Juniper Junos OS SRX Series ICMPv6 Denial-of-Service Vulnerability (CVE-2026-33790)

hello@craftedsignal.io — Wed, 19 Jun 2024 12:00:00 +0000

CVE-2026-33790 is a vulnerability affecting Juniper Networks Junos OS on SRX Series devices. The vulnerability resides in the flow daemon (flowd) and is triggered by sending a specific, malformed ICMPv6 packet to the device during NAT64 translation. This causes the srxpfe process to crash and restart. The continuous receipt and processing of these malformed packets will repeatedly crash the srxpfe process, resulting in a sustained Denial of Service (DoS) condition. The vulnerability is specific to ICMPv6 traffic and does not affect IPv4 or other IPv6 traffic types. Affected versions include versions before 21.2R3-S10, all versions of 21.3, versions 21.4 before 21.4R3-S12, all versions of 22.1, versions 22.2 before 22.2R3-S8, all versions of 22.4, versions 22.4 before 22.4R3-S9, versions 23.2 before 23.2R2-S6, versions 23.4 before 23.4R2-S7, versions 24.2 before 24.2R2-S3, versions 24.4 before 24.4R2-S3, and versions 25.2 before 25.2R1-S2, 25.2R2.

Attack Chain

Attacker identifies a vulnerable Juniper SRX Series device running Junos OS with NAT64 enabled.
The attacker crafts a specific, malformed ICMPv6 packet.
The attacker sends the malformed ICMPv6 packet to the SRX device.
The SRX device receives the ICMPv6 packet and attempts NAT64 translation.
Due to the malformed packet, the flowd process encounters an improper check condition.
The srxpfe process crashes as a result of the malformed ICMPv6 packet.
The srxpfe process restarts automatically.
The attacker continuously sends malformed ICMPv6 packets to repeatedly crash the srxpfe process, sustaining a Denial-of-Service condition.

Impact

Successful exploitation of this vulnerability leads to a Denial-of-Service condition on the affected Juniper SRX Series device. This can disrupt network services, impacting connectivity and availability for legitimate users. The repeated crashing of the srxpfe process can severely degrade device performance and potentially lead to complete service outage. The number of potential victims is dependent on the number of deployed, vulnerable Juniper SRX series devices with NAT64 enabled.

Recommendation

Apply the appropriate patch or upgrade to a fixed version of Junos OS on SRX Series devices as specified in the Juniper advisory to remediate CVE-2026-33790.
Monitor network traffic for unusual or malformed ICMPv6 packets destined for SRX devices performing NAT64, as this may indicate exploitation attempts, and deploy the provided Sigma rule to detect such activity.
Implement rate limiting for ICMPv6 traffic at the network perimeter to mitigate the impact of potential DoS attacks targeting this vulnerability, preventing the continuous crashing of the srxpfe process.

Juniper Networks J-Web Remote Code Execution Vulnerability Exploitation

hello@craftedsignal.io — Wed, 03 Jan 2024 15:00:00 +0000

Juniper Networks devices, specifically those using the J-Web interface, are susceptible to remote code execution vulnerabilities. These vulnerabilities, including CVE-2023-36844, CVE-2023-36845, CVE-2023-36846, and CVE-2023-36847, allow attackers to execute arbitrary code on affected systems. The primary attack vector involves sending malicious requests to the /webauth_operation.php endpoint with manipulated PHPRC parameters. Successful exploitation grants the attacker unauthorized access, potentially leading to data theft, network compromise, and complete system control. Exploitation attempts have been observed targeting vulnerable Juniper SRX and EX series devices. Publicly available exploit code exists, increasing the likelihood of widespread exploitation.

Attack Chain

The attacker identifies a vulnerable Juniper Networks device running J-Web.
The attacker crafts a malicious HTTP POST request targeting the /webauth_operation.php endpoint.
The request includes a PHPRC parameter containing PHP code designed to execute commands on the server.
The vulnerable J-Web interface processes the request without proper sanitization.
The attacker's PHP code executes with the privileges of the web server process.
The attacker establishes a reverse shell connection to an external server using nc or bash -i.
The attacker uses the reverse shell to execute commands, enumerate the system, and escalate privileges.
The attacker installs a persistent backdoor, exfiltrates sensitive data, and pivots to other internal systems.

Impact

Successful exploitation of these vulnerabilities allows attackers to gain complete control over Juniper Networks devices. This can lead to data theft, network outages, and further compromise of internal networks. The vulnerabilities affect a wide range of Juniper SRX and EX series devices, potentially impacting numerous organizations. If successful, attackers can deploy ransomware, steal intellectual property, or disrupt critical network services.

Recommendation

Deploy the Sigma rules provided in this brief to your SIEM to detect exploitation attempts (rules: "Juniper J-Web RCE via webauth_operation.php" and "Juniper J-Web RCE Reverse Shell").
Inspect web server logs for requests to /webauth_operation.php?PHPRC=* (IOC: url: /webauth_operation.php?PHPRC=*) and investigate any matches.
Monitor for outbound network connections from Juniper devices to unusual or suspicious IP addresses, which may indicate a reverse shell (rule: "Juniper J-Web RCE Reverse Shell").
Patch CVE-2023-36844, CVE-2023-36845, CVE-2023-36846, and CVE-2023-36847 on all affected Juniper devices immediately.

SRX Series - CraftedSignal Threat Feed

Juniper Junos OS SRX Series ICMPv6 Denial-of-Service Vulnerability (CVE-2026-33790)

Attack Chain

Impact

Recommendation

Juniper Networks J-Web Remote Code Execution Vulnerability Exploitation

Attack Chain

Impact

Recommendation