Juniper Junos OS <21.2R3-S9 Control Plane Firewall Filter Bypass
CVE-2025-52951 Published on July 11, 2025
Junos OS: IPv6 firewall filter fails to match payload-protocol
A Protection Mechanism Failure vulnerability in kernel filter processing of Juniper Networks Junos OS allows an attacker sending IPv6 traffic destined to the device to effectively bypass any firewall filtering configured on the interface.
Due to an issue with Junos OS kernel filter processing, the 'payload-protocol' match is not being supported, causing any term containing it to accept all packets without taking any other action. In essence, these firewall filter terms were being processed as an 'accept' for all traffic on the interface destined for the control plane, even when used in combination with other match criteria.
This issue only affects firewall filters protecting the device's control plane. Transit firewall filtering is unaffected by this vulnerability.
This issue affects Junos OS:
* all versions before 21.2R3-S9,
* from 21.4 before 21.4R3-S11,
* from 22.2 before 22.2R3-S7,
* from 22.4 before 22.4R3-S7,
* from 23.2 before 23.2R2-S4,
* from 23.4 before 23.4R2-S5,
* from 24.2 before 24.2R2-S1,
* from 24.4 before 24.4R1-S2, 24.4R2.
This is a more complete fix for previously published CVE-2024-21607 (JSA75748).
Vulnerability Analysis
CVE-2025-52951 can be exploited with network access, and does not require authorization privileges or user interaction. This vulnerability is considered to have a low attack complexity. The potential impact of an exploit of this vulnerability is considered to have no impact on confidentiality, with no impact on integrity, and no impact on availability.
Timeline
Initial Publication
Clarified that only traffic destined to the control plane is affected 6 days later.
Weakness Type
Protection Mechanism Failure
The product does not use or incorrectly uses a protection mechanism that provides sufficient defense against directed attacks against the product. This weakness covers three distinct situations. A "missing" protection mechanism occurs when the application does not define any mechanism against a certain class of attack. An "insufficient" protection mechanism might provide some defenses - for example, against the most common attacks - but it does not protect against everything that is intended. Finally, an "ignored" mechanism occurs when a mechanism is available and in active use within the product, but the developer has not applied it in some code path.
Products Associated with CVE-2025-52951
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Affected Versions
Juniper Networks Junos OS:- Before 21.2R3-S9 is affected.
- Version 21.4 and below 21.4R3-S11 is affected.
- Version 22.2 and below 22.2R3-S7 is affected.
- Version 22.4 and below 22.4R3-S7 is affected.
- Version 23.2 and below 23.2R2-S4 is affected.
- Version 23.4 and below 23.4R2-S5 is affected.
- Version 24.2 and below 24.2R2-S1 is affected.
- Version 24.4 and below 24.4R1-S2, 24.4R2 is affected.
Exploit Probability
EPSS (Exploit Prediction Scoring System) scores estimate the probability that a vulnerability will be exploited in the wild within the next 30 days. The percentile shows you how this score compares to all other vulnerabilities.