{"id":"DEBIAN-CVE-2026-78227","details":"NLnet Labs Unbound 1.22.0 up to and including 1.26.1, has a use-after-free vulnerability when compiled for DNS-over-QUIC support with '--with-libngtcp2'. Each DoQ stream owns an output buffer that holds the DNS response. ngtcp2's retransmission buffer keeps a shallow pointer into the output buffer for as long as a STREAM frame may be resent. On a client RESET_STREAM, the output buffer is freed but ngtcp2 still holds the matching retransmission entries. The next PTO timeout makes ngtcp2 re-encode the STREAM frame and copy from the freed buffer. A malicious actor that can query Unbound over DoQ and that withholds ACKs, sends RESET_STREAM, and waits for PTO, reaches this use-after-free with no privilege. This leads to retransmissions against freed memory and eventually an abnormal server exit under a 20-query spray.","modified":"2026-09-24T08:47:31.640566588Z","published":"2026-09-16T09:17:05.987Z","upstream":["CVE-2026-78227"],"references":[{"type":"ADVISORY","url":"https://security-tracker.debian.org/tracker/CVE-2026-78227"}],"affected":[{"package":{"name":"unbound","ecosystem":"Debian:12","purl":"pkg:deb/debian/unbound?arch=source&distro=bookworm"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["1.17.1-2","1.17.1-2+deb12u1","1.17.1-2+deb12u2","1.17.1-2+deb12u3","1.17.1-2+deb12u4","1.17.1-2+loong64","1.18.0-1","1.18.0-2","1.19.1-1","1.19.2-1","1.20.0-1","1.21.1-1","1.22.0-1","1.22.0-2","1.23.1-1","1.24.0-1","1.24.0-2","1.24.1-1","1.24.1-2","1.24.2-1","1.25.0-1","1.25.1-1","1.25.2-1","1.26.0-1","1.26.0-2","1.26.1-1"],"ecosystem_specific":{"urgency":"not yet assigned"},"database_specific":{"source":"https://storage.googleapis.com/osv-test-debian-osv/debian-cve-osv/DEBIAN-CVE-2026-78227.json"}},{"package":{"name":"unbound","ecosystem":"Debian:13","purl":"pkg:deb/debian/unbound?arch=source&distro=trixie"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"1.26.1-0+deb13u1"}]}],"versions":["1.22.0-2","1.22.0-2+deb13u1","1.22.0-2+deb13u2","1.22.0-2+deb13u3","1.23.1-1","1.24.0-1","1.24.0-2","1.24.1-1","1.24.1-2","1.24.2-1","1.25.0-1","1.25.1-1","1.25.2-1","1.26.0-1","1.26.0-2"],"ecosystem_specific":{"urgency":"not yet assigned"},"database_specific":{"source":"https://storage.googleapis.com/osv-test-debian-osv/debian-cve-osv/DEBIAN-CVE-2026-78227.json"}},{"package":{"name":"unbound","ecosystem":"Debian:14","purl":"pkg:deb/debian/unbound?arch=source&distro=forky"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"1.26.1-1"}]}],"versions":["1.22.0-2","1.23.1-1","1.24.0-1","1.24.0-2","1.24.1-1","1.24.1-2","1.24.2-1","1.25.0-1","1.25.1-1","1.25.2-1","1.26.0-1","1.26.0-2"],"ecosystem_specific":{"urgency":"not yet assigned"},"database_specific":{"source":"https://storage.googleapis.com/osv-test-debian-osv/debian-cve-osv/DEBIAN-CVE-2026-78227.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:L"}]}