Use-after-free in Unbound - CVE-2026-82720

Vulnerability identifier: #VU150195

CSH Severity: Medium

CVSS v4: 8.2 [CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N]

CVE-ID: CVE-2026-82720

CWE-ID: CWE-416

Exploitation vector: Remote access

Exploit availability: No public exploit available

The vulnerability allows a remote attacker to cause a denial of service.

The vulnerability exists due to use-after-free in DNS-over-HTTPS stream handling when processing dropped streams during failure code paths. A remote attacker can send appropriate traffic over a single DNS-over-HTTPS connection to terminate the process.

The issue affects builds compiled with DNS-over-HTTPS support using --with-libnghttp2 and requires an RPZ drop query or heavy client traffic.

Unbound
SUSE Linux Enterprise Server 15 SP6
SUSE Linux Enterprise Server 15 SP4
SUSE Linux Enterprise Server 15 SP5
Debian Linux
SUSE Linux Enterprise High Performance Computing 15
SUSE Linux Enterprise High Performance Computing ESPOS 15
SUSE Linux Enterprise High Performance Computing LTSS 15
SUSE Linux Enterprise Server 15
SUSE Linux Enterprise Server for SAP Applications 15
SUSE Linux Enterprise Desktop 15
SUSE Linux Enterprise Real Time 15
SUSE Linux Enterprise Micro
Basesystem Module
SUSE Package Hub 15
openSUSE Leap
Anolis OS
Fedora
unbound-utils
unbound-libs
unbound-devel
unbound-anchor
unbound
python3-unbound
libunbound8
unbound-debugsource
unbound-anchor-debuginfo
unbound-debuginfo
libunbound8-debuginfo
unbound-python-debuginfo
unbound-munin
libunbound-devel-mini-debuginfo
unbound-python
libunbound-devel-mini-debugsource
libunbound-devel-mini
unbound (Debian package)

Install security update from vendor's website.

Unbound - update to 1.26.1
unbound-utils - update to 1.17.1-21
unbound-libs - update to 1.17.1-21
unbound-devel - update to 1.17.1-21
unbound-anchor - update to 1.17.1-21
unbound - update to 1.17.1-21
python3-unbound - update to 1.17.1-21
unbound - addressed in versions 1.26.1-1.fc43, 1.26.1-1.fc44, 1.26.1-1.fc45
libunbound8 - addressed in versions 1.26.1-150100.10.31.1, 1.26.1-150600.23.24.1
unbound-debugsource - addressed in versions 1.26.1-150100.10.31.1, 1.26.1-150600.23.24.1
unbound-anchor-debuginfo - addressed in versions 1.26.1-150100.10.31.1, 1.26.1-150600.23.24.1
unbound-anchor - addressed in versions 1.26.1-150100.10.31.1, 1.26.1-150600.23.24.1
unbound-debuginfo - addressed in versions 1.26.1-150100.10.31.1, 1.26.1-150600.23.24.1
unbound-devel - addressed in versions 1.26.1-150100.10.31.1, 1.26.1-150600.23.24.1
libunbound8-debuginfo - addressed in versions 1.26.1-150100.10.31.1, 1.26.1-150600.23.24.1
unbound-python-debuginfo - update to 1.26.1-150600.23.24.1
unbound-munin - update to 1.26.1-150600.23.24.1
libunbound-devel-mini-debuginfo - update to 1.26.1-150600.23.24.1
unbound-python - update to 1.26.1-150600.23.24.1
libunbound-devel-mini-debugsource - update to 1.26.1-150600.23.24.1
unbound - update to 1.26.1-150600.23.24.1
libunbound-devel-mini - update to 1.26.1-150600.23.24.1
unbound (Debian package) - update to 1.26.1-0+deb13u1

• https://www.nlnetlabs.nl/downloads/unbound/CVE-2026-82720.txt
• https://github.com/NLnetLabs/unbound/releases/tag/release-1.26.1

• Multiple vulnerabilities in Unbound
• Fedora 45 update for unbound
• Fedora 44 update for unbound
• Fedora 43 update for unbound
• Debian update for unbound
• SUSE update for unbound
• SUSE update for unbound
• Anolis OS update for unbound