CVE-2026-21218 | .NET Spoofing Vulnerability

Improper handling of missing special element in .NET allows an unauthorized attacker to perform spoofing over a network.

Published: 2026-02-10 Last update: 2026-02-12 Assigner: [email protected] Source: [email protected]
NVD Status：Analyzed，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2026-21218 is rated Moderate Risk (51.5/100): CVSS High severity, with medium exploitation likelihood (EPSS 1.01%). Review affected assets and schedule remediation.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Exploit prediction scoring system (EPSS) score for CVE-2026-21218

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-06-15 0.06% 1.01% +0.96%
2 2026-06-12 0.04% 0.06% +0.01%
3 2026-02-11 — 0.04% —

Full EPSS history (3 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2026-21218

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
7.5 3.1 HIGH
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:N)
Doesn’t really leak secrets in a meaningful way.
Integrity (I:H)
They could widely tamper with or forge data—trust in the data is badly hurt.
Availability (A:N)
Service keeps running; no real outage angle.
 3.9 3.6 [email protected]

Weakness enumeration for CVE-2026-21218

GitHub Security Advisory for CVE-2026-21218

GHSA-qvhc-9v3j-5rfw · Severity: high · Ecosystem: nuget — Microsoft Security Advisory CVE-2026-21218 | .NET Security Feature Bypass Vulnerability

OS Trackers for CVE-2026-21218

vendor priority summary link
alpine — CVE-2026-21218: 3 source package rows (dotnet10-runtime, dotnet8-runtime, dotnet9-runtime); 6 state rows across 2 repos (3.23-community, edge-community); fixed 6, open 0. https://security.alpinelinux.org/vuln/CVE-2026-21218
ubuntu medium CVE-2026-21218 medium priority: Ubuntu including 5 source packages (dotnet10, dotnet6, dotnet7, dotnet8, dotnet9), 42 status rows across 9 suites (bionic, focal, jammy, noble, plucky, questing, trusty, upstream, xenial): DNE 29, released 9, needs-triage 2, deferred 1, ignored 1. https://ubuntu.com/security/CVE-2026-21218

Affected software / configurations for CVE-2026-21218

Vendor Product Version Raw CPE
microsoft .net >= 8.0.0, < 8.0.24 cpe:2.3:a:microsoft:.net:*:*:*:*:*:*:*:*
microsoft .net >= 9.0.0, < 9.0.13 cpe:2.3:a:microsoft:.net:*:*:*:*:*:*:*:*
microsoft .net >= 10.0.0, < 10.0.3 cpe:2.3:a:microsoft:.net:*:*:*:*:*:*:*:*

References for CVE-2026-21218

cvelogic Threat Intelligence