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Vulnerabilities/CVE-2026-33819Public Intelligence Dossier
Source: microsoft · Limited verification•Last verified: •Collection Degraded
CVE-2026-33819Unknown / EvaluatingCRITICAL (raw)CVSS 10.0CWE-502

Deserialization of untrusted data in Microsoft Bing allows an unauthorized attacker to execute code over a network.

Published: 24 Apr 2026•Last updated: 27 Oct 2026, 02:40 AM IST•Source identifier: secure@microsoft.com
Dossier completeness: source-provided sections 2 / 3 · rule guidance available. Missing source facts count as incomplete.
Official source
CISA KEV catalog
Unknown
KEV status was not determined.
CVSS score
10.0CRITICAL (raw)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H
Metric sourcesecure@microsoft.com
EPSS probability
0.8%0.008
Percentile58th
Weakness type
CWE-502
No further CWE recorded
Remediation
Patch status unknown
No fixed version or KB recorded

Why It Matters

Analysis dossier

Why It Matters

Deserialization of untrusted data in Microsoft Bing allows an unauthorized attacker to execute code over a network.

SOC priority

High Severity / Review

Actively exploited (source statement)

Unknown

Publicly disclosed

Unknown

Risk basis: Microsoft or Microsoft-managed product relevance; CRITICAL severity; Critical source severity without confirmed exploitation

Affected Products & Remediation

1 source-backed product
Affected products and versions (source)
  • microsoft bing · version range not provided by source · NVD CPE · Source
Recorded patch / KBNot provided by source

Vendor or catalog guidance (source)

Not provided by source

Known exploitation (source facts)

Only what a source states. Unknown means no source has said either way; it is not "not exploited".

CISA KEV
Unknown
Exploited (source statement)
Unknown
Publicly disclosed (source)
Unknown

Suggested hunting (rule-based inference)

SecOps Signal recommendation (rule-based inference). These steps are hunting hypotheses from the vulnerability class; they do not state or imply that exploitation occurred here or anywhere.

Matched deserialization (CWE-502); network-unauthenticated (CVSS AV:N, CVSS PR:N, CVSS UI:N)

Exposure

  1. Find installations of the affected component and confirm the source-stated version range.Telemetry: Application inventory · Deserialization risk requires component and version evidence. · Rule deserialization
  2. Identify devices reporting this CVE and note which expose the affected service to untrusted networks.Telemetry: DeviceTvmSoftwareVulnerabilities · A network-reachable, no-privilege vector makes internet-facing instances the first exposure question. · Rule network-unauthenticated

Exploitation evidence

  1. Review unusual child processes or network connections from the affected service.Telemetry: DeviceProcessEvents · Unexpected behavior may support investigation but is not proof by itself. · Rule deserialization
Show more (2)

Exploitation evidence

  1. Review inbound connections to the affected service from unexpected sources since the advisory date.Telemetry: DeviceNetworkEvents · Hunting hypothesis from the CVSS vector; it does not show that exploitation occurred. · Rule network-unauthenticated

Response

  1. Verify the vendor update or mitigation on each affected installation.Telemetry: Application change records · Response must follow the authoritative source guidance. · Rule deserialization

CISA KEV Record

CISA KEV status was not determined for this record.

Change History & Source Data

— No recorded material change

CNA / source
secure@microsoft.com
Record status · verification
UPDATED · Microsoft primary source linked
CPE
cpe:2.3:a:microsoft:bing:-:*:*:*:*:*:*:*

Evidence & Provenance

2 public sources
msrc.microsoft.comSource recordnvd.nist.govSource record

Linked by the query's stored exact CVE association. Review required tables and validation status before use.

Detection Hunting Query
Target: DeviceTvmSoftwareVulnerabilities•Defender XDR
Detect endpoints exposed to CVE-2026-33819
Purpose: Exposure assessment (Category: Exposure Check)Why linked: Query metadata names CVE-2026-33819
DeviceTvmSoftwareVulnerabilities| where CveId == "CVE-2026-33819"| project DeviceId, DeviceName, OSPlatform, OSVersion, SoftwareVendor, SoftwareName, SoftwareVersion, CveId, VulnerabilitySeverityLevel, RecommendedSecurityUpdate, RecommendedSecurityUpdateId| sort by VulnerabilitySeverityLevel desc
Schema Checked · Not runtime validatedSource: SecOps Signal deterministic template · Limited verificationStatic screening: Passed structure and schema checks; tenant execution is not verified.
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Correlated briefings

SecOps Signal surfaces public advisory facts only. A missing value means the source has not published it, not that your environment is unaffected. No tenant inventory is connected.