CVE-2024-38257 Overview
CVE-2024-38257 is an information disclosure vulnerability in the Microsoft AllJoyn application programming interface (API) used by Windows for device-to-device communication. The flaw stems from use of uninitialized resources [CWE-908], which can expose memory contents to a remote, unauthenticated attacker. Microsoft assigned the vulnerability a CVSS 3.1 base score of 7.5 and patched it as part of the September 2024 Patch Tuesday release. The Exploit Prediction Scoring System (EPSS) rates the probability of exploitation at 4.334% (89th percentile), reflecting elevated interest relative to most published CVEs.
Critical Impact
A remote, unauthenticated attacker can read sensitive memory contents from affected Windows hosts over the network without user interaction.
Affected Products
- Microsoft Windows 10 (versions 1607, 1809, 21H1, 22H2)
- Microsoft Windows 11 (versions 21H2, 22H2, 23H2)
- Microsoft Windows Server 2016, 2019, 2022, and 2022 23H2
Discovery Timeline
- 2024-09-10 - CVE-2024-38257 published to the National Vulnerability Database (NVD)
- 2024-09-10 - Microsoft released a security update via the Microsoft Security Response Center (MSRC)
- 2024-11-21 - Last updated in the NVD database
Technical Details for CVE-2024-38257
Vulnerability Analysis
The vulnerability resides in the Windows AllJoyn Router Service, which implements the AllJoyn open-source framework for proximity-based, peer-to-peer communication between IoT and application services. The AllJoyn API fails to initialize a resource before use, allowing residual data from prior allocations to be returned to a caller. An attacker who can reach the AllJoyn service across the network can issue crafted requests that solicit responses containing uninitialized memory. The disclosed contents may include data fragments from other processes, message buffers, or kernel-managed structures.
Root Cause
The weakness maps to [CWE-908]: Use of Uninitialized Resource. AllJoyn API code paths allocate memory or structures and return them to a remote caller without first clearing or fully populating the buffer. The previous contents of that memory region remain accessible until overwritten, and a portion of those contents is returned in protocol responses.
Attack Vector
Exploitation requires network access to a host running the AllJoyn Router Service. The service is reachable without authentication and without user interaction. An attacker repeatedly issues crafted AllJoyn requests and parses the responses to harvest fragments of memory. Disclosed bytes can leak cryptographic material, address layout information useful for chaining with code-execution flaws, or other process data.
No verified exploitation code or public proof-of-concept is associated with this CVE. Refer to the Talos Intelligence Vulnerability Report TALOS-2024-1980 for technical details published by the reporting researchers.
Detection Methods for CVE-2024-38257
Indicators of Compromise
- Unexpected inbound connections to the AllJoyn Router Service listening port on Windows endpoints or servers
- Repeated short-lived AllJoyn protocol sessions from a single source address consistent with memory-scraping behavior
- Presence of the AJRouter service running on hosts where AllJoyn is not a documented business requirement
Detection Strategies
- Inventory Windows endpoints with the AJRouter service enabled and flag any externally reachable instances
- Inspect Windows Event Logs and firewall telemetry for unsolicited connections to AllJoyn endpoints from non-trusted network zones
- Apply network signatures that match malformed or anomalous AllJoyn protocol exchanges originating from outside the management plane
Monitoring Recommendations
- Track patch state across all listed Windows 10, Windows 11, and Windows Server builds against the September 2024 update baseline
- Alert on creation, restart, or reconfiguration of the AllJoyn Router Service on production servers
- Correlate AllJoyn service activity with broader east-west traffic baselines to identify reconnaissance patterns
How to Mitigate CVE-2024-38257
Immediate Actions Required
- Apply the September 2024 Microsoft security updates referenced in the Microsoft Security Update Guide to every affected build listed above
- Confirm patch deployment status on Windows Server 2016, 2019, 2022, and 2022 23H2, which are commonly exposed in datacenter environments
- Restrict inbound network access to the AllJoyn Router Service from untrusted networks until patches are confirmed applied
Patch Information
Microsoft addressed CVE-2024-38257 in the September 10, 2024 cumulative updates for all supported Windows 10, Windows 11, and Windows Server versions. The fix ensures that AllJoyn API resources are properly initialized before being returned to callers. Refer to the Microsoft Security Update Guide for the specific Knowledge Base article matching each Windows build.
Workarounds
- Disable the AllJoyn Router Service (AJRouter) on hosts that do not require AllJoyn-based device discovery or communication
- Block inbound traffic to AllJoyn service ports at host-based and perimeter firewalls on systems where the service must remain enabled
- Segment IoT and proximity-communication workloads onto isolated VLANs to limit the reachable attack surface
# Disable the AllJoyn Router Service on Windows where it is not required
sc.exe config AJRouter start= disabled
sc.exe stop AJRouter
# Verify current service state
sc.exe query AJRouter
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
