CVE-2025-62455: Local Privilege Escalation in Microsoft Message Queuing (MSMQ)

Microsoft has published an advisory for CVE-2025-62455, a newly recorded elevation-of-privilege vulnerability in Microsoft Message Queuing (MSMQ) that affects installations where the MSMQ component is present and accessible; the vendor entry confirms the vulnerability identifier but offers only a brief description and no low‑level exploit details, while third‑party vulnerability aggregators report a CVSS v3.1 base score of 7.8 (High) and characterize the flaw as improper input validation that allows an authorized local attacker to gain elevated privileges.

Background / Overview​

Microsoft Message Queuing (MSMQ) is a legacy but widely deployed Windows component that provides durable, asynchronous message delivery for distributed applications. Administrators often install MSMQ to support enterprise or line‑of‑business software where guaranteed delivery and decoupling are required. Because MSMQ runs with elevated privileges on hosts where it is installed, security issues in its implementation have historically carried outsized operational impact. Past MSMQ bugs have ranged from denial‑of‑service issues to privilege escalations and, in rare cases, remote code execution—so any new MSMQ advisory warrants expedited triage. CVE-2025-62455 is described in vendor metadata as an improper input validation weakness (mapped to CWE‑20). Aggregators list the attack vector as Local (not remotely exploitable), with Privileges Required: Low, and impacts to confidentiality, integrity and availability rated high in the CVSS vector reported by external trackers. That combination indicates an attack that starts from a non‑privileged local process or user account and seeks to escalate to SYSTEM or similar high privilege on a machine that has MSMQ enabled. Note: Microsoft’s Update Guide entry is intentionally concise; in such cases the vendor typically confirms the CVE and provides remediation mapping but withholds technical exploit details until fixes are widely deployed to avoid rapid weaponization. Treat public summaries with caution until vendor patches and KB mappings are available for your specific OS builds.

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What we can verify right now​

• Microsoft has an advisory entry for CVE‑2025‑62455 in its Security Update Guide; the entry confirms the vulnerability exists but includes minimal public technical detail.
• Third‑party vulnerability aggregators report a CVSS v3.1 base score of 7.8 (High) with vector metrics that imply a local attack requiring low privileges and no user interaction. These aggregators describe the underlying issue as improper input validation in the Message Queuing component.
• Public disclosure timing: the CVE record and third‑party entries show the report as added on or about December 9, 2025, which aligns with the vendor advisory entry timestamp seen in the trackers. This is a recent disclosure and should be prioritized for triage.

These facts are corroborated by multiple public trackers and the vendor’s advisory metadata. However, at the time of writing there is no authoritative public proof‑of‑concept (PoC) code available from either the vendor or major research groups, and there are no confirmed wide‑scale exploitation reports tied specifically to CVE‑2025‑62455 in public telemetry feeds. That absence is not proof of safety—targeted attackers often keep exploits private—so defenders should assume a conservative posture until patches are applied.

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Why this matters for Windows administrators and enterprises​

MSMQ often runs on servers and services that support mission‑critical workflows (financial processing, order queuing, integration between applications). Because the MSMQ service is frequently installed with elevated privileges and because it interacts with inter‑process and networked clients, a successful local elevation‑of‑privilege can allow an attacker who already has a foothold (for example, through a compromised user account or malicious software running as a standard user) to gain SYSTEM privileges and take full control of the host.
Key reasons this CVE demands attention:

• Low barrier to impact in post‑compromise scenarios — an attacker who can execute as a local standard user may be able to exploit MSMQ to escalate privileges. Mitigation must therefore consider hosts where any untrusted code can run.
• Operational blast radius — servers with MSMQ installed can be central to distributed processing; disruption or takeover can cascade to multiple applications. Historical coverage of MSMQ issues shows real operational impact when unattended services are exploited.
• Common presence in enterprise estates — while MSMQ is optional, it remains present across many legacy and specialized application stacks; discovery and inventory are nontrivial but essential first steps.

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Technical snapshot (what the public data says)​

• Vulnerability class: Improper Input Validation (CWE‑20) in the Message Queuing component. Public trackers map the CVE to that weakness class, indicating the service may accept and act on malformed or insufficiently validated data.
• Attack vector: Local. Aggregated vectors suggest the vulnerability is not exploitable remotely without prior local access. The high confidentiality/integrity/availability impacts in the CVSS vector imply successful exploitation allows elevated rights with system‑level consequences.
• Privileges required: Low (a non‑privileged local account or process). If accurate, this makes the bug a practical lateral‑movement / privilege‑chain primitive for adversaries who can achieve initial code execution at user level.
• Public details: Minimal. Microsoft’s advisory confirms the identifier and impact class but omits exploit recipes and low‑level internals. Defenders should rely on the vendor’s patches and authoritative KBs rather than speculative PoCs.

Warning: Some aggregators sometimes extrapolate vector strings or CVSS components when vendor data is sparse; verify the exact CVSS vector and affected product mapping on Microsoft’s Update Guide/KBs once Microsoft publishes the associated KB updates for your OS SKUs. Until then, treat external CVSS entries as useful early indicators rather than definitive authority.

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Immediate action checklist (for Windows admins) — short, prioritized steps​

• Identify hosts with MSMQ installed. Use Server Manager, Add/Remove Windows Features inventories, or configuration management queries to find machines where Message Queuing is present.
• Apply vendor updates immediately once Microsoft publishes the KB matching your Windows builds. Track the Microsoft Security Update Guide entry for this CVE for KB mapping, and use WSUS / SCCM / Intune to deploy to production following normal test/validate steps.
• If you cannot patch immediately, implement temporary mitigations:
• Disable the MSMQ feature on systems that do not need it.
• Restrict access to MSMQ only to trusted administrative and application subnets via host and network firewalls.
• Restrict which accounts and services may interact with MSMQ queues and set queue permissions to least privilege.
• Hunt for indicators of compromise on MSMQ hosts: review process execution (services running as SYSTEM), event logs showing unusual MSMQ errors/crashes, and any local process launches initiated by mqsvc.exe or related components. Increase monitoring for post‑compromise behaviors like persistence, credential access, or scheduled tasks.
• Prepare for incident response: ensure backups, forensic capture procedures, and containment plans are ready for affected hosts; assume a compromised host might require rebuild if exploitation is confirmed.

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Recommended mitigations — detailed steps​

• Patch Management: Prioritize installing Microsoft updates that map to CVE‑2025‑62455. For large estates, stage according to risk: internet‑facing or administrative hosts with MSMQ installed first, then application servers, followed by endpoints. Ensure reboots are scheduled when required.
• Disable Unused MSMQ: On systems where MSMQ provides no operational value, remove the Windows feature. This permanently removes the attack surface for this component. For Windows Server, use Server Manager or PowerShell (Remove‑WindowsFeature / Disable‑WindowsOptionalFeature). Confirm dependency chains before removal.
• Network Isolation: Block untrusted network segments from reaching MSMQ hosts. Implement host firewall rules limiting inbound connections to only known management and application nodes. Network ACLs and segmentation reduce lateral movement options for attackers.
• Harden Queue Permissions: Review and tighten MSMQ queue ACLs so only specific service accounts and administrative users can send/receive messages, create queues, or modify queue properties. Principle of least privilege reduces exploit utility.
• Monitoring and Logging: Ensure MSMQ‑related events are forwarded to your SIEM, and add detections for abnormal queue creation, sudden large queue sizes, and service crashes. Instrument host EDR to alert on suspicious child processes spawned by the MSMQ service process.

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Detection and hunting guidance​

When hunting for exploitation attempts targeting MSMQ, focus on:

• Unusual local process spawn events where non‑standard processes are created by MSMQ service processes or by services running with SYSTEM privileges.
• Sudden message queue errors, repeated crashes of the MSMQ service, or unexpected queue creation/deletion.
• New scheduled tasks, service registrations, or binary drops coinciding with MSMQ instability.
• Lateral movement patterns originating from a host with MSMQ installed where a user‑level compromise precedes privilege escalation activity.

If you detect signs of successful privilege escalation, treat the host as compromised: isolate from network, preserve memory and disk images for forensic analysis, and follow incident response playbooks. Assume the attacker may have had SYSTEM context and therefore broad access to credentials and persisted artifacts.

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Risk analysis — strengths, weaknesses, and practical exploitation likelihood​

Strengths of Microsoft’s approach:

• Microsoft confirms the CVE and provides an authoritative advisory record in the Security Update Guide, enabling administrators to map fixes to SKUs once KBs are published. The vendor’s conservative disclosure model reduces the chance of immediate mass weaponization.

Potential risks and why defenders should act fast:

• Local EoP primitives are excellent post‑compromise tools for adversaries. Even if the vulnerability is strictly local (non‑network), attackers commonly achieve initial user‑level code execution via phishing or malicious installers—after which a local EoP allows full takeover. This makes CVE‑2025‑62455 a critical step in realistic attack chains.
• The CVSS vector and aggregator scoring indicate High impact; if accurate, exploitation can yield SYSTEM privileges with confidentiality/integrity impacts. That elevates the severity for servers and admin workstations with MSMQ present.

Uncertainties and caveats:

• As of publication, no public PoC is available and Microsoft’s advisory lacks exploitation specifics. The lack of PoC reduces short‑term automatic exploit risk but does not eliminate targeted threats. Patch urgency remains high for affected hosts.
• Third‑party CVSS scores and vectors may have been extrapolated from limited vendor metadata; expect small changes when Microsoft publishes full KBs and the NVD (or other national CVE authorities) completes enrichment. Administrators should re‑verify the official CVSS vector and affected build list once vendor KBs are released.

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Operational checklist for the next 48–72 hours​

• Inventory: Run a targeted query across your environment to list servers and endpoints with the MSMQ feature installed. Export this list for prioritization.
• Patch planning: Monitor the Microsoft Security Update Guide entry for CVE‑2025‑62455 to obtain KB numbers and test the relevant updates in non‑production tiers as soon as they are available.
• Temporary containment: If patching will be delayed beyond 48 hours, plan to either disable MSMQ on non‑critical systems or restrict network access to the MSMQ service. Document business impact before disabling.
• Increase detection sensitivity: Add rules to the SIEM and EDR for MSMQ crashes, unusual child process launches from system services, and sudden privilege changes on affected hosts.
• Communicate: Notify application owners and change control teams about the vulnerability and potential maintenance windows required for patching and reboots.

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Longer‑term considerations​

• Audit legacy dependencies: Use the advisory as an opportunity to review which business applications rely on MSMQ and whether modern alternatives (Azure Service Bus, RabbitMQ, Kafka) could reduce future surface area and patch complexity. Many organizations retain MSMQ purely for legacy compatibility; reducing that footprint reduces future risk.
• Patch cadence: Ensure your enterprise patching lifecycle can respond to local elevation vulnerabilities with expedited rollout paths for high‑risk components. Treat future MSMQ advisories as high priority because of their potential to enable domain‑wide impact.
• Hardening posture: Enforce least privilege for service accounts and employ just‑in‑time administration where possible so that local user compromises are less likely to provide the preconditions needed for EoP exploits.

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Conclusion​

CVE‑2025‑62455 is a confirmed elevation‑of‑privilege vulnerability in Microsoft Message Queuing (MSMQ) that Microsoft has recorded in its Security Update Guide, and public aggregators report a High severity (CVSS v3.1 = 7.8) tied to improper input validation in MSMQ. The vendor’s public advisory is intentionally brief and lacks exploit details; third‑party trackers provide additional metadata but may update as Microsoft publishes KBs and as NVD/CNAs perform enrichment. Administrators should immediately inventory MSMQ usage, prioritize patch deployment once Microsoft KBs are available, and apply temporary mitigations (disable unused MSMQ, restrict network access, enforce queue permissions) where patches cannot be applied promptly. Given MSMQ’s role in enterprise message infrastructure, the potential operational and security impact of this class of vulnerability is material; treat remediation as a high‑priority operational task. Cautionary note: Public technical details and exploitability status may change rapidly as vendors and researchers publish updates; confirm CVSS vectors, affected builds, and KB mappings against Microsoft’s Update Guide and your patch management tools before finalizing remediation plans.

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Source: MSRC Security Update Guide - Microsoft Security Response Center