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VulnerabilityPublished Updated

CVE-2026-45584: Microsoft Malware Protection Engine · Heap-based Buffer Overflow

Affects Microsoft Malware Protection EngineSource CVE Database V5

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Not known to be exploited · CVSS 8.1 High : upgrade to 1.1.26040.8 soon.

Data as of 30 Oct 2026, 11:52 UTC

CVSS 3.1 base score
8.1High
How severe the flaw is on the 0–10 CVSS scale.
EPSS
0.8% chance of exploitation in 30 days – higher than 58% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch
Available – fixed in 1.1.26040.8
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 20 May 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponized: evidence found.

    Public exploit code: GitHub proofs of concept

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), GitHub proofs of concept, the Metasploit, Exploit-DB and nuclei-templates index as of 30 Oct 2026.

What to do

Upgrade Microsoft Malware Protection Engine to 1.1.26040.8.

Affected software

ProductAffectedFixed in
MicrosoftMicrosoft Malware Protection EngineAffected
  • >=1.1.0.0 <1.1.26040.8
Fixed in
  • 1.1.26040.8

AI-suggested

An official fix is available from Microsoft. Users and administrators should apply the security update provided by Microsoft for Microsoft Malware Protection Engine version 1.1.0.0 as soon as possible to mitigate this vulnerability.

Description

Heap-based buffer overflow in Microsoft Defender allows an unauthorized attacker to execute code over a network.

References

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