{"id":"CVE-2026-33800","state":"PUBLISHED","title":"Junos OS: MX Series: In a VC scenario a high rate of micro-BFD session flaps will cause an FPC crash","description":"An Unchecked Input for Loop Condition vulnerability in the Packet Forwarding Engine (pfe) of Juniper Networks Junos OS on MX Series allows an unauthenticated, adjacent attacker to cause a Denial-of-Service (DoS).Micro-BFD session flaps generate respective up/down events which are queued by PFEMAN for processing. Especially in a Virtual-Chassis (VC) scenario with locality‑bias configured, processing takes a significant amount of time for each event. If these sessions keep flapping, new events are constantly added, and in turn PFEMAN never completes processing these events. This results in the PFEMAN watchdog timer expiring, which causes the FPC to crash and restart, representing a complete service outage.\n\n\nThis issue only affects MX series FPCs up to and including MPC9, and LC2101/2103 and LC480. It does not affect MPC10/11, LC4800/9600, and MX304.\n\nThis issue affects Junos OS on MX Series:\n\n\n  *  all versions before 23.2R2-S7,\n  *  23.4 versions before 23.4R2-S8,\n  *  24.2 versions before 24.2R2-S4,\n  *  24.4 versions before 24.4R2-S3,\n  *  25.2 versions before 25.2R2.","publishedAt":"2026-07-09T21:03:00.614Z","updatedAt":"2026-07-20T13:05:07.325Z","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/RE:M","source":"juniper"},"assigner":"juniper","products":["Juniper Networks Junos OS"],"affected":[{"vendor":"Juniper Networks","product":"Junos OS","defaultStatus":"unaffected","versions":[{"version":"0","status":"affected","lessThan":"23.2R2-S7","versionType":"custom"},{"version":"23.4","status":"affected","lessThan":"23.4R2-S8","versionType":"custom"},{"version":"24.2","status":"affected","lessThan":"24.2R2-S4","versionType":"custom"},{"version":"24.4","status":"affected","lessThan":"24.4R2-S3","versionType":"custom"},{"version":"25.2","status":"affected","lessThan":"25.2R2","versionType":"custom"}],"platforms":["MX Series"]}],"references":["https://supportportal.juniper.net/JSA110075"],"weaknesses":["CWE-606"],"ingestedAt":"2026-10-29T20:11:40.391Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/33xxx/CVE-2026-33800.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-33800","state":"PUBLISHED","datePublished":"2026-07-09T21:03:00.614Z","dateUpdated":"2026-07-20T13:05:07.325Z","assignerShortName":"juniper","assignerOrgId":"8cbe9d5a-a066-4c94-8978-4b15efeae968","dateReserved":"2026-03-23T19:46:13.673Z"},"containers":{"cna":{"title":"Junos OS: MX Series: In a VC scenario a high rate of micro-BFD session flaps will cause an FPC crash","descriptions":[{"lang":"en","value":"An Unchecked Input for Loop Condition vulnerability in the Packet Forwarding Engine (pfe) of Juniper Networks Junos OS on MX Series allows an unauthenticated, adjacent attacker to cause a Denial-of-Service (DoS).Micro-BFD session flaps generate respective up/down events which are queued by PFEMAN for processing. Especially in a Virtual-Chassis (VC) scenario with locality‑bias configured, processing takes a significant amount of time for each event. If these sessions keep flapping, new events are constantly added, and in turn PFEMAN never completes processing these events. This results in the PFEMAN watchdog timer expiring, which causes the FPC to crash and restart, representing a complete service outage.\n\n\nThis issue only affects MX series FPCs up to and including MPC9, and LC2101/2103 and LC480. It does not affect MPC10/11, LC4800/9600, and MX304.\n\nThis issue affects Junos OS on MX Series:\n\n\n  *  all versions before 23.2R2-S7,\n  *  23.4 versions before 23.4R2-S8,\n  *  24.2 versions before 24.2R2-S4,\n  *  24.4 versions before 24.4R2-S3,\n  *  25.2 versions before 25.2R2."}],"affected":[{"vendor":"Juniper Networks","product":"Junos OS","defaultStatus":"unaffected","versions":[{"version":"0","status":"affected","lessThan":"23.2R2-S7","versionType":"custom"},{"version":"23.4","status":"affected","lessThan":"23.4R2-S8","versionType":"custom"},{"version":"24.2","status":"affected","lessThan":"24.2R2-S4","versionType":"custom"},{"version":"24.4","status":"affected","lessThan":"24.4R2-S3","versionType":"custom"},{"version":"25.2","status":"affected","lessThan":"25.2R2","versionType":"custom"}],"platforms":["MX Series"]}],"references":[{"url":"https://supportportal.juniper.net/JSA110075","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":"NOT_DEFINED","subAvailabilityImpact":"LOW","subConfidentialityImpact":"NONE","subIntegrityImpact":"NONE","userInteraction":"NONE","valueDensity":"NOT_DEFINED","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/RE:M","version":"4.0","vulnAvailabilityImpact":"HIGH","vulnConfidentialityImpact":"NONE","vulnIntegrityImpact":"NONE","vulnerabilityResponseEffort":"MODERATE"},"format":"CVSS","scenarios":[{"lang":"en","value":"GENERAL"}]}],"problemTypes":[{"descriptions":[{"cweId":"CWE-606","description":"CWE-606 Unchecked Input for Loop Condition","lang":"en","type":"CWE"}]}],"providerMetadata":{"shortName":"juniper","orgId":"8cbe9d5a-a066-4c94-8978-4b15efeae968","dateUpdated":"2026-07-20T13:05:07.325Z"},"configurations":[{"lang":"en","supportingMedia":[{"base64":false,"type":"text/html","value":"To be exposed to this issue an MX VC needs to be configured with locality bias as follows:<br><br><tt>[ virtual-chassis locality-bias ]</tt>"}],"value":"To be exposed to this issue an MX VC needs to be configured with locality bias as follows:\n\n[ virtual-chassis locality-bias ]"}],"datePublic":"2026-07-08T16:00:00.000Z","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:\n\nJunos OS: 23.2R2-S7, 23.4R2-S8, 24.2R2-S4, 24.4R2-S3, 25.2R2, 25.4R1, and all subsequent releases."}],"value":"The following software releases have been updated to resolve this specific issue:\n\nJunos OS: 23.2R2-S7, 23.4R2-S8, 24.2R2-S4, 24.4R2-S3, 25.2R2, 25.4R1, and all subsequent releases."}],"source":{"advisory":"JSA110075","defect":["1902535"],"discovery":"USER"},"workarounds":[{"lang":"en","supportingMedia":[{"base64":false,"type":"text/html","value":"To reduce the risk of exploitation, configure BFD with an increased holddown-timer, so that the queued events can be processed before a new up event occurs:<br><br><tt>[ ... bfd-liveness-detection&nbsp;holddown-interval milliseconds &lt;value&gt; ]</tt><br><div><br></div>"}],"value":"To reduce the risk of exploitation, configure BFD with an increased holddown-timer, so that the queued events can be processed before a new up event occurs:\n\n[ ... bfd-liveness-detection holddown-interval milliseconds <value> ]"}],"x_generator":{"engine":"Vulnogram 0.1.0-dev"}},"adp":[{"title":"CISA ADP Vulnrichment","metrics":[{"other":{"type":"ssvc","content":{"timestamp":"2026-07-10T13:31:18.681766Z","id":"CVE-2026-33800","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":"2026-07-10T13:31:28.285Z"}}]}}}