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CVE Record

CVE-2026-42899: ASP.NET Core Denial of Service Vulnerability

Loop with unreachable exit condition ('infinite loop') in ASP.NET Core allows an unauthorized attacker to deny service over a network.

HighCVSS 7.5Not KEV-listedUpdated
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Glexia's TakeAutomated analysishigh

Security readout for executives and security teams

Plain-English summary

This is a high-severity ASP.NET Core denial-of-service issue. An unauthenticated attacker on the network may be able to trigger an infinite loop and make an affected service unavailable. The available sources indicate vendor patches exist, but do not show confirmed active exploitation.

Executive priority

Patch on the next urgent maintenance cycle, sooner for public or business-critical ASP.NET Core services. The main business risk is service outage, not data theft, based on the provided sources.

Technical view

CVE-2026-42899 is CWE-835 in ASP.NET Core: a loop with an unreachable exit condition. CVSS 3.1 is 7.5, with network attack vector, low complexity, no privileges, no user interaction, and high availability impact. The bundle lists .NET 8.0.0, 9.0.0, and 10.0.0 as affected.

Likely exposure

Exposure is most likely in internet-facing or network-reachable ASP.NET Core applications running the affected Microsoft .NET versions or downstream Red Hat-packaged builds referenced by Red Hat advisories.

Exploitation context

The source bundle marks KEV as false and CVSS exploit maturity as unproven. Treat this as a credible availability risk because it is unauthenticated and network-reachable, but do not assume active exploitation from the provided evidence.

Researcher notes

Evidence is sufficient for classification and triage, but limited on exact triggering conditions. Avoid assuming vulnerable code paths beyond ASP.NET Core on listed affected versions. No exploit steps or active exploitation claims are supported by the bundle.

Mitigation direction

  • Apply Microsoft’s vendor update for CVE-2026-42899 where applicable.
  • Apply relevant Red Hat errata for Red Hat-packaged .NET components.
  • Prioritize public ASP.NET Core services and critical internal APIs.
  • Use temporary traffic controls if patching exposed services is delayed.
  • Monitor vendor advisories for corrected package and runtime details.

Validation and detection

  • Inventory ASP.NET Core applications and installed .NET runtime versions.
  • Compare deployed versions against Microsoft and Red Hat advisories.
  • Confirm patched runtime or package versions after maintenance.
  • Review internet-facing routes for affected ASP.NET Core services.
  • Monitor service health for unexplained CPU saturation or availability drops.
Prepared
Confidence
high
Sources
10

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-835: 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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cve · low confidence lookup

CVE-2026-42899 mapping review

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

Open ATT&CK lookup
Vulnerability profileCVE Program record
Severity
High
CVSS
7.5 (3.1)
Known Exploited
No
Published

Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H/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
22Source links

SSVC decision data

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

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
7.5CVSS 3.1HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H/E:U/RL:O/RC:C3.93.6microsoft
7.5CVSS 3.1HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H3.93.6redhat-SADP

Vulnerability scoring details

Base CVSS 3.1 score

7.5High
CVSS 3.1 vector shape for CVE-2026-42899Attack VectorAttack ComplexityPrivileges RequiredUser InteractionScopeConfidentiality ImpactIntegrity ImpactAvailability Impact

Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H/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-SADPdotnet: .NET: infinite loop allows an attacker to cause a denial of service
other:Red Hat severity ratingcvssV3_1
  • 2026-05-12T18:02:35.031Z: Reported to Red Hat.
  • 2026-05-12T16:59:06.838Z: Made public.

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
Microsoft.NET 10.010.0.0Listed
Microsoft.NET 8.08.0.0Listed
Microsoft.NET 9.09.0.0Listed
Weakness

CWE details

CWE-835

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

CWE-835 · source CWE mapping

Loop with Unreachable Exit Condition ('Infinite Loop')

Loop with Unreachable Exit Condition ('Infinite Loop') represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.

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