CVE-2025-53143 — What Windows administrators need to know about the new MSMQ “type confusion” RCE
Summary (tl;dr)- Microsoft has published a security advisory for CVE-2025-53143: an access-of-resource-using-incompatible-type (a “type confusion”) bug in Microsoft Message Queuing (MSMQ) that can lead to remote code execution when exploited over the network by an authorized actor.
- MSMQ is an optional but widely available Windows component; systems that expose the MSMQ service (TCP/1801) or otherwise accept MSMQ packets are the highest priority for patching, network isolation, or temporary disabling. Independent security researchers and CERTs who have tracked previous MSMQ RCEs recommend patching immediately and/or blocking port 1801 from untrusted networks as a temporary mitigation. (research.checkpoint.com, cert.europa.eu)
- If your environment uses MSMQ in production, treat this as high-priority: verify exposure, inventory MSMQ installs, apply Microsoft’s updates as soon as they are available/validated, and use network controls to reduce exposure while you patch.
MSMQ is a decades-old Windows message-queuing service used by legacy enterprise applications and some modern integrations. Because MSMQ runs as a system service and accepts network messages (default TCP port 1801), remote vulnerabilities in its parsing or dispatch logic can let an attacker execute code in the service’s context — often SYSTEM — with dramatic consequences for confidentiality, integrity, and availability. The security community has previously seen critical RCEs in MSMQ (for example, the 2023 “QueueJumper” family of issues), so new MSMQ RCE advisories should be treated seriously and immediately prioritized by defenders. (research.checkpoint.com, tenable.com)
What Microsoft says (authoritative summary)
Microsoft’s Security Update Guide lists CVE-2025-53143 as a vulnerability in Windows Message Queuing involving “Access of resource using incompatible type (‘type confusion’)” that could allow an authorized attacker to execute code remotely. Administrators should consult Microsoft’s advisory for exact affected builds, severity ratings, and the official remediation guidance (Microsoft’s advisory is the canonical source for patch availability and remedial steps).
Note: when a Microsoft advisory is the primary source, rely on it for the definitive list of affected versions and the correct update packages. If you find conflicting third‑party summaries, prioritize Microsoft’s guidance and published patch KBs.
A short technical explanation — what is a “type confusion” RCE?
- Type confusion (CWE‑843) happens when software treats a memory object as if it were one data type while it is actually another. In languages like C/C++ (which Windows components are commonly written in), that can allow attackers to reinterpret memory in ways that bypass safety checks, corrupt program state, or overwrite function pointers. If that corrupted state is then used to execute a function pointer or return into attacker-controlled data, it can yield arbitrary code execution.
- In a networked service like MSMQ, the attack vector is usually: send specially crafted network packets that trigger a parsing/dispatch path exercising the type-confused behavior; the service ends up dereferencing/calling an incorrect pointer or using corrupted metadata; control flow is hijacked in the context of the service process. Microsoft explicitly identifies CVE-2025-53143 as a type-confusion access bug leading to remote execution, which is consistent with previous MSMQ RCEs. (msrc.microsoft.com, nvd.nist.gov)
- Microsoft’s advisory text describes the vulnerability class and the impact (remote code execution). Exploitability (whether there are public PoCs or in-the-wild exploitation) is determined over time — sometimes Microsoft or third parties will say “Exploited: Yes” or will publish exploitation statuses separately. At the time of writing, Microsoft’s advisory is the authoritative notification; security vendors previously tracked rapid exploitation for other MSMQ RCEs, so treat the vulnerability as high-risk until proven otherwise. (msrc.microsoft.com, research.checkpoint.com)
- Any Windows host with MSMQ installed and reachable by untrusted networks (including the Internet) is high priority. Typical high-risk targets:
- Internet-facing servers with MSMQ or misconfigured firewalls exposing TCP/1801.
- Internal servers that accept MSMQ traffic from a broad set of endpoints (poor segmentation).
- Devices running legacy or vendor applications that bundle MSMQ and may not be patched frequently.
- Machines where MSMQ is installed but not actively used are still a risk if the service is enabled and reachable. Past advisories emphasized inventory and removal/disablement where possible. (cert.europa.eu, research.checkpoint.com)
- Inventory and triage (minutes)
- Identify all machines with MSMQ installed and the service running. On Windows: check “Turn Windows features on or off” (Message Queuing), or query services for “MSMQ”/“Message Queuing.” Audit listening ports for 1801/TCP.
- Apply vendor patches (hours)
- Apply the Microsoft security update(s) that remediate CVE-2025-53143 to affected systems as soon as they are available and validated in your environment. This is the recommended primary fix. Consult the Microsoft Security Update Guide entry for the CVE for exact KBs and patch instructions.
- Temporary network mitigations (if patching will be delayed) (minutes — hours)
- Block inbound access to TCP/1801 at edge firewalls and host firewalls for systems that do not need to receive MSMQ traffic from untrusted sources. If MSMQ traffic should be restricted, lock it down to specific management subnets only. Security vendors and CERTs recommend this exact approach for MSMQ issues while patches are deployed. (research.checkpoint.com, cert.europa.eu)
- Disable the service when not needed (minutes)
- If MSMQ is not required by your environment, disable the Windows feature and stop the mqsvc.exe service. This is a simple and effective hardening step recommended repeatedly for MSMQ vulnerabilities. Some organizations have blocked the port and disabled the feature simultaneously to be safe.
- Detection & monitoring (ongoing)
- Monitor for unusual network connections to TCP/1801, suspicious child processes of mqsvc.exe (e.g., abnormal invocations of cmd.exe, powershell.exe, or unexpected binaries), or new autoruns. Use EDR/SIEM to create alerts on these indicators. CERT-EU and vendor advisories list similar detection pointers for MSMQ exploitation. (cert.europa.eu, tenable.com)
- Test and roll out patches (days)
- Validate updates in a test environment before mass deployment if your change controls require it, but prioritize rapid rollout for exposed or critical assets.
- Network indicators: inbound connections to TCP/1801 from untrusted networks, spikes in MSMQ traffic, or connection patterns that differ from normal business flows.
- Host indicators: unplanned child processes of mqsvc.exe, creation of suspicious scheduled tasks, new services, or persistence backdoors after the service restarts. Examine event logs tied to msmq and system application errors around the time of suspected activity. (cert.europa.eu, tenable.com)
- If you suspect an exploit, isolate the machine from the network (preserve volatile logs), capture memory and disk images for analysis, and consult your incident response playbook. Because MSMQ runs as a privileged service, a successful RCE commonly results in SYSTEM-level access.
- MSMQ has historically been a component that remains enabled in many enterprise footprints for compatibility with older applications. Because it accepts network messages and runs privileged code paths, it has been a fruitful target for security researchers and attackers. The 2023 QueueJumper disclosures (CVE-2023-21554 and related) are a recent example where unauthenticated RCE was found and patched — those incidents stressed the need for inventory, network isolation, and quick patching for message-queuing components. The current CVE continues that pattern: network-facing, privileged service, and high impact if exploited. (research.checkpoint.com, tenable.com)
- Microsoft’s Security Update Guide is the canonical source for CVE-2025-53143 details and patched KBs; always consult it for the authoritative affected products list and update files.
- Independent research and vendor advisories (e.g., Check Point Research’s QueueJumper write-ups and vendor scanners like Tenable/Nessus) provide practical mitigation advice and detection signatures that are valuable for defenders and complement Microsoft’s guidance. Earlier MSMQ advisories from CERTs and vendors repeatedly recommend the same mitigations: patch, disable if unused, block 1801 from untrusted networks, and monitor msqsvc activity. (research.checkpoint.com, tenable.com, cert.europa.eu)
- At the time of drafting this feature, Microsoft’s MSRC entry is the authoritative advisory for CVE-2025-53143. Public third‑party listings (NVD and some aggregators) may take time to index or complete their analysis and scoring. If you rely on vulnerability-management systems, confirm they have the Microsoft advisory linked and the correct patch KBs before marking hosts as remediated. If you use external feeds for automated blocking or patch orchestration, ensure they reference Microsoft’s advisory for the exact KBs rather than a secondary summary.
- Inventory: list systems with MSMQ installed. (PowerShell or group policy can help with large estates.)
- Exposure: identify which MSMQ hosts have port 1801 reachable from untrusted networks; block where appropriate.
- Patch: apply Microsoft’s updates for CVE-2025-53143 as soon as you can validate them in test.
- Disable: if MSMQ is not needed, remove the Windows feature and stop/disable the mqsvc service.
- Monitor: configure EDR/SIEM rules to alert on suspicious mqsvc.exe child processes, unexpected new services, and network traffic to TCP/1801. (cert.europa.eu, tenable.com)
- Incident response: ready your playbook to isolate, collect memory, and preserve logs if you suspect compromise.
Q: Can this be exploited without any credentials?
A: Microsoft labels CVE-2025-53143 as enabling remote code execution from network input and describes the root cause as a type confusion. The advisory wording supplied by Microsoft indicates an “authorized attacker” in your initial snippet; whether authentication is strictly required depends on the precise service path Microsoft describes in the full advisory. Historically, there have been both authenticated and unauthenticated MSMQ RCEs, so treat each advisory with the specifics from Microsoft. Always check the Microsoft advisory for privilege and authentication requirements for this CVE. (msrc.microsoft.com, research.checkpoint.com)
Q: If I block port 1801, am I safe?
A: Blocking 1801 from untrusted networks is a strong short-term mitigation for classic MSMQ network attacks. However, if an attacker already has internal access or an alternate path to send crafted messages (e.g., via compromised application hosts), blocking the external port is not enough; patching and host hardening remain required.
Q: My vendor appliance uses MSMQ — what should I do?
A: Contact the vendor for compatibility guidance and ask whether their product requires a particular MSMQ version or configuration. If immediate updates are not possible, isolate the appliance on a dedicated management network and block unneeded MSMQ traffic until patched.
Closing analysis and recommendations
CVE-2025-53143 is another high-impact reminder that legacy platform components which accept network input and run as high-privilege services are attractive targets — and MSMQ fits that description. Microsoft’s advisory is the source of truth for affected versions and patches; however, independent research and CERT guidance repeatedly recommend the same practical defenders’ playbook: inventory, patch rapidly, block/segment network exposure (TCP/1801), disable unused services, and monitor for suspicious mqsvc behavior. If you run MSMQ in your environment, treat this CVE with urgency: prioritize exposed systems for immediate patching and apply network mitigations while you deploy updates. (msrc.microsoft.com, research.checkpoint.com, cert.europa.eu)
Further reading (authoritative & practical)
- Microsoft Security Update Guide: CVE-2025-53143 (official advisory and patch listing).
- Check Point Research, “QueueJumper” and MSMQ research (previous MSMQ RCE work that illustrates practical exploitation & mitigations).
- CERT-EU / vendor advisories and vulnerability databases for MSMQ mitigation recommendations and detection guidance. (cert.europa.eu, tenable.com)
- I can prepare a step-by-step patch/deployment runbook tailored to your environment (domains, WSUS, SCCM, or Intune), including PowerShell commands to locate and disable MSMQ where not required.
- I can produce sample SIEM/EDR queries and Sysmon rules to detect suspicious mqsvc activity (child processes, unusual network connections, etc.).
Tell me which option you want and a little about your environment (AD/WSUS/SCCM/Intune, scale, whether you have strict change control), and I’ll produce a ready-to-execute playbook.
- Microsoft Security Update Guide — CVE entry for CVE-2025-53143 (Microsoft’s MSRC).
- Check Point Research — QueueJumper and MSMQ threat research (context & mitigation recommendations).
- CERT-EU advisory and vendor guidance on MSMQ mitigations (blocking port 1801, monitoring).
- Vendor scanner signatures and writeups (Tenable/Nessus) and public CVE aggregation pages for MSMQ history & risk context. (tenable.com, nvd.nist.gov)
Source: MSRC Security Update Guide - Microsoft Security Response Center
