{"id":"CVE-2026-21911","state":"PUBLISHED","title":"Junos OS Evolved: Flapping management interface causes MAC learning on label-switched interfaces to stop","description":"An Incorrect Calculation vulnerability in the Layer 2 Control\n\nProtocol \n\n 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.\n\nWhen the issue is seen, the following log message will be generated:\n\nop: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, \n\n\nThis issue affects Junos OS Evolved: \n\n  *  all versions before 21.4R3-S7-EVO, \n  *  from 22.2 before 22.2R3-S4-EVO, \n  *  from 22.3 before 22.3R3-S3-EVO, \n  *  from 22.4 before 22.4R3-S2-EVO, \n  *  from 23.2 before 23.2R2-S1-EVO, \n  *  from 23.4 before 23.4R1-S2-EVO, 23.4R2-EVO.","publishedAt":"2026-01-15T20:23:54.924Z","updatedAt":"2026-01-15T20:51:32.531Z","severity":{"score":7.1,"label":"High","version":"4.0","vector":"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","source":"juniper"},"assigner":"juniper","products":["Juniper Networks Junos OS Evolved"],"affected":[{"vendor":"Juniper Networks","product":"Junos OS Evolved","defaultStatus":"unaffected","versions":[{"version":"0","status":"affected","lessThan":"21.4R3-S7-EVO","versionType":"semver"},{"version":"22.2","status":"affected","lessThan":"22.2R3-S4-EVO","versionType":"semver"},{"version":"22.3","status":"affected","lessThan":"22.3R3-S3-EVO","versionType":"semver"},{"version":"22.4","status":"affected","lessThan":"22.4R3-S2-EVO","versionType":"semver"},{"version":"23.2","status":"affected","lessThan":"23.2R2-S1-EVO","versionType":"semver"},{"version":"23.4","status":"affected","lessThan":"23.4R1-S2-EVO, 23.4R2-EVO","versionType":"semver"}]}],"references":["https://supportportal.juniper.net/JSA106010","https://kb.juniper.net/JSA106010"],"weaknesses":["CWE-682"],"ingestedAt":"2026-10-29T20:11:10.572Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/21xxx/CVE-2026-21911.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-21911","state":"PUBLISHED","datePublished":"2026-01-15T20:23:54.924Z","dateUpdated":"2026-01-15T20:51:32.531Z","assignerShortName":"juniper","assignerOrgId":"8cbe9d5a-a066-4c94-8978-4b15efeae968","dateReserved":"2026-01-05T17:32:48.710Z"},"containers":{"cna":{"title":"Junos OS Evolved: Flapping management interface causes MAC learning on label-switched interfaces to stop","descriptions":[{"lang":"en","value":"An Incorrect Calculation vulnerability in the Layer 2 Control\n\nProtocol \n\n 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.\n\nWhen the issue is seen, the following log message will be generated:\n\nop: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, \n\n\nThis issue affects Junos OS Evolved: \n\n  *  all versions before 21.4R3-S7-EVO, \n  *  from 22.2 before 22.2R3-S4-EVO, \n  *  from 22.3 before 22.3R3-S3-EVO, \n  *  from 22.4 before 22.4R3-S2-EVO, \n  *  from 23.2 before 23.2R2-S1-EVO, \n  *  from 23.4 before 23.4R1-S2-EVO, 23.4R2-EVO."}],"affected":[{"vendor":"Juniper Networks","product":"Junos OS Evolved","defaultStatus":"unaffected","versions":[{"version":"0","status":"affected","lessThan":"21.4R3-S7-EVO","versionType":"semver"},{"version":"22.2","status":"affected","lessThan":"22.2R3-S4-EVO","versionType":"semver"},{"version":"22.3","status":"affected","lessThan":"22.3R3-S3-EVO","versionType":"semver"},{"version":"22.4","status":"affected","lessThan":"22.4R3-S2-EVO","versionType":"semver"},{"version":"23.2","status":"affected","lessThan":"23.2R2-S1-EVO","versionType":"semver"},{"version":"23.4","status":"affected","lessThan":"23.4R1-S2-EVO, 23.4R2-EVO","versionType":"semver"}]}],"references":[{"url":"https://supportportal.juniper.net/JSA106010","tags":["vendor-advisory"]},{"url":"https://kb.juniper.net/JSA106010","tags":["vendor-advisory"]}],"metrics":[{"cvssV3_1":{"attackComplexity":"LOW","attackVector":"ADJACENT_NETWORK","availabilityImpact":"HIGH","baseScore":6.5,"baseSeverity":"MEDIUM","confidentialityImpact":"NONE","integrityImpact":"NONE","privilegesRequired":"NONE","scope":"UNCHANGED","userInteraction":"NONE","vectorString":"CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","version":"3.1"},"format":"CVSS","scenarios":[{"lang":"en","value":"GENERAL"}]},{"cvssV4_0":{"Automatable":"YES","Recovery":"AUTOMATIC","Safety":"NOT_DEFINED","attackComplexity":"LOW","attackRequirements":"NONE","attackVector":"ADJACENT","baseScore":7.1,"baseSeverity":"HIGH","privilegesRequired":"NONE","providerUrgency":"AMBER","subAvailabilityImpact":"LOW","subConfidentialityImpact":"NONE","subIntegrityImpact":"NONE","userInteraction":"NONE","valueDensity":"CONCENTRATED","vectorString":"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","version":"4.0","vulnAvailabilityImpact":"HIGH","vulnConfidentialityImpact":"NONE","vulnIntegrityImpact":"NONE","vulnerabilityResponseEffort":"MODERATE"},"format":"CVSS","scenarios":[{"lang":"en","value":"GENERAL"}]}],"problemTypes":[{"descriptions":[{"cweId":"CWE-682","description":"CWE-682 Incorrect Calculation","lang":"en","type":"CWE"}]}],"providerMetadata":{"shortName":"juniper","orgId":"8cbe9d5a-a066-4c94-8978-4b15efeae968","dateUpdated":"2026-01-15T20:23:54.924Z"},"configurations":[{"lang":"en","supportingMedia":[{"base64":false,"type":"text/html","value":"This issue affects label-switched interfaces configured for VPLS. For example:<br><br><tt>[routing-instances &lt;name&gt; instance-type vpls]<br>[routing-instances &lt;name&gt; protocols vpls]</tt>"}],"value":"This issue affects label-switched interfaces configured for VPLS. For example:\n\n[routing-instances <name> instance-type vpls]\n[routing-instances <name> protocols vpls]"}],"datePublic":"2026-01-14T17:00:00.000Z","exploits":[{"lang":"en","supportingMedia":[{"base64":false,"type":"text/html","value":"Juniper SIRT is not aware of any malicious exploitation of this vulnerability."}],"value":"Juniper SIRT is not aware of any malicious exploitation of this vulnerability."}],"solutions":[{"lang":"en","supportingMedia":[{"base64":false,"type":"text/html","value":"The following software releases have been updated to resolve this specific issue: 21.4R3-S7-EVO, 22.2R3-S4-EVO, 22.3R3-S3-EVO, 22.4R3-S2-EVO, 23.2R2-S1-EVO, 23.4R1-S2-EVO, 23.4R2-EVO, 24.2R1-EVO, and all subsequent releases."}],"value":"The following software releases have been updated to resolve this specific issue: 21.4R3-S7-EVO, 22.2R3-S4-EVO, 22.3R3-S3-EVO, 22.4R3-S2-EVO, 23.2R2-S1-EVO, 23.4R1-S2-EVO, 23.4R2-EVO, 24.2R1-EVO, and all subsequent releases."}],"source":{"advisory":"JSA106010","defect":["1802153"],"discovery":"USER"},"workarounds":[{"lang":"en","supportingMedia":[{"base64":false,"type":"text/html","value":"There are no known workarounds for this issue.<br>"}],"value":"There are no known workarounds for this issue."}],"x_generator":{"engine":"Vulnogram 0.1.0-dev"}},"adp":[{"title":"CISA ADP Vulnrichment","metrics":[{"other":{"type":"ssvc","content":{"timestamp":"2026-01-15T20:51:26.965443Z","id":"CVE-2026-21911","options":[{"Exploitation":"none"},{"Automatable":"no"},{"Technical Impact":"partial"}],"role":"CISA Coordinator","version":"2.0.3"}}}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2026-01-15T20:51:32.531Z"}}]}}}