Highest advisory severityHigh 2 vendors · 2 advisories

CVE-2026-108398: .NET Framework Security Feature Bypass Vulnerability

Not in the CISA KEV catalog. High advisory severity (CVSS 8.8, MS Server).

Compare the source-linked records below. Ratings and product/version details belong to each advisory; they are not a single CVE-wide score or proof that every listed product is affected. How VulniPulse collects and checks evidence.

NVD detail CVE.org

CVE-2026-108398 key facts

CISA KEV: Not listed (catalog checked Nov 6, 2026)
Highest advisory severity: High
CVSS base score: 8.8 (MS Server), 8.8 (Red Hat)
Weakness: CWE-426
Fixed releases: MS Server: KB5126868 (build 2.0.50727.8987 AND 3.0.30729.8982 AND 4.7.4150.0), KB5127666 (build 2.0.50727.9073 AND 3.0.30729.9070 AND 4.7.4150.0), KB5127685 (build 2.0.50727.9073 AND 3.0.30729.9070 AND 4.8.4811.0), KB5127683 (build 2.0.50727.9188 AND 3.0.30729.9171 AND 4.8.4811.0), KB5127687 (build 2.0.50727.9188 AND 3.0.30729.9171 AND 4.8.4811.0), KB5127667 (build 4.7.4150.0) and 2 more in the advisory
Vendor advisories: 2 from MS Server, Red Hat
VulniPulse record: Published Oct 13, 2026 · Updated Oct 24, 2026

Scores, vectors, weaknesses and fixed releases are quoted from vendor advisories that cover only CVE-2026-108398; bulletin-wide values are not repeated here.

Is CVE-2026-108398 exploited?

No exploitation is reported in the sources VulniPulse tracks: CVE-2026-108398 is not in the CISA KEV catalog (checked Nov 6, 2026) and no tracked advisory for it reports exploitation. That is not proof the vulnerability cannot be exploited.

How do I fix CVE-2026-108398?

Upgrade to a fixed release named by the vendor:

MS Server: KB5126868 (build 2.0.50727.8987 AND 3.0.30729.8982 AND 4.7.4150.0), KB5127666 (build 2.0.50727.9073 AND 3.0.30729.9070 AND 4.7.4150.0), KB5127685 (build 2.0.50727.9073 AND 3.0.30729.9070 AND 4.8.4811.0), KB5127683 (build 2.0.50727.9188 AND 3.0.30729.9171 AND 4.8.4811.0), KB5127687 (build 2.0.50727.9188 AND 3.0.30729.9171 AND 4.8.4811.0), KB5127667 (build 4.7.4150.0)

Install the applicable security update for your platform: KB5126868, KB5127666, KB5127685, KB5127683, KB5127687, KB5127667 (see the Microsoft Update Catalog). (MS Server)

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Vendor advisory comparison

MS Server

1 advisory

Advisory severityHigh8.8
High [CVE-2026-108398] .NET Framework Security Feature Bypass Vulnerability
CVE-2026-108398Source published Oct 13, 2026
.NET Framework Security Feature Bypass Vulnerability Affected products named by the advisory: Microsoft.NET Framework 3.5 AND 4.6.2/4.7/4.7.1/4.7.2 on Windows Server 2016; Microsoft.NET Framework 3.5 AND 4.6.2/4.7/4.7.1/4.7.2 on Windows Server 2019; Microsoft.NET Framework 3.5 AND 4.8 on Windows Server 2019; Microsoft.NET Framework 3.5 AND 4.8 on Windows Server 2022; and 4 more. Affected products named by the advisory: Microsoft .NET Framework 4.6.2/4.7/4.7.1/4.7.2 on Windows Server 2012 R2; Microsoft .NET Framework 4.8 on Windows Server 2012 R2.
Affected products in this advisory
Microsoft .NET Framework 3.5 AND 4.6.2/4.7/4.7.1/4.7.2 on Windows Server 2016
Microsoft .NET Framework 3.5 AND 4.6.2/4.7/4.7.1/4.7.2 on Windows Server 2019
Microsoft .NET Framework 3.5 AND 4.8 on Windows Server 2019
Microsoft .NET Framework 3.5 AND 4.8 on Windows Server 2022
2 more entries in the full advisory.
Source-reported affected versions
Affected-version details not available in this record.
Source-reported fixed versions
KB5126868 (build 2.0.50727.8987 AND 3.0.30729.8982 AND 4.7.4150.0)
KB5127666 (build 2.0.50727.9073 AND 3.0.30729.9070 AND 4.7.4150.0)
KB5127685 (build 2.0.50727.9073 AND 3.0.30729.9070 AND 4.8.4811.0)
KB5127683 (build 2.0.50727.9188 AND 3.0.30729.9171 AND 4.8.4811.0)
4 more entries in the full advisory.
Mitigation guidance
Install the applicable security update for your platform: KB5126868, KB5127666, KB5127685, KB5127683, KB5127687, KB5127667 (see the Microsoft Update Catalog).
Full advisory and evidence Open source bulletin

Red Hat

1 advisory

Advisory severityHigh8.8
High [CVE-2026-108398] .NET Framework: Security feature bypass via untrusted search path
CVE-2026-108398Source published Oct 13, 2026Source updated Oct 13, 2026
.NET Framework: Security feature bypass via untrusted search path. Red Hat rates this important (CVSS 8.8). Weakness: CWE-426. Affected product named by the advisory: Red Hat Hardened Images.
Related products — impact not confirmed
Red Hat Hardened Images
Source-reported affected versions
Affected-version details not available in this record.
Source-reported fixed versions
No fixed-version detail extracted. This does not mean no fix exists.
Mitigation guidance
No mitigation guidance extracted; consult the source.
Full advisory and evidence Open source bulletin

All MS Server advisories

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