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CVE Record

CVE-2026-40372: ASP.NET Core Elevation of Privilege Vulnerability

Improper verification of cryptographic signature in ASP.NET Core allows an unauthorized attacker to elevate privileges over a network.

CriticalCVSS 9.1Not KEV-listedUpdated
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Glexia's TakeAutomated analysiscritical

Security readout for executives and security teams

Plain-English summary

This is a critical Microsoft ASP.NET Core issue where signature verification can fail in a way that lets an unauthenticated remote attacker gain higher privileges. The sources identify patches, but the prompt bundle does not provide version-specific fixed builds. No cited source here confirms active exploitation.

Executive priority

Treat this as urgent patch work for affected Microsoft ASP.NET Core environments. The business concern is unauthorized privilege elevation over the network, but current provided evidence does not confirm exploitation in the wild.

Technical view

CVE-2026-40372 is CWE-347, improper verification of cryptographic signature, affecting ASP.NET Core 10.0 and Microsoft Visual Studio 2026 version 18.5. CVSS 3.1 is 9.1: network exploitable, low complexity, no privileges, no user interaction, with high confidentiality and integrity impact and no availability impact.

Likely exposure

Exposure is most likely where ASP.NET Core 10.0 is deployed or developed, especially network-reachable applications relying on affected signature validation paths. Visual Studio 2026 version 18.5 is also listed as affected. The provided evidence does not name downstream packages or hosted service configurations.

Exploitation context

The CVSS vector indicates remote, unauthenticated exploitation with low complexity and no user interaction. KEV is false, and the CVSS exploit maturity is unproven, so active exploitation should not be assumed from this bundle.

Researcher notes

Key evidence is vendor and CVE metadata: CWE-347, CVSS 9.1, affected Microsoft products, and MSRC patch reference. The bundle lacks root-cause detail, exploit conditions, fixed build numbers, and Red Hat impact details, so validation should stay vendor-guided.

Mitigation direction

  • Review the MSRC advisory for exact fixed versions and installation guidance.
  • Apply Microsoft updates for affected ASP.NET Core and Visual Studio versions.
  • Prioritize internet-facing ASP.NET Core 10.0 deployments for remediation.
  • Check Red Hat CVE and VEX entries for distribution-specific impact.
  • Monitor vendor advisories for updated exploit or workaround information.

Validation and detection

  • Inventory ASP.NET Core 10.0 deployments and Visual Studio 2026 18.5 installations.
  • Confirm installed versions against Microsoft’s fixed-version guidance.
  • Verify exposed ASP.NET Core services are included in patch tracking.
  • Review vulnerability scanner findings against the MSRC and Red Hat references.
  • Document exceptions where vendor guidance says a deployment is not affected.
Prepared
Confidence
medium
Sources
6

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

Conservative CVE-to-ATT&CK context

These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.

ATT&CK lookup starting points

Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.

cwe · low confidence lookup

CWE-347: Exact CWE lookup

Use the exact CWE identifier as the starting point before reviewing related ATT&CK behavior. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.

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description · low confidence lookup

Privilege behavior lookup

The CVE wording references privilege impact, so privilege escalation and authorization behavior review may help. This is a Glexia inferred lookup path, not an official MITRE, ATT&CK, or CVE Program mapping.

Open ATT&CK lookup
cve · low confidence lookup

CVE-2026-40372 mapping review

Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.

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Vulnerability profileCVE Program record
Severity
Critical
CVSS
9.1 (3.1)
Known Exploited
No
Published

Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N/E:U/RL:O/RC:C

Official CVE source material

CNA and ADP enrichment extracted from CVE v5

These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.

2CVSS vectors
5Timeline events
2ADP providers
5Source links

SSVC decision data

CISA-ADPCISA Coordinator
Timestamp
Version
2.0.3
Exploitation: noneAutomatable: yesTechnical Impact: total

CVSS vector scores

2 official scores

We collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.

ScoreVersionSeverityVectorExploitImpactSource
9.1CVSS 3.1CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N/E:U/RL:O/RC:C3.95.2microsoft
9.1CVSS 3.1CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N3.95.2redhat-SADP

Vulnerability scoring details

Base CVSS 3.1 score

9.1Critical
CVSS 3.1 vector shape for CVE-2026-40372Attack VectorAttack ComplexityPrivileges RequiredUser InteractionScopeConfidentiality ImpactIntegrity ImpactAvailability Impact

Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N/E:U/RL:O/RC:C

Attack Vector
NetworkAdjacentLocalPhysical
Attack Complexity
LowHigh
Privileges Required
NoneLowHigh
User Interaction
NoneRequired
Scope
ChangedUnchanged
Confidentiality Impact
HighLowNone
Integrity Impact
HighLowNone
Availability Impact
HighLowNone

Vulnerability timeline

Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.

  1. CVE reservedCVE Program

    The CVE ID was reserved by the assigning CNA.

  2. ADP timelineredhat-SADP

    Made public.

  3. CVE publishedCVE Program

    The CVE record was published.

  4. ADP timelineredhat-SADP

    Reported to Red Hat.

  5. CVE updatedCVE Program

    The CVE record metadata indicates this as the latest update time.

ADP provider summaries

CISA-ADPCISA ADP Vulnrichment
other:ssvc
redhat-SADPASP.NET Core: ASP.NET: ASP.NET Core: Privilege escalation via improper cryptographic signature verification
other:Red Hat severity ratingcvssV3_1
  • 2026-04-21T20:01:18.286Z: Reported to Red Hat.
  • 2026-04-21T19:20:50.215Z: Made public.

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
MicrosoftASP.NET Core 10.010.0Listed
MicrosoftMicrosoft Visual Studio 2026 version 18.518.5.0Listed
Weakness

CWE details

CWE-347

CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.

CWE-347 · source CWE mapping

Improper Verification of Cryptographic Signature

Improper Verification of Cryptographic Signature represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.

Open CWE intelligenceSame-CWE CVEs