CVE-2026-21909

Junos OS and Junos OS Evolved: Receipt of specific IS-IS update packet causes memory leak leading to RPD crash

Published Jan 15, 2026 CVSS 4.0 · 7.1 High EPSS < 1% KEV · Not listed
Description
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.

Analysis

AI-generated

Technical impact

A missing release of memory after effective lifetime vulnerability in the routing protocol daemon (rpd) allows an unauthenticated attacker controlling a neighboring IS‑IS node to send a specially crafted update packet, causing a memory leak. Continued receipt of such packets exhausts all available memory, causing the rpd process to crash and resulting in a denial‑of‑service condition for the router.

Affected Systems

Juniper Networks Junos OS and Junos OS Evolved devices are affected. For Junos OS the issue impacts all releases from 23.2 up to but not including 23.2R2, from 23.4 up to but not including the first release after 23.4R1‑S2, and from 24.1 up to but not including 24.1R2. For Junos OS Evolved the affected range mirrors the Junos OS range, with the same release boundaries. Devices running versions earlier than 23.2R1 or 23.2R1‑EVO are not affected.

Risk and Exploitability

The severity is rated at CVSS 7.1 (medium) and the EPSS score is below 1%, indicating a low probability of exploitation in the wild. Nonetheless, the vulnerability is unauthenticated and requires only that an attacker control a neighboring IS‑IS node, which is relatively trivial to achieve in many environments. Because the exploit simply involves sending repeated update packets that trigger a memory leak, operators should treat this as a moderate risk until the software is patched. The vulnerability is not listed in the CISA KEV catalog as of the current data.

Remediation

Vendor Solution

The following software releases have been updated to resolve this specific issue: Junos OS: 23.2R2, 23.4R1-S2, 23.4R2, 24.1R2, 24.2R1, and all subsequent releases. Junos OS Evolved: 23.2R2-EVO, 23.4R1-S2-EVO, 23.4R2-EVO, 24.1R2-EVO, 24.2R1-EVO, and all subsequent releases.


Vendor Workaround

There are no known workarounds for this issue.


OpenCVE Recommended Actions

  • Upgrade Junos OS to release 23.2R2 or later on all vulnerable devices.
  • Upgrade Junos OS Evolved to release 23.2R2‑EVO or later on all vulnerable devices.
  • Limit IS‑IS adjacencies to trusted peers or remove untrusted adjacencies from routers running affected software.
  • Use the 'show task memory detail' command to monitor the rpd process memory usage and take corrective action if memory growth indicates a leak.

Generated by OpenCVE AI on April 18, 2026 at 05:58 UTC.

Tracking

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Advisories

No advisories available
History
Type Values Removed Values Added
First Time appeared Juniper
Juniper junos
Juniper junos Os Evolved
CPEs cpe:2.3:o:juniper:junos:23.2:-:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:23.2:r1-s1:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:23.2:r1-s2:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:23.2:r1:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:23.4:-:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:23.4:r1-s1:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:23.4:r1:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:23.4:r2:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:24.1:-:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:24.1:r1:*:*:*:*:*:*
cpe:2.3:o:juniper:junos_os_evolved:23.2:-:*:*:*:*:*:*
cpe:2.3:o:juniper:junos_os_evolved:23.2:r1-s1:*:*:*:*:*:*
cpe:2.3:o:juniper:junos_os_evolved:23.2:r1-s2:*:*:*:*:*:*
cpe:2.3:o:juniper:junos_os_evolved:23.2:r1:*:*:*:*:*:*
cpe:2.3:o:juniper:junos_os_evolved:23.4:-:*:*:*:*:*:*
cpe:2.3:o:juniper:junos_os_evolved:23.4:r1-s1:*:*:*:*:*:*
cpe:2.3:o:juniper:junos_os_evolved:23.4:r1:*:*:*:*:*:*
cpe:2.3:o:juniper:junos_os_evolved:23.4:r2:*:*:*:*:*:*
cpe:2.3:o:juniper:junos_os_evolved:24.1:-:*:*:*:*:*:*
cpe:2.3:o:juniper:junos_os_evolved:24.1:r1:*:*:*:*:*:*
Vendors & Products Juniper
Juniper junos
Juniper junos Os Evolved
Type Values Removed Values Added
First Time appeared Juniper Networks
Juniper Networks junos Os
Juniper Networks junos Os Evolved
Vendors & Products Juniper Networks
Juniper Networks junos Os
Juniper Networks junos Os Evolved
Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

Type Values Removed Values Added
Description 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.
Title Junos OS and Junos OS Evolved: Receipt of specific IS-IS update packet causes memory leak leading to RPD crash
Weaknesses CWE-401
References
Metrics cvssV3_1

{'score': 6.5, 'vector': 'CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H'}

cvssV4_0

{'score': 7.1, '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/AU:Y/R:A/V:C/RE:M/U:Green'}

Weaknesses
  • CWE-401

    Missing Release of Memory after Effective Lifetime

Sources

Status
PUBLISHED
Assigner
juniper
Published
Updated
Jan 15, 2026, 8:52 PM
Reserved
Jan 5, 2026, 5:32 PM
Status
Analyzed
Published
Jan 15, 2026, 9:16 PM
Modified
Jun 17, 2026, 10:19 AM