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CVE-2025-21171VulnerabilityPublished Updated

CVE-2025-21171: Microsoft .NET 9.0 · Heap-based Buffer Overflow

Affects Microsoft .NET 9.0Source CVE Database V5

0

Not known to be exploited · CVSS 7.5 High · patch available : patch Microsoft .NET 9.0 soon.

Data as of 26 Oct 2026, 06:26 UTC

CVSS 3.1 base score
7.5High
How severe the flaw is on the 0–10 CVSS scale.
EPSS
1.7% chance of exploitation in 30 days – higher than 77% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch
Available
CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 14 Jan 2025

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponised: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  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), the Metasploit, Exploit-DB and nuclei-templates index as of 2026-10-26.

What to do

Affected software

ProductAffectedFixed in
Microsoft .NET 9.0Affected
  • 9.0.0
Fixed in–

AI-suggested

An official fix is available from Microsoft. Users and administrators should apply the provided security update for .NET 9.0 as soon as possible. Refer to the Microsoft advisory at https://msrc.microsoft.com/update-guide/vulnerability/CVE-2025-21171 for detailed patching instructions.

Description

.NET Remote Code Execution Vulnerability

References

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