Juniper Junos OS Evolved up to 23.3 Layer 2 Control Protocol Daemon calculation

Summaryinfo

A vulnerability classified as critical has been found in Juniper Junos OS Evolved up to 22.1/22.2/22.3/23.1/23.3. Impacted is an unknown function of the component Layer 2 Control Protocol Daemon. Performing a manipulation results in calculation. This vulnerability is known as CVE-2026-21911. Access to the local network is required for this attack. No exploit is available. It is recommended to upgrade the affected component.

Detailsinfo

A vulnerability, which was classified as critical, was found in Juniper Junos OS Evolved up to 22.1/22.2/22.3/23.1/23.3. This affects some unknown processing of the component Layer 2 Control Protocol Daemon. The manipulation with an unknown input leads to a calculation vulnerability. CWE is classifying the issue as CWE-682. The product performs a calculation that generates incorrect or unintended results that are later used in security-critical decisions or resource management. This is going to have an impact on availability. The summary by CVE is:

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.

The advisory is shared at supportportal.juniper.net. This vulnerability is uniquely identified as CVE-2026-21911 since 01/05/2026. The exploitability is told to be easy. Access to the local network is required for this attack to succeed. No form of authentication is needed for exploitation. Neither technical details nor an exploit are publicly available.

Upgrading to version 21.4R3-S7-EVO, 22.2R3-S4-EVO, 22.3R3-S3-EVO, 22.4R3-S2-EVO, 23.2R2-S1-EVO, 23.4R1-S2-EVO or 23.4R2-EVO eliminates this vulnerability.

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Productinfo

Type

• Router Operating System

Vendor

• Juniper

Name

• Junos OS Evolved

Version

• 22.0
• 22.1
• 22.2
• 22.3
• 23.0
• 23.1
• 23.2
• 23.3

License

• commercial

Website

• Vendor: https://www.juniper.net/

CPE 2.3info

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