Junos OS: Use After Free
CVE-2025-52946 is a high-severity use after free vulnerability in Junos OS from Juniper Networks, with a CVSS 3.1 base score of 7.5 out of 10. It can be exploited remotely over the network by an unauthenticated attacker, without any action from a user. The record lists versions 21.2R3-S9, 22.2R3-S6, 22.4R3-S5 as the first without the flaw, so updating Junos OS to one of those releases or later removes the exposure. There is no confirmed exploitation so far. EPSS estimates a 0.52% chance of exploitation within 30 days, which is low compared with other CVEs.
High severity with no evidence of exploitation so far.
What to do
- Update Junos OS to 21.2R3-S9 or 22.2R3-S6 or 22.4R3-S5 or 23.2R2-S3, whichever matches your release line, or a later version.
- Update Junos OS Evolved to 22.4R3-S5-EVO or 23.2R2-S3-EVO or 23.4R2-S4-EVO or 24.2R2-EVO, whichever matches your release line, or a later version.
- Update Junos to 21.2 or a later version.
- Read the advisory on supportportal.juniper.net for workarounds and exact fixed builds.
- Until you can update, restrict network access to the affected service so it is not reachable from untrusted networks.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Juniper Networks | Junos OS | before 21.2R3-S9; 21.4 and later; 22.2 up to, but not including, 22.2R3-S6; 22.4 up to, but not including, 22.4R3-S5; 23.2 up to, but not including, 23.2R2-S3; 23.4 up to, but not including, 23.4R2-S4; 24.2 up to, but not including, 24.2R2 | 21.2R3-S9, 22.2R3-S6, 22.4R3-S5, 23.2R2-S3, 23.4R2-S4, 24.2R2 |
| Juniper Networks | Junos OS Evolved | before 22.4R3-S5-EVO; 23.2-EVO up to, but not including, 23.2R2-S3-EVO; 23.4-EVO up to, but not including, 23.4R2-S4-EVO; 24.2-EVO up to, but not including, 24.2R2-EVO | 22.4R3-S5-EVO, 23.2R2-S3-EVO, 23.4R2-S4-EVO, 24.2R2-EVO |
| Juniper Networks | Junos | before 21.2; 21.2; 21.4; 22.2; 22.4; 23.2; 23.4; 24.2 | 21.2 |
Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.
How the severity score breaks down
- Attack vector
- NetworkCan be exploited remotely over a network, including the internet.
- Attack complexity
- LowNo special conditions are needed; the attack works reliably.
- Privileges required
- NoneNo account or login is needed.
- User interaction
- NoneNo action by a victim is required.
- Scope
- UnchangedImpact stays within the vulnerable component.
- Confidentiality
- NoneNo data is disclosed.
- Integrity
- NoneNothing can be modified.
- Availability
- HighThe component can be taken down completely.
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H. Scored by CNA (juniper.net).
| Scoring system | Score | Severity | Scored by |
|---|---|---|---|
| CVSS 4.0 | 8.7 | High | CNA (juniper.net) |
| CVSS 3.1 | 7.5 | High | CNA (juniper.net) |
Official description
A Use After Free vulnerability in the routing protocol daemon (rpd) of Juniper Networks Junos OS and Juniper Networks Junos OS Evolved allows an attacker sending a BGP update with a specifically malformed AS PATH to cause rpd to crash, resulting in a Denial of Service (DoS). Continuous receipt of the malformed AS PATH attribute will cause a sustained DoS condition. On all Junos OS and Junos OS Evolved platforms, the rpd process will crash and restart when a specifically malformed AS PATH is received within a BGP update and traceoptions are enabled. This issue only affects systems with BGP traceoptions enabled and requires a BGP session to be already established. Systems without BGP traceoptions enabled are not impacted by this issue. This issue affects: Junos OS: * All versions before 21.2R3-S9, * all versions of 21.4, * from 22.2 before 22.2R3-S6, * from 22.4 before 22.4R3-S5, * from 23.2 before 23.2R2-S3, * from 23.4 before 23.4R2-S4, * from 24.2 before 24.2R2; Junos OS Evolved: * All versions before 22.4R3-S5-EVO, * from 23.2-EVO before 23.2R2-S3-EVO, * from 23.4-EVO before 23.4R2-S4-EVO, * from 24.2-EVO before 24.2R2-EVO. This is a more complete fix for previously published CVE-2024-39549 (JSA83011).
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Use After Free
The product reuses or references memory after it has been freed. At some point afterward, the memory may be allocated again and saved in another pointer, while the original pointer references a location somewhere within the new allocation. Any operations using the original pointer are no longer valid because the memory belongs to the code that operates on the new pointer.
How developers prevent this class of flaw
- Choose a language that provides automatic memory management.
- When freeing pointers, be sure to set them to NULL once they are freed. However, the utilization of multiple or complex data structures may lower the usefulness of this strategy.
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: none, automatable: yes, technical impact: partial).
- Record last changed materially (score, affected products, status or references).
References
Advisories
Other vulnerabilities in Junos OS
- 7.5 High severity
- 9.8 Critical severity
- 9.8 Critical severity
- 8.8 High severity
- 8.8 High severity
- 7.5 High severity
Recent Use After Free vulnerabilities
- 7.8 High severity
- 7.8 High severity
- 7.8 High severity
- 7.8 High severity
- 7.8 High severity
- 7.8 High severity
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