CVE-2021-42130

What it actually does

CVE-2021-42130 is a deserialization of untrusted data vulnerability in Ivanti Avalanche versions before 6.3.3. An attacker with network access to the Inforail Service and low-privileged access can submit crafted serialized data that is processed by the service, causing attacker-controlled object deserialization and enabling arbitrary code execution in the security context of the Avalanche service. Successful exploitation can result in full confidentiality, integrity, and availability compromise of the Avalanche server and potentially managed mobile-device or warehouse-device infrastructure.

Why it matters to the business

Compromise of Ivanti Avalanche can disrupt device management operations, allow attackers to alter device configurations, steal operational or enrollment data, deploy malicious changes to managed devices, or use the server as a foothold into adjacent enterprise systems. The high CVSS score and elevated EPSS indicate meaningful exploitation likelihood even though it is not currently listed in CISA KEV, so internet-exposed or broadly reachable Avalanche deployments should be treated as high priority.

How an attack unfolds

An attacker first identifies an Ivanti Avalanche deployment exposing the Inforail Service. After obtaining or using low-privileged access required to interact with the service, the attacker sends a crafted serialized payload designed to trigger unsafe deserialization. The vulnerable service reconstructs attacker-controlled objects without sufficient validation, allowing execution of code or commands under the service account. From there, the attacker may install persistence, dump credentials, tamper with Avalanche-managed device policies, move laterally, or stage additional tooling from the compromised server.

How to fix it

Upgrade Ivanti Avalanche to version 6.3.3 or later. If immediate upgrade is not possible, restrict network access to the Inforail Service to only trusted management hosts, block exposure from untrusted networks and the internet, enforce strong authentication, and monitor the service closely for abnormal serialized payloads, crashes, or child process execution. Run Avalanche services with least-privileged service accounts where operationally feasible and rotate credentials that may have been exposed if compromise is suspected.

How to confirm the fix worked

Confirm the installed Ivanti Avalanche version is 6.3.3 or later using the product console, installed-program inventory, package metadata, or vendor-supported version command. Verify that the Inforail Service is not reachable from untrusted networks by performing network scans from representative internal and external vantage points. Validate firewall rules and access-control lists limiting service access. Review vulnerability scanner results to ensure CVE-2021-42130 is no longer reported. Where possible, perform a safe authenticated configuration review rather than exploit testing in production.

Typical attack path

1. Scan for Ivanti Avalanche systems with reachable Inforail Service endpoints.
2. Authenticate or otherwise obtain the low-privileged access needed to communicate with the service.
3. Send a malicious serialized object payload to the vulnerable Inforail Service.
4. Achieve code execution in the context of the Avalanche service process.
5. Run reconnaissance commands, write files, or download second-stage tooling.
6. Escalate privileges if needed and establish persistence.
7. Access Avalanche configuration, credentials, device-management data, or pivot to adjacent systems.

How to detect it

Investigate whether the Inforail Service received unusual or malformed serialized data, especially around authentication events or service errors. Review Ivanti Avalanche application logs, Inforail Service logs, Windows Event Logs, endpoint detection telemetry, process creation logs, service crash dumps, and network flow records. Look for Java deserialization exceptions, object stream corruption errors, unexpected service restarts, abnormal outbound connections from the Avalanche server, or child processes spawned by the Avalanche/Inforail service such as command shells, scripting engines, download utilities, or archive tools. Network defenders should search packet captures or IDS telemetry for Java serialization magic bytes sent to the Inforail Service. If exploitation is suspected, preserve memory, service logs, recent file-system changes, scheduled tasks, service modifications, and service-account authentication history.

• Inforail Service
• AC ED 00 05
• java.io.ObjectInputStream
• java.io.StreamCorruptedException
• java.io.InvalidClassException
• java.io.InvalidStreamException
• java.io.NotSerializableException
• java.lang.ClassNotFoundException
• cmd.exe /c
• powershell.exe
• wscript.exe
• cscript.exe
• certutil.exe
• bitsadmin.exe
• rundll32.exe
• regsvr32.exe

What your security team should do

• Patch Ivanti Avalanche to 6.3.3 or later as the top priority.
• Immediately restrict Inforail Service access to trusted administrative or application components only.
• Inventory all Avalanche servers, including legacy Wavelink/Ivanti installations, and identify any systems below 6.3.3.
• Search historical logs for suspicious deserialization errors, service crashes, unexpected child processes, and outbound connections from the Avalanche server.
• Review Avalanche service-account privileges and reduce them where possible.
• Rotate credentials stored on or used by Avalanche if there is evidence of exploitation.
• Add network detection for Java serialized object streams or anomalous traffic directed at the Inforail Service.
• Increase monitoring for Avalanche servers because EPSS indicates elevated exploitation probability despite no KEV listing.