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        "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": "2026-07-22T14:07:31.075Z"
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    "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"
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            "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."
                }
            ],
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                        "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"
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                            "lang": "en",
                            "cweId": "CWE-476",
                            "description": "CWE-476: NULL Pointer Dereference",
                            "type": "CWE"
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            ],
            "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"
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                {
                    "time": "2026-05-27T00:00:00.000Z",
                    "lang": "en",
                    "value": "Issue reported by Xin Wang"
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                    "time": "2026-05-27T00:00:00.000Z",
                    "lang": "en",
                    "value": "NLnet Labs shares patch with Xin Wang"
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                {
                    "time": "2026-05-27T00:00:00.000Z",
                    "lang": "en",
                    "value": "Xin Wang verifies patch"
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                {
                    "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"
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                    "time": "2026-07-22T00:00:00.000Z",
                    "lang": "en",
                    "value": "Fixes released with version 1.25.2"
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            "credits": [
                {
                    "lang": "en",
                    "value": "Qifan Zhang (Palo Alto Networks)",
                    "type": "finder"
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                {
                    "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"
                    ]
                }
            ],
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                "orgId": "206fc3a0-e175-490b-9eaa-a5738056c9f6",
                "shortName": "NLnet Labs",
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