CVE-2026-21905 (GCVE-0-2026-21905)

Vulnerability from cvelistv5 – Published: 2026-01-15 20:19 – Updated: 2026-01-16 16:26
VLAI?
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
Summary
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: * all versions before 21.2R3-S10,  * from 21.4 before 21.4R3-S12,  * from 22.4 before 22.4R3-S8,  * from 23.2 before 23.2R2-S5,  * from 23.4 before 23.4R2-S6,  * from 24.2 before 24.2R2-S3,  * from 24.4 before 24.4R2-S1,  * from 25.2 before 25.2R1-S1, 25.2R2.
Severity ?
7.5 (High)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
8.7 (High)
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
CWE
  • CWE-835 - Loop with Unreachable Exit Condition ('Infinite Loop')
Assigner
References
Impacted products
Vendor Product Version
Juniper Networks Junos OS Affected: 0 , < 21.2R3-S10 (semver)
Affected: 21.4 , < 21.4R3-S12 (semver)
Affected: 22.4 , < 22.4R3-S8 (semver)
Affected: 23.2 , < 23.2R2-S5 (semver)
Affected: 23.4 , < 23.4R2-S6 (semver)
Affected: 24.2 , < 24.2R2-S3 (semver)
Affected: 24.4 , < 24.4R2-S1 (semver)
Affected: 25.2 , < 25.2R1-S1, 25.2R2 (semver)
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              "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:\u003cbr\u003e\u003cbr\u003e\n\n\u003ctt\u003e\u003cspan style=\"background-color: rgb(255, 255, 255);\"\u003e[security alg sip enable]\u003c/span\u003e\u003c/tt\u003e\u003cbr\u003e\n\u003cbr\u003eOn SRX Series and MX Series with MX-SPC3, the SIP ALG status can be confirmed via the \u0027show security alg status\u0027 command:\u003cbr\u003e\n\u003cbr\u003e\n\u003ctt\u003euser@junos\u0026gt; show security alg status\u003c/tt\u003e\u003cbr\u003e\n\u003ctt\u003eALG Status:\u003c/tt\u003e\u003cbr\u003e\n...\u003cbr\u003e\n\u003ctt\u003e\u0026nbsp; SIP  \u0026nbsp; \u0026nbsp; : Enabled\u003c/tt\u003e\u003cbr\u003e"
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      "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",
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    "cveId": "CVE-2026-21905",
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    "dateUpdated": "2026-01-16T16:26:02.071Z",
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\"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H\", \"integrityImpact\": \"NONE\", \"userInteraction\": \"NONE\", \"attackComplexity\": \"LOW\", \"availabilityImpact\": \"HIGH\", \"privilegesRequired\": \"NONE\", \"confidentialityImpact\": \"NONE\"}, \"scenarios\": [{\"lang\": \"en\", \"value\": \"GENERAL\"}]}, {\"format\": \"CVSS\", \"cvssV4_0\": {\"Safety\": \"NOT_DEFINED\", \"version\": \"4.0\", \"Recovery\": \"AUTOMATIC\", \"baseScore\": 8.7, \"Automatable\": \"YES\", \"attackVector\": \"NETWORK\", \"baseSeverity\": \"HIGH\", \"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\", \"providerUrgency\": \"AMBER\", \"userInteraction\": \"NONE\", \"attackComplexity\": \"LOW\", \"attackRequirements\": \"NONE\", \"privilegesRequired\": \"NONE\", \"subIntegrityImpact\": \"NONE\", \"vulnIntegrityImpact\": \"NONE\", \"subAvailabilityImpact\": \"LOW\", \"vulnAvailabilityImpact\": \"HIGH\", \"subConfidentialityImpact\": \"NONE\", \"vulnConfidentialityImpact\": \"NONE\", \"vulnerabilityResponseEffort\": \"MODERATE\"}, \"scenarios\": [{\"lang\": \"en\", \"value\": \"GENERAL\"}]}], \"affected\": [{\"vendor\": \"Juniper Networks\", \"product\": \"Junos OS\", \"versions\": [{\"status\": \"affected\", \"version\": \"0\", \"lessThan\": \"21.2R3-S10\", \"versionType\": \"semver\"}, {\"status\": \"affected\", \"version\": \"21.4\", \"lessThan\": \"21.4R3-S12\", \"versionType\": \"semver\"}, {\"status\": \"affected\", \"version\": \"22.4\", \"lessThan\": \"22.4R3-S8\", \"versionType\": \"semver\"}, {\"status\": \"affected\", \"version\": \"23.2\", \"lessThan\": \"23.2R2-S5\", \"versionType\": \"semver\"}, {\"status\": \"affected\", \"version\": \"23.4\", \"lessThan\": \"23.4R2-S6\", \"versionType\": \"semver\"}, {\"status\": \"affected\", \"version\": \"24.2\", \"lessThan\": \"24.2R2-S3\", \"versionType\": \"semver\"}, {\"status\": \"affected\", \"version\": \"24.4\", \"lessThan\": \"24.4R2-S1\", \"versionType\": \"semver\"}, {\"status\": \"affected\", \"version\": \"25.2\", \"lessThan\": \"25.2R1-S1, 25.2R2\", \"versionType\": \"semver\"}], \"platforms\": [\"SRX Series\", \"MX Series with MX-SPC3\", \"MX Series with MS-MPC\"], \"defaultStatus\": \"unaffected\"}], \"exploits\": [{\"lang\": \"en\", \"value\": \"Juniper SIRT is not aware of any malicious exploitation of this vulnerability.\", \"supportingMedia\": [{\"type\": \"text/html\", \"value\": \"Juniper SIRT is not aware of any malicious exploitation of this vulnerability.\", \"base64\": false}]}], \"solutions\": [{\"lang\": \"en\", \"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.\", \"supportingMedia\": [{\"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.\", \"base64\": false}]}], \"datePublic\": \"2026-01-14T17:00:00.000Z\", \"references\": [{\"url\": \"https://supportportal.juniper.net/JSA106004\", \"tags\": [\"vendor-advisory\"]}, {\"url\": \"https://kb.juniper.net/JSA106004\", \"tags\": [\"vendor-advisory\"]}], \"workarounds\": [{\"lang\": \"en\", \"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\", \"supportingMedia\": [{\"type\": \"text/html\", \"value\": \"Where practical, use a firewall filter to limit SIP traffic over TCP.\u003cbr\u003e\u003cbr\u003eAlternately, if the SIP ALG is not required, it can be explicitly disabled on SRX Series and MX Series with MX-SPC3 via:\u003cbr\u003e\u003cbr\u003e\u003ctt\u003e# set security alg sip disable\u003c/tt\u003e\u003cbr\u003e\u003cbr\u003e\", \"base64\": false}]}], \"x_generator\": {\"engine\": \"Vulnogram 0.1.0-dev\"}, \"descriptions\": [{\"lang\": \"en\", \"value\": \"A Loop with Unreachable Exit Condition (\u0027Infinite Loop\u0027) 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,\\u00a0\\n  *  from 21.4 before 21.4R3-S12,\\u00a0\\n  *  from 22.4 before 22.4R3-S8,\\u00a0\\n  *  from 23.2 before 23.2R2-S5,\\u00a0\\n  *  from 23.4 before 23.4R2-S6,\\u00a0\\n  *  from 24.2 before 24.2R2-S3,\\u00a0\\n  *  from 24.4 before 24.4R2-S1,\\u00a0\\n  *  from 25.2 before 25.2R1-S1, 25.2R2.\", \"supportingMedia\": [{\"type\": \"text/html\", \"value\": \"A Loop with Unreachable Exit Condition (\u0027Infinite Loop\u0027) 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).\u003cbr\u003e\u003cbr\u003eOn 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.\u003cbr\u003e\u003cbr\u003eThis issue only occurs over TCP. SIP messages sent over UDP cannot trigger this issue.\u003cbr\u003e\u003cbr\u003e\u003cp\u003eThis issue affects Junos OS on SRX Series and MX Series with MX-SPC3 and MS-MPC:\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cul\u003e\u003cli\u003eall versions before 21.2R3-S10,\u0026nbsp;\u003c/li\u003e\u003cli\u003efrom 21.4 before 21.4R3-S12,\u0026nbsp;\u003c/li\u003e\u003cli\u003efrom 22.4 before 22.4R3-S8,\u0026nbsp;\u003c/li\u003e\u003cli\u003efrom 23.2 before 23.2R2-S5,\u0026nbsp;\u003c/li\u003e\u003cli\u003efrom 23.4 before 23.4R2-S6,\u0026nbsp;\u003c/li\u003e\u003cli\u003efrom 24.2 before 24.2R2-S3,\u0026nbsp;\u003c/li\u003e\u003cli\u003efrom 24.4 before 24.4R2-S1,\u0026nbsp;\u003c/li\u003e\u003cli\u003efrom 25.2 before 25.2R1-S1, 25.2R2.\u003c/li\u003e\u003c/ul\u003e\u003cp\u003e\u003c/p\u003e\", \"base64\": false}]}], \"problemTypes\": [{\"descriptions\": [{\"lang\": \"en\", \"type\": \"CWE\", \"cweId\": \"CWE-835\", \"description\": \"CWE-835 Loop with Unreachable Exit Condition (\u0027Infinite Loop\u0027)\"}]}], \"configurations\": [{\"lang\": \"en\", \"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 \u0027show security alg status\u0027 command:\\n\\n\\n\\nuser@junos\u003e show security alg status\\n\\nALG Status:\\n\\n...\\n\\n\\u00a0 SIP  \\u00a0 \\u00a0 : Enabled\", \"supportingMedia\": [{\"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:\u003cbr\u003e\u003cbr\u003e\\n\\n\u003ctt\u003e\u003cspan style=\\\"background-color: rgb(255, 255, 255);\\\"\u003e[security alg sip enable]\u003c/span\u003e\u003c/tt\u003e\u003cbr\u003e\\n\u003cbr\u003eOn SRX Series and MX Series with MX-SPC3, the SIP ALG status can be confirmed via the \u0027show security alg status\u0027 command:\u003cbr\u003e\\n\u003cbr\u003e\\n\u003ctt\u003euser@junos\u0026gt; show security alg status\u003c/tt\u003e\u003cbr\u003e\\n\u003ctt\u003eALG Status:\u003c/tt\u003e\u003cbr\u003e\\n...\u003cbr\u003e\\n\u003ctt\u003e\u0026nbsp; SIP  \u0026nbsp; \u0026nbsp; : Enabled\u003c/tt\u003e\u003cbr\u003e\", \"base64\": false}]}], \"providerMetadata\": {\"orgId\": \"8cbe9d5a-a066-4c94-8978-4b15efeae968\", \"shortName\": \"juniper\", \"dateUpdated\": \"2026-01-15T20:19:22.158Z\"}}}",
      "cveMetadata": "{\"cveId\": \"CVE-2026-21905\", \"state\": \"PUBLISHED\", \"dateUpdated\": \"2026-01-16T16:26:02.071Z\", \"dateReserved\": \"2026-01-05T17:32:48.710Z\", \"assignerOrgId\": \"8cbe9d5a-a066-4c94-8978-4b15efeae968\", \"datePublished\": \"2026-01-15T20:19:22.158Z\", \"assignerShortName\": \"juniper\"}",
      "dataType": "CVE_RECORD",
      "dataVersion": "5.2"
    }
  }
}


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Sightings

Author Source Type Date

Nomenclature

  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
  • Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
  • Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
  • Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
  • Not confirmed: The user expressed doubt about the validity of the vulnerability.
  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.



Detection rules are retrieved from Rulezet.