CVE-2025-59504: Azure Monitor Agent Buffer Overflow Flaw

CVE-2025-59504 Overview

CVE-2025-59504 is a heap-based buffer overflow [CWE-122] in Microsoft Azure Monitor Agent. The flaw allows an unauthorized local attacker to execute arbitrary code on affected systems. Microsoft published the advisory on November 11, 2025, and the National Vulnerability Database (NVD) tracks it with a CVSS v3.1 base score of 7.3. The attack vector is local, requires no privileges, and needs no user interaction. Successful exploitation can corrupt heap memory and divert execution flow within the agent process, impacting host availability and exposing data the agent processes.

Critical Impact
Local attackers can trigger a heap-based buffer overflow in Azure Monitor Agent to execute code on the host and disrupt telemetry collection.

Affected Products

Microsoft Azure Monitor Agent (all versions prior to the patched build referenced in the Microsoft advisory)
Windows hosts running Azure Monitor Agent
Linux hosts running Azure Monitor Agent

Discovery Timeline

2025-11-11 - CVE-2025-59504 published to NVD
2025-11-17 - Last updated in NVD database

Technical Details for CVE-2025-59504

Vulnerability Analysis

The Azure Monitor Agent collects telemetry, performance counters, and log data from virtual machines and on-premises systems for ingestion into Azure Monitor. CVE-2025-59504 is a heap-based buffer overflow within the agent's data-handling logic. An attacker with local access to a host running the agent can craft input that the agent parses into an undersized heap allocation. The write overruns the allocation boundary and corrupts adjacent heap metadata or function pointers. Microsoft classifies the issue under [CWE-122], heap-based buffer overflow. Exploitation does not require authentication to the agent itself, which broadens the population of local users who could trigger the bug.

Root Cause

The root cause is missing or incorrect bounds checking when the agent copies attacker-influenced data into a heap buffer. Length validation does not match the allocated buffer size, so a longer payload writes past the buffer's end. Heap corruption of this type can be steered into control-flow hijack through targeted overwrites of function pointers or object vtables resident in the agent's address space.

Attack Vector

The attack vector is local. An attacker who can place data on the system in a location the agent reads, or who can interact with a local agent interface, can deliver the malformed payload. Because the agent typically runs with elevated privileges to collect system telemetry, successful exploitation can yield code execution at the agent's privilege level. No user interaction is required and the attack complexity is low. Microsoft has not reported in-the-wild exploitation, and the CVE is not listed in the CISA Known Exploited Vulnerabilities catalog. The EPSS exploitation probability remains low at the time of writing.

No verified public proof-of-concept code is available for CVE-2025-59504. Refer to the Microsoft CVE-2025-59504 Advisory for vendor technical details and fixed build information.

Detection Methods for CVE-2025-59504

Indicators of Compromise

Unexpected crashes, restarts, or Watson/crashdump artifacts associated with AzureMonitorAgent or MonAgentCore processes.
Child processes spawned by the Azure Monitor Agent service that deviate from normal telemetry collection binaries.
Anomalous file writes or configuration changes under the agent installation directory on Windows (%ProgramFiles%\Azure Monitor Agent) or Linux (/var/opt/microsoft/azuremonitoragent).

Detection Strategies

Monitor process integrity and memory protection events for the Azure Monitor Agent service, including access violations and stack/heap corruption telemetry.
Alert on the agent process spawning shells, scripting interpreters, or network utilities, which are not part of normal agent behavior.
Inventory installed Azure Monitor Agent versions across the fleet and flag hosts running builds older than the Microsoft-published fix.

Monitoring Recommendations

Forward Azure Monitor Agent service logs and crash telemetry to a central SIEM for correlation.
Track local logon events on hosts running the agent and correlate with agent crashes or service restarts.
Baseline normal agent CPU, memory, and child-process behavior to detect deviations that may indicate exploitation attempts.

How to Mitigate CVE-2025-59504

Immediate Actions Required

Apply the fixed Azure Monitor Agent build referenced in the Microsoft CVE-2025-59504 Advisory to all Windows and Linux hosts.
Validate auto-upgrade is enabled for the Azure Monitor Agent extension on Azure virtual machines and Arc-enabled servers.
Restrict local interactive logon on hosts running the agent to administrators and required service accounts.

Patch Information

Microsoft has published guidance and updated agent packages through the Microsoft Security Response Center. Customers should follow the Microsoft CVE-2025-59504 Advisory for the exact fixed version, update mechanism, and any platform-specific notes. For Azure-managed environments, ensure the Azure Monitor Agent virtual machine extension is configured with automatic minor version upgrades so the patched build is rolled out across the fleet.

Workarounds

Where immediate patching is not possible, reduce the local attack surface by limiting which users can log on to hosts running the agent.
Enforce least privilege on data sources the agent consumes, such as log directories and custom data collection rules, to limit attacker influence over agent input.
Monitor agent process behavior closely until the fixed version is deployed and remove the agent from systems where it is not required.

bash

# Verify installed Azure Monitor Agent version on Linux
/opt/microsoft/azuremonitoragent/bin/mdsd -v

# Verify installed Azure Monitor Agent version on Windows (PowerShell)
Get-ItemProperty "HKLM:\SOFTWARE\Microsoft\Azure Monitor Agent" | Select-Object Version

# Force extension upgrade on an Azure VM
az vm extension set \
  --resource-group <rg> \
  --vm-name <vm> \
  --name AzureMonitorWindowsAgent \
  --publisher Microsoft.Azure.Monitor \
  --enable-auto-upgrade true