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Vulnerabilities

Vulnerability · CVE-2026-21911

An Incorrect Calculation vulnerability in the Layer 2 Control Protocol Daemon (l2cpd) of Juniper Networks Junos OS Evolved allows an unauthenticated network-adjacent attacker flapp

Published Jan 15, 2026 · catalog updated Jan 15, 2026 · Juniper Networks Junos OS Evolved

Last checked Oct 30, 2026. A connected source was read within the last 7 days.

Check if you run it

No confirmed exploitation is on record for CVE-2026-21911. EPSS is 0.24%. Act only if a listed version of Juniper Networks Junos OS Evolved is installed.

Gaps on this record

  • No vendor fix or required action is stored. Compare the linked advisory before you change production.

Same product and reporting

Severity
High7.1
Known exploitation
Not in CISA/VulnCheck KEV
EPSS
0.24%
Remediation
Version ranges on file
Affected products
vendor Juniper Networks Junos OS Evolved 22.4 <22.4R3-S2-EVO

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_VA

Are you affected?

Enter the version you run. The result uses only the ranges stored on this record.

The check returns affected, not affected, or incomplete. It does not guess a version that is missing from the record.

  • vendor Juniper Networks Junos OS Evolved 22.4 <22.4R3-S2-EVO22.4 <22.4R3-S2-EVO

How to fix CVE-2026-21911

What to do

Three questions, each answered from this record only. Confirm the vendor advisory before you patch.

Should you patch?

No confirmed exploitation is on record for CVE-2026-21911. EPSS is 0.24%. Act only if a listed version of Juniper Networks Junos OS Evolved is installed.

Which versions are affected?

Compare what you have installed with Juniper Networks Junos OS Evolved 22.4 <22.4R3-S2-EVO 22.4 <22.4R3-S2-EVO. Compare the installed version with the linked vendor advisory before you change production.

What should an analyst verify?

No weakness class is stored. EPSS 0.24%. There is no CISA KEV listing. No Exploit-DB or Metasploit reference is linked. Use the source links for the original advisory.

Technology hubs

Juniper Junos OS security

Code

The project this record applies to. Exploit listings stay in References.

No public source repository is identified for this product.

Timeline

Detection, updates, and resolution for this record.

  1. Jan 15, 2026 · EUVD

    Detected

    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

  2. Jan 15, 2026 · EUVD

    Updated

    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

Sources

  • CVE.orgVulnerability recordCVE-2026-21911

    Official CVE identifier

    cve.org
  • FIRST EPSSExploitation probabilityCVE-2026-21911

    30-day exploitation probability 0.24%

    first.org
  • EUVDVulnerability recordEUVD-2026-2699

    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)

    euvd.enisa.europa.eu

References

Freshness

Last verified in this catalog Oct 30, 2026. Significant claims (KEV, EPSS, CVSS, affected ranges) come from the source rows above — open the original publisher for the authoritative advisory.

  • CVE.orgOct 30, 2026
  • FIRST EPSSOct 30, 2026
  • EUVDOct 30, 2026