021-42321, Microsoft Exchange: server remote code execution ·
- CVE-2021-40449, Microsoft Windows: win32k privilege escalation ·
- CVE-2021-22204, Perl Exiftool: remote code execution ·
Every Microsoft flaw on CISA’s list · Everything added in November 2021
References
- ^ Cybersecurity and Infrastructure Security Agency. “Microsoft Excel Security Feature Bypass”. Known Exploited Vulnerabilities Catalog, added 17 Nov 2021.
- ^ National Institute of Standards and Technology. “CVE-2021-42292 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 0.430, percentile 98.7, 31 Oct 2026.
- CVE Program. “CVE-2021-42292”. 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.