CVE-2026-21911
Unknown Unknown - Not Provided
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Publication date: 2026-01-15

Last updated on: 2026-01-15

Assigner: Juniper Networks, Inc.

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.
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Meta Information
Published
2026-01-15
Last Modified
2026-01-15
Generated
2026-06-16
AI Q&A
2026-01-16
EPSS Evaluated
2026-06-15
NVD
CVE-2026-21911
EUVD
EUVD-2026-2699
Affected Vendors & Products
Showing 7 associated CPEs
Vendor Product Version / Range
juniper_networks junos_os_evolved to 21.4R3-S7-EVO (exc)
juniper_networks junos_os_evolved From 22.2 (inc) to 22.2R3-S4-EVO (exc)
juniper_networks junos_os_evolved From 22.3 (inc) to 22.3R3-S3-EVO (exc)
juniper_networks junos_os_evolved From 22.4 (inc) to 22.4R3-S2-EVO (exc)
juniper_networks junos_os_evolved From 23.2 (inc) to 23.2R2-S1-EVO (exc)
juniper_networks junos_os_evolved From 23.4 (inc) to 23.4R1-S2-EVO (exc)
juniper_networks junos_os_evolved 23.4R2-EVO
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Exploitability
CWE
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KEV
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CWE ID Description
CWE-682 The product performs a calculation that generates incorrect or unintended results that are later used in security-critical decisions or resource management.
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Executive Summary

This vulnerability is an Incorrect Calculation issue in the Layer 2 Control Protocol Daemon (l2cpd) of Juniper Networks Junos OS Evolved. It allows an unauthenticated network-adjacent attacker to flap the management interface, which causes the learning of new MAC addresses over label-switched interfaces (LSI) to stop. At the same time, it generates a flood of logs that results in high CPU usage on the affected device.

Impact Analysis

The vulnerability can impact you by causing the device to stop learning new MAC addresses over label-switched interfaces, which may disrupt network operations. Additionally, the flood of logs generated can lead to high CPU usage, potentially degrading device performance or causing denial of service conditions.

Detection Guidance

This vulnerability can be detected by monitoring the system logs for the specific log message generated when the issue occurs. The log message includes details such as '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)'. Checking for this log pattern can help identify the vulnerability being triggered. Specific commands are not provided in the available information.

Mitigation Strategies

Immediate mitigation steps are not detailed in the provided information. However, since the vulnerability affects specific versions of Junos OS Evolved, upgrading to a fixed version (such as 21.4R3-S7-EVO or later versions listed) is implied as a mitigation. No explicit commands or configuration changes are provided.

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