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CVE-2026-78227 on Cyberus Linux 26.05

Aliases: CVE-2026-78227

Packages: unbound

Status: In Progress

Advisory Information

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.

Updates

2026-09-22 11:14 CEST

Metadata changes:

  • Status for package unbound: “In Progress”

2026-09-22 11:07 CEST

Metadata changes:

  • Status for package unbound: “New”