{"api_version":"1","generated_at":"2026-08-20T23:31:46+00:00","cve":"CVE-2026-63387","urls":{"html":"https://cve.report/CVE-2026-63387","api":"https://cve.report/api/cve/CVE-2026-63387.json","docs":"https://cve.report/api","cve_org":"https://www.cve.org/CVERecord?id=CVE-2026-63387","nvd":"https://nvd.nist.gov/vuln/detail/CVE-2026-63387"},"summary":{"title":"Libevent: Off-by-one stack buffer overflow in dnsname_to_labels via crafted DNS server response","description":"Libevent is an event notification library. Prior to 2.1.13 and 2.2.2-alpha, libevent has an off-by-one stack buffer overflow in evdns.c when dnsname_to_labels formats a name-bearing DNS record at the end of the 64 KB stack buffer allocated by evdns_server_request_format_response. The final-label check permits j plus label_len plus one to equal buf_len, after which the terminating null byte is written to buf[buf_len]. A crafted DNS server response containing PTR, CNAME, MX, NS, or SOA data can trigger the one-byte out-of-bounds write and crash or corrupt the process. This issue is fixed in versions 2.1.13 and 2.2.2-alpha.","state":"PUBLISHED","assigner":"GitHub_M","published_at":"2026-08-20 18:16:36","updated_at":"2026-08-20 18:16:36"},"problem_types":["CWE-121","CWE-193","CWE-787","CWE-121 CWE-121: Stack-based Buffer Overflow","CWE-193 CWE-193: Off-by-one Error","CWE-787 CWE-787: Out-of-bounds Write"],"metrics":[{"version":"3.1","source":"security-advisories@github.com","type":"Secondary","score":"7","severity":"HIGH","vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:H","data":{"version":"3.1","vectorString":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:H","baseScore":7,"baseSeverity":"HIGH","attackVector":"NETWORK","attackComplexity":"HIGH","privilegesRequired":"NONE","userInteraction":"NONE","scope":"UNCHANGED","confidentialityImpact":"LOW","integrityImpact":"LOW","availabilityImpact":"HIGH"}},{"version":"3.1","source":"CNA","type":"DECLARED","score":"7","severity":"HIGH","vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:H","data":{"attackComplexity":"HIGH","attackVector":"NETWORK","availabilityImpact":"HIGH","baseScore":7,"baseSeverity":"HIGH","confidentialityImpact":"LOW","integrityImpact":"LOW","privilegesRequired":"NONE","scope":"UNCHANGED","userInteraction":"NONE","vectorString":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:H","version":"3.1"}}],"references":[{"url":"https://github.com/libevent/libevent/security/advisories/GHSA-58rx-7448-jw47","name":"https://github.com/libevent/libevent/security/advisories/GHSA-58rx-7448-jw47","refsource":"security-advisories@github.com","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://github.com/libevent/libevent/releases/tag/release-2.1.13-stable","name":"https://github.com/libevent/libevent/releases/tag/release-2.1.13-stable","refsource":"security-advisories@github.com","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://github.com/libevent/libevent/releases/tag/release-2.2.2-alpha","name":"https://github.com/libevent/libevent/releases/tag/release-2.2.2-alpha","refsource":"security-advisories@github.com","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-63387","name":"CVE Program record","refsource":"CVE.ORG","tags":["canonical"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-63387","name":"NVD vulnerability detail","refsource":"NVD","tags":["canonical","analysis"]}],"affected":[{"source":"CNA","vendor":"libevent","product":"libevent","version":"affected >= 2.2.0-alpha, < 2.2.2-alpha","platforms":[]},{"source":"CNA","vendor":"libevent","product":"libevent","version":"affected < 2.1.13","platforms":[]}],"timeline":[],"solutions":[],"workarounds":[],"exploits":[],"credits":[],"nvd_cpes":[],"vendor_comments":[],"enrichments":{"kev":null,"epss":null,"legacy_qids":[]},"source_records":{"cve_program":{"containers":{"cna":{"affected":[{"product":"libevent","vendor":"libevent","versions":[{"status":"affected","version":">= 2.2.0-alpha, < 2.2.2-alpha"},{"status":"affected","version":"< 2.1.13"}]}],"descriptions":[{"lang":"en","value":"Libevent is an event notification library. Prior to 2.1.13 and 2.2.2-alpha, libevent has an off-by-one stack buffer overflow in evdns.c when dnsname_to_labels formats a name-bearing DNS record at the end of the 64 KB stack buffer allocated by evdns_server_request_format_response. The final-label check permits j plus label_len plus one to equal buf_len, after which the terminating null byte is written to buf[buf_len]. A crafted DNS server response containing PTR, CNAME, MX, NS, or SOA data can trigger the one-byte out-of-bounds write and crash or corrupt the process. This issue is fixed in versions 2.1.13 and 2.2.2-alpha."}],"metrics":[{"cvssV3_1":{"attackComplexity":"HIGH","attackVector":"NETWORK","availabilityImpact":"HIGH","baseScore":7,"baseSeverity":"HIGH","confidentialityImpact":"LOW","integrityImpact":"LOW","privilegesRequired":"NONE","scope":"UNCHANGED","userInteraction":"NONE","vectorString":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:H","version":"3.1"}}],"problemTypes":[{"descriptions":[{"cweId":"CWE-121","description":"CWE-121: Stack-based Buffer Overflow","lang":"en","type":"CWE"}]},{"descriptions":[{"cweId":"CWE-193","description":"CWE-193: Off-by-one Error","lang":"en","type":"CWE"}]},{"descriptions":[{"cweId":"CWE-787","description":"CWE-787: Out-of-bounds Write","lang":"en","type":"CWE"}]}],"providerMetadata":{"dateUpdated":"2026-08-20T17:53:41.863Z","orgId":"a0819718-46f1-4df5-94e2-005712e83aaa","shortName":"GitHub_M"},"references":[{"name":"https://github.com/libevent/libevent/security/advisories/GHSA-58rx-7448-jw47","tags":["x_refsource_CONFIRM"],"url":"https://github.com/libevent/libevent/security/advisories/GHSA-58rx-7448-jw47"},{"name":"https://github.com/libevent/libevent/releases/tag/release-2.1.13-stable","tags":["x_refsource_MISC"],"url":"https://github.com/libevent/libevent/releases/tag/release-2.1.13-stable"},{"name":"https://github.com/libevent/libevent/releases/tag/release-2.2.2-alpha","tags":["x_refsource_MISC"],"url":"https://github.com/libevent/libevent/releases/tag/release-2.2.2-alpha"}],"source":{"advisory":"GHSA-58rx-7448-jw47","discovery":"UNKNOWN"},"title":"Libevent: Off-by-one stack buffer overflow in dnsname_to_labels via crafted DNS server response"}},"cveMetadata":{"assignerOrgId":"a0819718-46f1-4df5-94e2-005712e83aaa","assignerShortName":"GitHub_M","cveId":"CVE-2026-63387","datePublished":"2026-08-20T17:53:41.863Z","dateReserved":"2026-07-16T17:39:30.171Z","dateUpdated":"2026-08-20T17:53:41.863Z","state":"PUBLISHED"},"dataType":"CVE_RECORD","dataVersion":"5.2"},"nvd":{"publishedDate":"2026-08-20 18:16:36","lastModifiedDate":"2026-08-20 18:16:36","problem_types":["CWE-121","CWE-193","CWE-787","CWE-121 CWE-121: Stack-based Buffer Overflow","CWE-193 CWE-193: Off-by-one Error","CWE-787 CWE-787: Out-of-bounds Write"],"metrics":{"cvssMetricV31":[{"source":"security-advisories@github.com","type":"Secondary","cvssData":{"version":"3.1","vectorString":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:H","baseScore":7,"baseSeverity":"HIGH","attackVector":"NETWORK","attackComplexity":"HIGH","privilegesRequired":"NONE","userInteraction":"NONE","scope":"UNCHANGED","confidentialityImpact":"LOW","integrityImpact":"LOW","availabilityImpact":"HIGH"},"exploitabilityScore":2.2,"impactScore":4.7}]},"configurations":[]},"legacy_mitre":{"record":{"CveYear":"2026","CveId":"63387","Ordinal":"1","Title":"Libevent: Off-by-one stack buffer overflow in dnsname_to_labels ","CVE":"CVE-2026-63387","Year":"2026"},"notes":[{"CveYear":"2026","CveId":"63387","Ordinal":"1","NoteData":"Libevent is an event notification library. Prior to 2.1.13 and 2.2.2-alpha, libevent has an off-by-one stack buffer overflow in evdns.c when dnsname_to_labels formats a name-bearing DNS record at the end of the 64 KB stack buffer allocated by evdns_server_request_format_response. The final-label check permits j plus label_len plus one to equal buf_len, after which the terminating null byte is written to buf[buf_len]. A crafted DNS server response containing PTR, CNAME, MX, NS, or SOA data can trigger the one-byte out-of-bounds write and crash or corrupt the process. This issue is fixed in versions 2.1.13 and 2.2.2-alpha.","Type":"Description","Title":"Libevent: Off-by-one stack buffer overflow in dnsname_to_labels "}]}}}