CVE-2026-55011: Integer underflow (wrap or wraparound) in Microsoft Defender allows an unauthorized attacker to execute code l

Q: How do I fix CVE-2026-55011?

malware protection engine: upgrade to 1.1.26060.3008. Exact commands for each OS are on this page.

Q: Is CVE-2026-55011 being exploited?

CVE-2026-55011 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2026-55011 affect?

CVE-2026-55011 affects malware protection engine. Severity is high (CVSS 7.8). Integer underflow (wrap or wraparound) in Microsoft Defender allows an unauthorized attacker to execute code locally.

Q: How urgent is CVE-2026-55011?

Priority 42/100. High severity; On your watchlist

This month

HIGH 7.8WATCHLISTUPGRADE

CVE-2026-55011 is a high-severity flaw (CVSS 7.8) affecting malware protection engine. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Integer underflow (wrap or wraparound) in Microsoft Defender allows an unauthorized attacker to execute code locally.

Why this priority

High severity
On your watchlist

A fixed release or distro patch exists.

Risk facts

CVSS score	7.8 (High)
Attack vector	Local
Attack complexity	Low
Privileges needed	None
User interaction	Required
EPSS exploit chance	0.5% (top 61%)
CISA exploited list	No
Weakness	CWE-191
Published	2026-07-14
Last modified	2026-10-24

Publisher (CNA): Microsoft Corporation · Vendor: microsoft

Last updated 2026-10-24 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-07-14 17:17 UTCPublished CVE record published
2026-10-24 21:10 UTCUpdated Record last modified

microsoft malware protection engine UPGRADE

Affected: < 1.1.26060.3008

Fixed in: 1.1.26060.3008

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy malware-protection-engine || rpm -q malware-protection-engine || malware-protection-engine --version

2. UPGRADE to 1.1.26060.3008 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade malware-protection-engine

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade malware-protection-engine

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2026-55011?

malware protection engine: upgrade to 1.1.26060.3008. Exact commands for each OS are on this page.

Is CVE-2026-55011 being exploited?

CVE-2026-55011 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2026-55011 affect?

CVE-2026-55011 affects malware protection engine. Severity is high (CVSS 7.8). Integer underflow (wrap or wraparound) in Microsoft Defender allows an unauthorized attacker to execute code locally.

How urgent is CVE-2026-55011?

Priority 42/100. High severity; On your watchlist

Software pages

Windows Defender vulnerabilities

Related CVEs

CVE-2026-55012 HIGH 7.8 UPGRADE Integer overflow or wraparound in Microsoft Defender allows an unauthorized attacker to execute code locally.

References

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