{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-21905","assignerOrgId":"8cbe9d5a-a066-4c94-8978-4b15efeae968","state":"PUBLISHED","assignerShortName":"juniper","dateReserved":"2026-01-05T17:32:48.710Z","datePublished":"2026-01-15T20:19:22.158Z","dateUpdated":"2026-01-16T16:26:02.071Z"},"containers":{"cna":{"affected":[{"defaultStatus":"unaffected","platforms":["SRX Series","MX Series with MX-SPC3","MX Series with MS-MPC"],"product":"Junos OS","vendor":"Juniper Networks","versions":[{"lessThan":"21.2R3-S10","status":"affected","version":"0","versionType":"semver"},{"lessThan":"21.4R3-S12","status":"affected","version":"21.4","versionType":"semver"},{"lessThan":"22.4R3-S8","status":"affected","version":"22.4","versionType":"semver"},{"lessThan":"23.2R2-S5","status":"affected","version":"23.2","versionType":"semver"},{"lessThan":"23.4R2-S6","status":"affected","version":"23.4","versionType":"semver"},{"lessThan":"24.2R2-S3","status":"affected","version":"24.2","versionType":"semver"},{"lessThan":"24.4R2-S1","status":"affected","version":"24.4","versionType":"semver"},{"lessThan":"25.2R1-S1, 25.2R2","status":"affected","version":"25.2","versionType":"semver"}]}],"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:

\n\n[security alg sip enable]
\n
On SRX Series and MX Series with MX-SPC3, the SIP ALG status can be confirmed via the 'show security alg status' command:
\n
\nuser@junos> show security alg status
\nALG Status:
\n...
\n  SIP     : Enabled
"}],"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","descriptions":[{"lang":"en","supportingMedia":[{"base64":false,"type":"text/html","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).

On 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.

This issue only occurs over TCP. SIP messages sent over UDP cannot trigger this issue.

This issue affects Junos OS on SRX Series and MX Series with MX-SPC3 and MS-MPC:

"}],"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."}],"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."}],"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":{"orgId":"8cbe9d5a-a066-4c94-8978-4b15efeae968","shortName":"juniper","dateUpdated":"2026-01-15T20:19:22.158Z"},"references":[{"tags":["vendor-advisory"],"url":"https://supportportal.juniper.net/JSA106004"},{"tags":["vendor-advisory"],"url":"https://kb.juniper.net/JSA106004"}],"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"},"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","workarounds":[{"lang":"en","supportingMedia":[{"base64":false,"type":"text/html","value":"Where practical, use a firewall filter to limit SIP traffic over TCP.

Alternately, if the SIP ALG is not required, it can be explicitly disabled on SRX Series and MX Series with MX-SPC3 via:

# set security alg sip disable

"}],"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":[{"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"}}}],"title":"CISA ADP Vulnrichment","providerMetadata":{"orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","shortName":"CISA-ADP","dateUpdated":"2026-01-16T16:26:02.071Z"}}]}}