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Microsoft .NET CVE-2026-45491

| EUVDEUVD-2026-35675 MEDIUM
Improper Link Resolution Before File Access (CWE-59)
2026-06-09 secure@microsoft.com GHSA-7q4v-2mr6-5gpx
5.5
CVSS 3.1 · NVD
Temporal: 5.4
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Severity by source

NVD PRIMARY
5.5 MEDIUM
AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N
ENISA EUVD
HIGH
qualitative
CIRCL (temporal)
5.4 MEDIUM
cvss
SUSE
MEDIUM
qualitative
Red Hat
6.2 MEDIUM
qualitative

Primary rating from NVD.

CVSS VectorNVD

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N
Attack Vector
Local
Attack Complexity
Low
Privileges Required
Low
User Interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
High
Availability
None

Lifecycle Timeline

2
CVSS changed
Jun 18, 2026 - 03:38 NVD
6.2 (MEDIUM) 5.5 (MEDIUM)
Analysis Generated
Jun 09, 2026 - 19:43 vuln.today

DescriptionNVD

Improper link resolution before file access ('link following') in .NET allows an unauthorized attacker to perform tampering locally.

AnalysisAI

Local file tampering via symlink/junction following in Microsoft .NET runtimes 8.0, 9.0, and 10.0 allows a local unauthenticated attacker to redirect file operations to unintended targets, achieving high-integrity impact without requiring elevated privileges. The vulnerability stems from improper link resolution (CWE-59) before file access, enabling unauthorized modification of files the attacker would otherwise lack write access to. No public exploit identified at time of analysis and no CISA KEV listing, but the low attack complexity (AC:L) and absence of privilege requirements (PR:N) make exploitation straightforward for any actor with local access.

Technical ContextAI

CWE-59 (Improper Link Resolution Before File Access - 'Link Following') describes a class of vulnerabilities where an application resolves symbolic links, hard links, or OS junction points to a target path without adequately validating whether the resolved target is the intended one. In Windows and Linux environments, attackers can create symlinks or directory junctions that redirect .NET runtime file I/O to privileged or sensitive paths. The .NET runtime versions 8.0.0-8.0.27, 9.0.0-9.0.16, and 10.0.0-10.0.8 are confirmed affected per ENISA EUVD-2026-35675. The attack vector being local (AV:L) means the runtime's file handling code does not perform sufficient time-of-check to time-of-use (TOCTOU) or link target validation, allowing a race or pre-planted link to subvert expected access control decisions. The tag 'Authentication Bypass' from the intelligence source suggests the link-following behavior may circumvent OS-level access controls during .NET file operations.

RemediationAI

Upgrade to the vendor-released patched versions: .NET 8.0.28, .NET 9.0.17, or .NET 10.0.9, as applicable. The MSRC advisory at https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-45491 provides official guidance and patch download links. For systems where immediate patching is not feasible, restrict local interactive and service account access to the minimum necessary - this directly limits the pool of potential attackers given the local attack vector requirement. Additionally, auditing and restricting write permissions to directories where .NET applications perform file I/O can reduce the opportunity for symlink planting. Note that compensating controls do not eliminate the vulnerability and carry operational trade-offs including potential breakage of legitimate application workflows that rely on symlinked paths.

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Vendor StatusVendor

SUSE

Severity: Moderate
Product Status
SUSE Liberty Linux 10 Fixed
SUSE Liberty Linux 8 Fixed
SUSE Liberty Linux 9 Fixed

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CVE-2026-45491 vulnerability details – vuln.today

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