CVE-2026-21909
What it is
A Missing Release of Memory after Effective Lifetime vulnerability in the routing protocol daemon (rpd) Juniper Networks Junos OS and Junos OS Evolved allows an unauthenticated attacker controlling an adjacent IS-IS neighbor to send a specific update packet causing a memory leak. Continued receipt and processing of these packets will exhaust all available memory, crashing rpd and creating a Denial of Service (DoS) condition. Memory usage can be monitored through the use of the 'show task memory detail' command. For example: user@junos> show task memory detail | match ted-infra TED-INFRA-COOKIE 25 1072 28 1184 229 user@junos> show task memory detail | match ted-infra TED-INFRA-COOKIE 31 1360 34 1472 307 This issue affects: Junos OS: * from 23.2 before 23.2R2, * from 23.4 before 23.4R1-S2, 23.4R2, * from 24.1 before 24.1R2; Junos OS Evolved: * from 23.2 before 23.2R2-EVO, * from 23.4 before 23.4R1-S2-EVO, 23.4R2-EVO, * from 24.1 before 24.1R2-EVO. This issue does not affect Junos OS versions before 23.2R1 or Junos OS Evolved versions before 23.2R1-EVO.
At a glance
- Exploitability
- Can be exploited from the same network segment without logging in. High risk of service disruption.
- Exploit odds
- 0.2% chance of exploitation in the next 30 days (EPSS).
- Fix
- A patch, advisory or fixed version is referenced. Upgrade or apply it.
Timeline
- PublishedDisclosed publicly on CVE.org and NVD
- Last updatedMost recent change to the record
Why it ranks here
- Exploited in the wild: no, CISA does not list it.
- Exploit odds: 0.2% in the next 30 days (EPSS).
- Severity: 7.1 HIGH (CVSS).
- Fix: a patch or advisory is linked.
Details
- Published
- Last modified
- Exploit probability
- 0.2% · EPSS, next 30 days
- Weakness
- CWE-401
- Record status
- Analyzed
Affected
- Juniper Junos 23.2
- Juniper Junos 23.4
- Juniper Junos 24.1
- Juniper Junos Os Evolved 23.2
- Juniper Junos Os Evolved 23.4
- Juniper Junos Os Evolved 24.1
Attack profile CVSS 4.0 · 7.1
- Attack vector
- Adjacent network
- Complexity
- Low
- Attack requirements
- None
- Privileges needed
- None
- User interaction
- None
- Confidentiality
- None
- Integrity
- None
- Availability
- High
Raw vector
CVSS:4.0/AV:A/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:L/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:Y/R:A/V:C/RE:M/U:Green
Is it in your code?
Hand this to your coding agent. It searches your project for the affected products and checks versions. Nothing leaves your machine.
Read https://cve-list.com/agent/cve/CVE-2026-21909.md and follow it. Check whether this project is affected by CVE-2026-21909. Read only. Don't change anything and don't upload my code. Tell me yes, no or not sure, with the file as proof.
