CVE-2025-30656 in Junos OS
Summary
by MITRE • 04/09/2025
An Improper Handling of Additional Special Element vulnerability in the Packet Forwarding Engine (PFE) of Juniper Networks Junos OS on MX Series with MS-MPC, MS-MIC and SPC3, and SRX Series, allows an unauthenticated, network-based attacker to cause a Denial-of-Service (DoS).
If the SIP ALG processes specifically formatted SIP invites, a memory corruption will occur which will lead to a crash of the FPC processing these packets. Although the system will automatically recover with the restart of the FPC, subsequent SIP invites will cause the crash again and lead to a sustained DoS.
This issue affects Junos OS on MX Series and SRX Series:
* all versions before 21.2R3-S9, * 21.4 versions before 21.4R3-S10, * 22.2 versions before 22.2R3-S6, * 22.4 versions before 22.4R3-S5, * 23.2 versions before 23.2R2-S3, * 23.4 versions before 23.4R2-S3, * 24.2 versions before 24.2R1-S2, 24.2R2.
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Analysis
by VulDB Data Team • 01/24/2026
The vulnerability identified as CVE-2025-30656 represents a critical improper handling of additional special elements flaw within the Packet Forwarding Engine of Juniper Networks Junos OS operating on MX Series devices equipped with MS-MPC, MS-MIC, and SPC3 components, alongside SRX Series platforms. This weakness specifically manifests when the Session Initiation Protocol Application Layer Gateway (SIP ALG) processes specially crafted SIP INVITE messages that contain malformed or unexpected elements. The flaw resides in how the system handles these additional special elements during packet processing, creating an exploitable condition that can be leveraged by unauthenticated attackers positioned within the network.
The technical implementation of this vulnerability stems from insufficient validation and sanitization of SIP protocol elements within the FPC (Flexible Packet Processor) context. When a maliciously formatted SIP INVITE packet reaches the system, the SIP ALG component attempts to parse and process these additional special elements without adequate bounds checking or memory management controls. This processing error results in memory corruption that ultimately triggers a system crash of the affected FPC module. The vulnerability is particularly concerning because it operates at the packet processing level where the system's core forwarding engine operates, making it difficult to detect and mitigate through conventional network monitoring approaches.
The operational impact of this vulnerability extends beyond simple service disruption to create sustained denial-of-service conditions that can severely impact communication infrastructure. While the system does exhibit automatic recovery mechanisms through FPC restart procedures, this remediation is temporary and does not prevent subsequent exploitation attempts. The attacker can repeatedly send malformed SIP INVITE packets to cause multiple FPC crashes, leading to prolonged service degradation that affects voice and video communication services relying on SIP protocols. This persistent nature of the vulnerability makes it particularly dangerous for mission-critical infrastructure where continuous availability is paramount, and the recovery process may introduce additional service interruptions.
Security practitioners should note that this vulnerability aligns with CWE-129 Improper Validation of Array Index and CWE-787 Out-of-bounds Write categories, both of which are classified under the Common Weakness Enumeration framework as critical memory safety issues. From an adversarial perspective, this vulnerability maps to ATT&CK technique T1499.004 Network Denial of Service within the Network Service Exhaustion sub-technique, enabling attackers to systematically exhaust system resources through targeted packet injection. The attack vector requires only network-based access and does not require authentication, making it particularly attractive to threat actors seeking to disrupt services without detection. Organizations should prioritize immediate patching of affected systems to address this vulnerability, as the exploitation window remains open across multiple Junos OS version lines.
The affected software versions span across multiple release branches including 21.2R3-S9, 21.4R3-S10, 22.2R3-S6, 22.4R3-S5, 23.2R2-S3, 23.4R2-S3, 24.2R1-S2, and 24.2R2, indicating that this vulnerability has been present across multiple major releases and requires comprehensive remediation across all supported platforms. The vulnerability's persistence across different hardware platforms and software versions suggests a fundamental flaw in the SIP ALG implementation that affects the entire Juniper Junos OS ecosystem, making coordinated patch management essential for complete protection. Organizations should also implement network segmentation and monitoring to detect anomalous SIP traffic patterns that could indicate exploitation attempts.