Junos OS: Improper Initialization
CVE-2026-101957 is a high-severity improper initialization 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 23.2R2-S7.7, 23.4R2-S8.13, 24.2R2-S5.5 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 0.55% 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 23.2R2-S7.7 or 23.4R2-S8.13 or 24.2R2-S5.5 or 24.4R2-S5, whichever matches your release line, or a later version.
- Update Junos OS Evolved to 23.2R2-S7.7-EVO or 23.4R2-S8.11-EVO or 24.2R2-S5.6-EVO or 24.4R2-S5-EVO, whichever matches your release line, or a later version.
- 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 23.2R2-S7.7; 23.4 up to, but not including, 23.4R2-S8.13; 24.2 up to, but not including, 24.2R2-S5.5; 24.4 up to, but not including, 24.4R2-S5; 25.2 up to, but not including, 25.2R2-S2; 25.4 up to, but not including, 25.4R1-S3; 26.2 up to, but not including, 26.2R1-S2 | 23.2R2-S7.7, 23.4R2-S8.13, 24.2R2-S5.5, 24.4R2-S5, 25.2R2-S2, 25.4R1-S3 |
| Juniper Networks | Junos OS Evolved | before 23.2R2-S7.7-EVO; 23.4 up to, but not including, 23.4R2-S8.11-EVO; 24.2 up to, but not including, 24.2R2-S5.6-EVO; 24.4 up to, but not including, 24.4R2-S5-EVO; 25.2 up to, but not including, 25.2R2-S2-EVO; 25.4 up to, but not including, 25.4R1-S3-EVO; 26.2 up to, but not including, 26.2R1-S2-EVO; 23.4X100; and 2 more ranges | 23.2R2-S7.7-EVO, 23.4R2-S8.11-EVO, 24.2R2-S5.6-EVO, 24.4R2-S5-EVO, 25.2R2-S2-EVO, 25.4R1-S3-EVO |
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
An Improper Initialization vulnerability in the routing protocol daemon (rpd) of Juniper Networks Junos OS and Junos OS Evolved allows a remote BGP peer to cause an rpd crash via an LLGR-stale route update readvertised to a configured non-LLGR peer group.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Improper Initialization
The product does not initialize or incorrectly initializes a resource.
How developers prevent this class of flaw
- Use a language that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid. For example, in Java, if the programmer does not explicitly initialize a variable, then the code could produce a compile-time error (if the variable is local) or automatically initialize the variable to the default value for the variable's type. In Perl, if explicit initialization is not performed, then a default value of undef is assigned, which is interpreted as 0, false, or an equivalent value depending on the context in which the variable is accessed.
- Identify all variables and data stores that receive information from external sources, and apply input validation to make sure that they are only initialized to expected values.
- Explicitly initialize all your variables and other data stores, either during declaration or just before the first usage.
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
Other references
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 Improper Initialization vulnerabilities
- 7.0 High severity
- 8.3 High severity
- 7.8 High severity
- 7.3 High severity
- 9.8 Critical severity
- 8.1 High severity
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