{"dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": {"cveId": "CVE-2026-55717", "assignerOrgId": "206fc3a0-e175-490b-9eaa-a5738056c9f6", "state": "PUBLISHED", "assignerShortName": "NLnet Labs", "dateReserved": "2026-06-22T12:27:22.813Z", "datePublished": "2026-07-22T13:09:40.927Z", "dateUpdated": "2026-07-22T13:09:40.927Z"}, "containers": {"cna": {"title": "'serve-expired-client-timeout' and 'response-ip' CNAME redirect could lead to a crash", "datePublic": "2026-07-22T00:00:00.000Z", "affected": [{"vendor": "NLnet Labs", "product": "Unbound", "versions": [{"version": "1.10.0", "status": "affected", "lessThan": "1.25.2", "versionType": "semver"}], "defaultStatus": "unaffected"}], "descriptions": [{"lang": "en", "value": "In NLnet Labs Unbound 1.10.0 up to and including 1.25.1, when 'serve-expired: yes' is set together with a 'response-ip: <net> redirect' /'response-ip-data: <net> CNAME <target>' rule (or the RPZ 'rpz-cname-override' equivalent), a remote client who controls any delegated domain can crash the daemon. The serve-expired-client-timeout callback runs a two-pass loop to chase the respip-generated CNAME alias; on the second pass it resets 'alias_rrset' but not 'partial_rep'. Later, this inconsistency leads to a NULL pointer dereference and an eventual crash. A malicious actor can exploit the vulnerability by controlling any zone that replies with an A/AAAA record that falls inside the configured response-ip/rpz subnet. By delaying the answer when the previous record has expired, the vulnerable path of 'serve-expired-client-timeout' is taken leading to denial of service via the server crash."}], "metrics": [{"format": "CVSS", "scenarios": [{"lang": "en", "value": "GENERAL"}], "cvssV3_1": {"version": "3.1", "baseScore": 5.9, "baseSeverity": "MEDIUM", "vectorString": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H"}}], "problemTypes": [{"descriptions": [{"lang": "en", "cweId": "CWE-476", "description": "CWE-476: NULL Pointer Dereference", "type": "CWE"}]}], "solutions": [{"lang": "en", "value": "This issue is fixed starting with version 1.25.2"}], "timeline": [{"time": "2026-05-05T00:00:00.000Z", "lang": "en", "value": "Issue reported by Qifan Zhang"}, {"time": "2026-05-27T00:00:00.000Z", "lang": "en", "value": "Issue reported by Xin Wang"}, {"time": "2026-05-27T00:00:00.000Z", "lang": "en", "value": "NLnet Labs shares patch with Xin Wang"}, {"time": "2026-05-27T00:00:00.000Z", "lang": "en", "value": "Xin Wang verifies patch"}, {"time": "2026-05-29T00:00:00.000Z", "lang": "en", "value": "NLnet Labs shares patch with Qifan Zhang"}, {"time": "2026-06-03T00:00:00.000Z", "lang": "en", "value": "Qifan Zhang verifies patch"}, {"time": "2026-07-22T00:00:00.000Z", "lang": "en", "value": "Fixes released with version 1.25.2"}], "credits": [{"lang": "en", "value": "Qifan Zhang (Palo Alto Networks)", "type": "finder"}, {"lang": "en", "value": "Xin Wang (Northwestern Polytechnical University)", "type": "finder"}, {"lang": "en", "value": "Jiapeng Li (Northwestern Polytechnical University)", "type": "finder"}, {"lang": "en", "value": "Jiajia Liu (Northwestern Polytechnical University)", "type": "finder"}], "references": [{"url": "https://www.nlnetlabs.nl/downloads/unbound/CVE-2026-55717.txt", "tags": ["vendor-advisory"]}], "providerMetadata": {"orgId": "206fc3a0-e175-490b-9eaa-a5738056c9f6", "shortName": "NLnet Labs", "dateUpdated": "2026-07-22T13:09:40.927Z"}, "x_generator": {"engine": "cvelib 1.8.0"}}}}

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