{"id":"UBUNTU-CVE-2026-63387","details":"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.","modified":"2026-09-02T19:41:09.410927651Z","published":"2026-08-20T18:16:00Z","upstream":["CVE-2026-63387"],"references":[{"type":"REPORT","url":"https://ubuntu.com/security/CVE-2026-63387"},{"type":"REPORT","url":"https://www.cve.org/CVERecord?id=CVE-2026-63387"}],"affected":[{"package":{"name":"libevent","ecosystem":"Ubuntu:Pro:14.04:LTS","purl":"pkg:deb/ubuntu/libevent?arch=source&distro=esm-infra-legacy%2Ftrusty"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["2.0.21-stable-1","2.0.21-stable-1ubuntu1","2.0.21-stable-1ubuntu1.14.04.1","2.0.21-stable-1ubuntu1.14.04.2","2.0.21-stable-1ubuntu1.14.04.2+esm1"],"ecosystem_specific":{"binaries":[{"binary_name":"libevent-2.0-5","binary_version":"2.0.21-stable-1ubuntu1.14.04.2+esm1"},{"binary_name":"libevent-core-2.0-5","binary_version":"2.0.21-stable-1ubuntu1.14.04.2+esm1"},{"binary_name":"libevent-extra-2.0-5","binary_version":"2.0.21-stable-1ubuntu1.14.04.2+esm1"},{"binary_name":"libevent-openssl-2.0-5","binary_version":"2.0.21-stable-1ubuntu1.14.04.2+esm1"},{"binary_version":"2.0.21-stable-1ubuntu1.14.04.2+esm1","binary_name":"libevent-pthreads-2.0-5"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-63387.json"}},{"package":{"name":"libevent","ecosystem":"Ubuntu:Pro:16.04:LTS","purl":"pkg:deb/ubuntu/libevent?arch=source&distro=esm-infra-legacy%2Fxenial"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["2.0.21-stable-2","2.0.21-stable-2ubuntu0.16.04.1","2.0.21-stable-2ubuntu0.16.04.1+esm1"],"ecosystem_specific":{"binaries":[{"binary_version":"2.0.21-stable-2ubuntu0.16.04.1+esm1","binary_name":"libevent-2.0-5"},{"binary_version":"2.0.21-stable-2ubuntu0.16.04.1+esm1","binary_name":"libevent-core-2.0-5"},{"binary_version":"2.0.21-stable-2ubuntu0.16.04.1+esm1","binary_name":"libevent-extra-2.0-5"},{"binary_name":"libevent-openssl-2.0-5","binary_version":"2.0.21-stable-2ubuntu0.16.04.1+esm1"},{"binary_name":"libevent-pthreads-2.0-5","binary_version":"2.0.21-stable-2ubuntu0.16.04.1+esm1"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-63387.json"}},{"package":{"name":"libevent","ecosystem":"Ubuntu:Pro:18.04:LTS","purl":"pkg:deb/ubuntu/libevent?arch=source&distro=esm-infra%2Fbionic"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["2.1.8-stable-4","2.1.8-stable-4build1","2.1.8-stable-4ubuntu0.1~esm1"],"ecosystem_specific":{"binaries":[{"binary_name":"libevent-2.1-6","binary_version":"2.1.8-stable-4ubuntu0.1~esm1"},{"binary_version":"2.1.8-stable-4ubuntu0.1~esm1","binary_name":"libevent-core-2.1-6"},{"binary_version":"2.1.8-stable-4ubuntu0.1~esm1","binary_name":"libevent-extra-2.1-6"},{"binary_version":"2.1.8-stable-4ubuntu0.1~esm1","binary_name":"libevent-openssl-2.1-6"},{"binary_name":"libevent-pthreads-2.1-6","binary_version":"2.1.8-stable-4ubuntu0.1~esm1"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-63387.json"}},{"package":{"name":"libevent","ecosystem":"Ubuntu:Pro:20.04:LTS","purl":"pkg:deb/ubuntu/libevent?arch=source&distro=esm-infra%2Ffocal"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["2.1.8-stable-4build1","2.1.11-stable-1~exp0","2.1.11-stable-1","2.1.11-stable-1ubuntu0.1~esm1"],"ecosystem_specific":{"binaries":[{"binary_version":"2.1.11-stable-1ubuntu0.1~esm1","binary_name":"libevent-2.1-7"},{"binary_version":"2.1.11-stable-1ubuntu0.1~esm1","binary_name":"libevent-core-2.1-7"},{"binary_name":"libevent-extra-2.1-7","binary_version":"2.1.11-stable-1ubuntu0.1~esm1"},{"binary_name":"libevent-openssl-2.1-7","binary_version":"2.1.11-stable-1ubuntu0.1~esm1"},{"binary_version":"2.1.11-stable-1ubuntu0.1~esm1","binary_name":"libevent-pthreads-2.1-7"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-63387.json"}},{"package":{"name":"libevent","ecosystem":"Ubuntu:22.04:LTS","purl":"pkg:deb/ubuntu/libevent?arch=source&distro=jammy"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["2.1.12-stable-1","2.1.12-stable-1build1","2.1.12-stable-1build2","2.1.12-stable-1build3","2.1.12-stable-1ubuntu0.1"],"ecosystem_specific":{"binaries":[{"binary_name":"libevent-2.1-7","binary_version":"2.1.12-stable-1ubuntu0.1"},{"binary_name":"libevent-core-2.1-7","binary_version":"2.1.12-stable-1ubuntu0.1"},{"binary_name":"libevent-extra-2.1-7","binary_version":"2.1.12-stable-1ubuntu0.1"},{"binary_name":"libevent-openssl-2.1-7","binary_version":"2.1.12-stable-1ubuntu0.1"},{"binary_name":"libevent-pthreads-2.1-7","binary_version":"2.1.12-stable-1ubuntu0.1"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-63387.json"}},{"package":{"name":"libevent","ecosystem":"Ubu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