CVE-2026-78227 Affecting libunbound8 package, versions <1.26.1-150100.10.31.1


Severity

Recommended
0.0
high
0
10

Based on SUSE Linux Enterprise Server security rating.

Threat Intelligence

EPSS
0.34% (25th percentile)

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  • Snyk IDSNYK-SLES155-LIBUNBOUND8-20876358
  • published13 Oct 2026
  • disclosed12 Oct 2026

Introduced: 12 Oct 2026

NewCVE-2026-78227  (opens in a new tab)

How to fix?

Upgrade SLES:15.5 libunbound8 to version 1.26.1-150100.10.31.1 or higher.

NVD Description

Note: Versions mentioned in the description apply only to the upstream libunbound8 package and not the libunbound8 package as distributed by SLES. See How to fix? for SLES:15.5 relevant fixed versions and status.

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.

CVSS Base Scores

version 3.1