Medium [CVE-2026-21911] Incorrect Calculation vulnerability in the Layer 2 Control Protocol Daemon (l2cpd) of Juniper Networks Junos OS Evolved
This medium-severity Juniper Networks advisory covers CVE-2026-21911 affecting Junos, Junos OS, Junos OS Evolved.
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Summary
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 23.2 before 23.2R2-S1-EVO,
- from 23.4 before 23.4R1-S2-EVO, 23.4R2-EVO.
Affected products named by the advisory: EX.
- 22.2
- 22.3
- 22.4
- 23.2
- 23.4
- all versions
Official advisory · high-confidence parse· fetched 2 months ago·verify at source
- 21.4R3-S7-EVO
- 22.2R3-S4-EVO
- 22.3R3-S3-EVO
- 22.4R3-S2-EVO
- 23.2R2-S1-EVO
- 23.4R1-S2-EVO
Official advisory · high-confidence parse· fetched 2 months ago·verify at source
Mitigation
Upgrade to a fixed release: 21.4R3-S7-EVO, 22.2R3-S4-EVO, 22.3R3-S3-EVO, 22.4R3-S2-EVO, 23.2R2-S1-EVO, 23.4R1-S2-EVO. That is the remediation for this advisory.
The vendor advisory may list additional interim mitigations or workarounds not captured here — review it before change work.
Official advisory · high-confidence parse· fetched 2 months ago·verify at source
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