{"id":"CVE-2026-21920","state":"PUBLISHED","title":"Junos OS: SRX Series: If a specific request is processed by the DNS subsystem flowd will crash","description":"An Unchecked Return Value vulnerability in the DNS module of Juniper Networks Junos OS on SRX Series allows an unauthenticated, network-based attacker to cause a Denial-of-Service (DoS).\n\n\n\n\nIf an SRX Series device configured for DNS processing, receives a specifically formatted DNS request flowd will crash and restart, which causes a service interruption until the process has recovered.\n\nThis issue affects Junos OS on SRX Series:\n\n\n\n  *  23.4 versions before 23.4R2-S5,\n  *  24.2 versions before 24.2R2-S1,\n  *  24.4 versions before 24.4R2.\n\n\n\n\n\n\nThis issue does not affect Junos OS versions before 23.4R1.","publishedAt":"2026-01-15T20:28:10.526Z","updatedAt":"2026-01-15T20:59:21.070Z","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/RE:M","source":"juniper"},"assigner":"juniper","products":["Juniper Networks Junos OS"],"affected":[{"vendor":"Juniper Networks","product":"Junos OS","defaultStatus":"unaffected","versions":[{"version":"23.4","status":"affected","lessThan":"23.4R2-S5","versionType":"semver"},{"version":"24.2","status":"affected","lessThan":"24.2R2-S1","versionType":"semver"},{"version":"24.4","status":"affected","lessThan":"24.4R2","versionType":"semver"},{"version":"0","status":"unaffected","lessThan":"23.4R1","versionType":"semver"}],"platforms":["SRX Series"]}],"references":["https://supportportal.juniper.net/JSA106020","https://kb.juniper.net/JSA106020"],"weaknesses":["CWE-252"],"ingestedAt":"2026-10-29T20:11:10.572Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/21xxx/CVE-2026-21920.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-21920","state":"PUBLISHED","datePublished":"2026-01-15T20:28:10.526Z","dateUpdated":"2026-01-15T20:59:21.070Z","assignerShortName":"juniper","assignerOrgId":"8cbe9d5a-a066-4c94-8978-4b15efeae968","dateReserved":"2026-01-05T17:32:48.712Z"},"containers":{"cna":{"title":"Junos OS: SRX Series: If a specific request is processed by the DNS subsystem flowd will crash","descriptions":[{"lang":"en","value":"An Unchecked Return Value vulnerability in the DNS module of Juniper Networks Junos OS on SRX Series allows an unauthenticated, network-based attacker to cause a Denial-of-Service (DoS).\n\n\n\n\nIf an SRX Series device configured for DNS processing, receives a specifically formatted DNS request flowd will crash and restart, which causes a service interruption until the process has recovered.\n\nThis issue affects Junos OS on SRX Series:\n\n\n\n  *  23.4 versions before 23.4R2-S5,\n  *  24.2 versions before 24.2R2-S1,\n  *  24.4 versions before 24.4R2.\n\n\n\n\n\n\nThis issue does not affect Junos OS versions before 23.4R1."}],"affected":[{"vendor":"Juniper Networks","product":"Junos OS","defaultStatus":"unaffected","versions":[{"version":"23.4","status":"affected","lessThan":"23.4R2-S5","versionType":"semver"},{"version":"24.2","status":"affected","lessThan":"24.2R2-S1","versionType":"semver"},{"version":"24.4","status":"affected","lessThan":"24.4R2","versionType":"semver"},{"version":"0","status":"unaffected","lessThan":"23.4R1","versionType":"semver"}],"platforms":["SRX Series"]}],"references":[{"url":"https://supportportal.juniper.net/JSA106020","tags":["vendor-advisory"]},{"url":"https://kb.juniper.net/JSA106020","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":"NOT_DEFINED","subAvailabilityImpact":"LOW","subConfidentialityImpact":"NONE","subIntegrityImpact":"NONE","userInteraction":"NONE","valueDensity":"NOT_DEFINED","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/RE:M","version":"4.0","vulnAvailabilityImpact":"HIGH","vulnConfidentialityImpact":"NONE","vulnIntegrityImpact":"NONE","vulnerabilityResponseEffort":"MODERATE"},"format":"CVSS","scenarios":[{"lang":"en","value":"GENERAL"}]}],"problemTypes":[{"descriptions":[{"cweId":"CWE-252","description":"CWE-252 Unchecked Return Value","lang":"en","type":"CWE"}]}],"providerMetadata":{"shortName":"juniper","orgId":"8cbe9d5a-a066-4c94-8978-4b15efeae968","dateUpdated":"2026-01-15T20:28:10.526Z"},"configurations":[{"lang":"en","supportingMedia":[{"base64":false,"type":"text/html","value":"<span style=\"background-color: rgb(255, 255, 255);\">A device is exposed to this issue when one of the following features are used / configurations are present:<br><br>- GeoIP:<br></span><tt><tt><tt></tt><br><tt><span style=\"background-color: rgb(255, 255, 255);\">[ security dynamic-address address-name &lt;name&gt; profile category GeoIP ... ]<br></span></tt></tt></tt><br><br>- DNS security:<br><br><tt><tt><tt><span style=\"background-color: rgb(255, 255, 255);\">[&nbsp;services security-metadata-streaming policy &lt;name&gt; dns detections ... ]<br><br>or<br><br>[ services security-intelligence profile &lt;profile-name&gt; category DNS ]<br>[ services security-intelligence profile policy &lt;policy-name&gt; DNS &lt;profile-name&gt; ]<br></span></tt><tt><tt><tt><br><tt>\n\n</tt></tt></tt><tt></tt><tt></tt><tt></tt><tt></tt><tt></tt><tt></tt></tt></tt></tt><tt></tt>"}],"value":"A device is exposed to this issue when one of the following features are used / configurations are present:\n\n- GeoIP:\n\n[ security dynamic-address address-name <name> profile category GeoIP ... ]\n\n\n- DNS security:\n\n[ services security-metadata-streaming policy <name> dns detections ... ]\n\nor\n\n[ services security-intelligence profile <profile-name> category DNS ]\n[ services security-intelligence profile policy <policy-name> DNS <profile-name> ]"}],"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: 23.4R2-S5, 24.2R2-S1, 24.4R2, 24.4R2-S1, 25.2R1, and all subsequent releases."}],"value":"The following software releases have been updated to resolve this specific issue: 23.4R2-S5, 24.2R2-S1, 24.4R2, 24.4R2-S1, 25.2R1, and all subsequent releases."}],"source":{"advisory":"JSA106020","defect":["1851909"],"discovery":"USER"},"workarounds":[{"lang":"en","supportingMedia":[{"base64":false,"type":"text/html","value":"There are no known workarounds for this issue."}],"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":"2026-01-15T20:58:50.543674Z","id":"CVE-2026-21920","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":"2026-01-15T20:59:21.070Z"}}]}}}