{"id":"CVE-2026-21905","state":"PUBLISHED","title":"Junos OS: SRX Series, MX Series with MX-SPC3 or MS-MPC: Receipt of multiple specific SIP messages results in flow management process crash","description":"A Loop with Unreachable Exit Condition ('Infinite Loop') vulnerability in the SIP application layer gateway (ALG) of Juniper Networks Junos OS on SRX Series and MX Series with MX-SPC3 or MS-MPC allows an unauthenticated network-based attacker sending specific SIP messages over TCP to crash the flow management process, leading to a Denial of Service (DoS).\n\nOn SRX Series, and MX Series with MX-SPC3 or MS-MPC service cards, receipt of multiple SIP messages causes the SIP headers to be parsed incorrectly, eventually causing a continuous loop and leading to a watchdog timer expiration, crashing the flowd process on SRX Series and MX Series with MX-SPC3, or mspmand process on MX Series with MS-MPC.\n\nThis issue only occurs over TCP. SIP messages sent over UDP cannot trigger this issue.\n\nThis issue affects Junos OS on SRX Series and MX Series with MX-SPC3 and MS-MPC:\n\n\n\n  *  all versions before 21.2R3-S10, \n  *  from 21.4 before 21.4R3-S12, \n  *  from 22.4 before 22.4R3-S8, \n  *  from 23.2 before 23.2R2-S5, \n  *  from 23.4 before 23.4R2-S6, \n  *  from 24.2 before 24.2R2-S3, \n  *  from 24.4 before 24.4R2-S1, \n  *  from 25.2 before 25.2R1-S1, 25.2R2.","publishedAt":"2026-01-15T20:19:22.158Z","updatedAt":"2026-01-16T16:26:02.071Z","severity":{"score":8.7,"label":"High","version":"4.0","vector":"CVSS:4.0/AV:N/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"],"affected":[{"vendor":"Juniper Networks","product":"Junos OS","defaultStatus":"unaffected","versions":[{"version":"0","status":"affected","lessThan":"21.2R3-S10","versionType":"semver"},{"version":"21.4","status":"affected","lessThan":"21.4R3-S12","versionType":"semver"},{"version":"22.4","status":"affected","lessThan":"22.4R3-S8","versionType":"semver"},{"version":"23.2","status":"affected","lessThan":"23.2R2-S5","versionType":"semver"},{"version":"23.4","status":"affected","lessThan":"23.4R2-S6","versionType":"semver"},{"version":"24.2","status":"affected","lessThan":"24.2R2-S3","versionType":"semver"},{"version":"24.4","status":"affected","lessThan":"24.4R2-S1","versionType":"semver"},{"version":"25.2","status":"affected","lessThan":"25.2R1-S1, 25.2R2","versionType":"semver"}],"platforms":["SRX Series","MX Series with MX-SPC3","MX Series with MS-MPC"]}],"references":["https://supportportal.juniper.net/JSA106004","https://kb.juniper.net/JSA106004"],"weaknesses":["CWE-835"],"ingestedAt":"2026-10-29T20:11:10.572Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/21xxx/CVE-2026-21905.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-21905","state":"PUBLISHED","datePublished":"2026-01-15T20:19:22.158Z","dateUpdated":"2026-01-16T16:26:02.071Z","assignerShortName":"juniper","assignerOrgId":"8cbe9d5a-a066-4c94-8978-4b15efeae968","dateReserved":"2026-01-05T17:32:48.710Z"},"containers":{"cna":{"title":"Junos OS: SRX Series, MX Series with MX-SPC3 or MS-MPC: Receipt of multiple specific SIP messages results in flow management process crash","descriptions":[{"lang":"en","value":"A Loop with Unreachable Exit Condition ('Infinite Loop') vulnerability in the SIP application layer gateway (ALG) of Juniper Networks Junos OS on SRX Series and MX Series with MX-SPC3 or MS-MPC allows an unauthenticated network-based attacker sending specific SIP messages over TCP to crash the flow management process, leading to a Denial of Service (DoS).\n\nOn SRX Series, and MX Series with MX-SPC3 or MS-MPC service cards, receipt of multiple SIP messages causes the SIP headers to be parsed incorrectly, eventually causing a continuous loop and leading to a watchdog timer expiration, crashing the flowd process on SRX Series and MX Series with MX-SPC3, or mspmand process on MX Series with MS-MPC.\n\nThis issue only occurs over TCP. SIP messages sent over UDP cannot trigger this issue.\n\nThis issue affects Junos OS on SRX Series and MX Series with MX-SPC3 and MS-MPC:\n\n\n\n  *  all versions before 21.2R3-S10, \n  *  from 21.4 before 21.4R3-S12, \n  *  from 22.4 before 22.4R3-S8, \n  *  from 23.2 before 23.2R2-S5, \n  *  from 23.4 before 23.4R2-S6, \n  *  from 24.2 before 24.2R2-S3, \n  *  from 24.4 before 24.4R2-S1, \n  *  from 25.2 before 25.2R1-S1, 25.2R2."}],"affected":[{"vendor":"Juniper Networks","product":"Junos OS","defaultStatus":"unaffected","versions":[{"version":"0","status":"affected","lessThan":"21.2R3-S10","versionType":"semver"},{"version":"21.4","status":"affected","lessThan":"21.4R3-S12","versionType":"semver"},{"version":"22.4","status":"affected","lessThan":"22.4R3-S8","versionType":"semver"},{"version":"23.2","status":"affected","lessThan":"23.2R2-S5","versionType":"semver"},{"version":"23.4","status":"affected","lessThan":"23.4R2-S6","versionType":"semver"},{"version":"24.2","status":"affected","lessThan":"24.2R2-S3","versionType":"semver"},{"version":"24.4","status":"affected","lessThan":"24.4R2-S1","versionType":"semver"},{"version":"25.2","status":"affected","lessThan":"25.2R1-S1, 25.2R2","versionType":"semver"}],"platforms":["SRX Series","MX Series with MX-SPC3","MX Series with MS-MPC"]}],"references":[{"url":"https://supportportal.juniper.net/JSA106004","tags":["vendor-advisory"]},{"url":"https://kb.juniper.net/JSA106004","tags":["vendor-advisory"]}],"metrics":[{"cvssV3_1":{"attackComplexity":"LOW","attackVector":"NETWORK","availabilityImpact":"HIGH","baseScore":7.5,"baseSeverity":"HIGH","confidentialityImpact":"NONE","integrityImpact":"NONE","privilegesRequired":"NONE","scope":"UNCHANGED","userInteraction":"NONE","vectorString":"CVSS:3.1/AV:N/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":"NETWORK","baseScore":8.7,"baseSeverity":"HIGH","privilegesRequired":"NONE","providerUrgency":"AMBER","subAvailabilityImpact":"LOW","subConfidentialityImpact":"NONE","subIntegrityImpact":"NONE","userInteraction":"NONE","valueDensity":"CONCENTRATED","vectorString":"CVSS:4.0/AV:N/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-835","description":"CWE-835 Loop with Unreachable Exit Condition ('Infinite Loop')","lang":"en","type":"CWE"}]}],"providerMetadata":{"shortName":"juniper","orgId":"8cbe9d5a-a066-4c94-8978-4b15efeae968","dateUpdated":"2026-01-15T20:19:22.158Z"},"configurations":[{"lang":"en","supportingMedia":[{"base64":false,"type":"text/html","value":"The SIP ALG must be enabled to be vulnerable to this issue. The SIP ALG is enabled by default on MX-SPC3 and some SRX Series platforms. For other platforms, the following configuration is required:<br><br>\n\n<tt><span style=\"background-color: rgb(255, 255, 255);\">[security alg sip enable]</span></tt><br>\n<br>On SRX Series and MX Series with MX-SPC3, the SIP ALG status can be confirmed via the 'show security alg status' command:<br>\n<br>\n<tt>user@junos&gt; show security alg status</tt><br>\n<tt>ALG Status:</tt><br>\n...<br>\n<tt>&nbsp; SIP  &nbsp; &nbsp; : Enabled</tt><br>"}],"value":"The SIP ALG must be enabled to be vulnerable to this issue. The SIP ALG is enabled by default on MX-SPC3 and some SRX Series platforms. For other platforms, the following configuration is required:\n\n\n\n[security alg sip enable]\n\n\nOn SRX Series and MX Series with MX-SPC3, the SIP ALG status can be confirmed via the 'show security alg status' command:\n\n\n\nuser@junos> show security alg status\n\nALG Status:\n\n...\n\n  SIP      : Enabled"}],"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: 21.2R3-S10, 21.4R3-S12, 22.4R3-S8, 23.2R2-S5, 23.4R2-S6, 24.2R2-S3, 24.4R2-S1, 25.2R1-S1, 25.2R2, 25.4R1, and all subsequent releases."}],"value":"The following software releases have been updated to resolve this specific issue: 21.2R3-S10, 21.4R3-S12, 22.4R3-S8, 23.2R2-S5, 23.4R2-S6, 24.2R2-S3, 24.4R2-S1, 25.2R1-S1, 25.2R2, 25.4R1, and all subsequent releases."}],"source":{"advisory":"JSA106004","defect":["1876029"],"discovery":"USER"},"workarounds":[{"lang":"en","supportingMedia":[{"base64":false,"type":"text/html","value":"Where practical, use a firewall filter to limit SIP traffic over TCP.<br><br>Alternately, if the SIP ALG is not required, it can be explicitly disabled on SRX Series and MX Series with MX-SPC3 via:<br><br><tt># set security alg sip disable</tt><br><br>"}],"value":"Where practical, use a firewall filter to limit SIP traffic over TCP.\n\nAlternately, if the SIP ALG is not required, it can be explicitly disabled on SRX Series and MX Series with MX-SPC3 via:\n\n# set security alg sip disable"}],"x_generator":{"engine":"Vulnogram 0.1.0-dev"}},"adp":[{"title":"CISA ADP Vulnrichment","metrics":[{"other":{"type":"ssvc","content":{"timestamp":"2026-01-16T16:25:54.871316Z","id":"CVE-2026-21905","options":[{"Exploitation":"none"},{"Automatable":"yes"},{"Technical Impact":"partial"}],"role":"CISA Coordinator","version":"2.0.3"}}}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2026-01-16T16:26:02.071Z"}}]}}}