# CVE-2026-21911

## Summary

- **CVE ID:** CVE-2026-21911
- **Severity:** HIGH
- **CVSS Score:** 7.1 (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:Amber)
- **CWE:** CWE-682
- **Published:** Jan 15, 2026
- **Last Modified:** Mar 12, 2026

## Description

An Incorrect Calculation vulnerability in the Layer 2 Control

Protocol 

 Daemon (l2cpd) of Juniper Networks Junos OS Evolved allows an unauthenticated network-adjacent attacker flapping the management interface to cause the learning of new MACs over label-switched interfaces (LSI) to stop while generating a flood of logs, resulting in high CPU usage.

When the issue is seen, the following log message will be generated:

op:1 flag:0x6 mac:xx:xx:xx:xx:xx:xx bd:2 ifl:13302 reason:0(REASON_NONE) i-op:6(INTRNL_OP_HW_FORCE_DELETE) status:10 lstatus:10 err:26(GETIFBD_VALIDATE_FAILED) err-reason 4(IFBD_VALIDATE_FAIL_EPOCH_MISMATCH) hw_wr:0x4 ctxsync:0 fwdsync:0  rtt-id:51 p_ifl:0  fwd_nh:0 svlbnh:0 event:- smask:0x100000000 dmask:0x0 mplsmask 0x1 act:0x5800 extf:0x0 pfe-id 0 hw-notif-ifl 13302 programmed-ifl 4294967295 pseudo-vtep underlay-ifl-idx 0 stack:GET_MAC, ALLOCATE_MAC, GET_IFL, GET_IFF, GET_IFBD, STOP, 


This issue affects Junos OS Evolved: 

  *  all versions before 21.4R3-S7-EVO, 
  *  from 22.2 before 22.2R3-S4-EVO, 
  *  from 22.3 before 22.3R3-S3-EVO, 
  *  from 22.4 before 22.4R3-S2-EVO, 
  *  from 23.2 before 23.2R2-S1-EVO, 
  *  from 23.4 before 23.4R1-S2-EVO, 23.4R2-EVO.

## Affected Products

- Juniper Networks — Junos OS Evolved (0)
- Juniper Networks — Junos OS Evolved (22.2)
- Juniper Networks — Junos OS Evolved (22.3)
- Juniper Networks — Junos OS Evolved (22.4)
- Juniper Networks — Junos OS Evolved (23.2)
- Juniper Networks — Junos OS Evolved (23.4)

## References

- [CNA](https://supportportal.juniper.net/JSA106010)
- [CNA](https://kb.juniper.net/JSA106010)

## Exploitation Prediction (EPSS)

- **EPSS Score:** 0.22%
- **EPSS Percentile:** 13.0

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_Exported from OnDuty AI Vulnerability Intelligence on 2026-09-10._