7.5 HIGH
- CVSS version (CVSS): 3.1
- Attack Vector (AV): Network (N)
- Attack Complexity (AC): Low (L)
- Privileges Required (PR): None (N)
- User Interaction (UI): None (N)
- Scope (S): Unchanged (U)
- Confidentiality (C): None (N)
- Integrity (I): None (N)
- Availability (A): High (H)
- Modified Attack Vector (MAV): Network (N)
- Modified Attack Complexity (MAC): Low (L)
- Modified Privileges Required (MPR): None (N)
- Modified User Interaction (MUI): None (N)
- Modified Confidentiality (MC): None (N)
- Modified Scope (MS): Unchanged (U)
- Modified Integrity (MI): None (N)
- Modified Availability (MA): High (H)
Activity log
- Created suggestion
Remote DNS-over-QUIC denial of service due to `quic-size` budget bypass
In NLnet Labs Unbound 1.22.0 up to and including 1.25.1, when downstream DNS-over-QUIC (DoQ) is enabled, the first two bidirectional streams on a new QUIC connection (stream_id 0 and 4) bypass the per-stream 'quic-size' gate entirely, and large input buffers are allocated later, after only the 2-byte length prefix has been received from the initial streams. As a result, a remote client can make Unbound exceed the configured 'quic-size' limit with low-cost input. Using only one connection and two streams, each sending a declared 65535-byte length prefix and then holding the streams open, a client can already trivially make Unbound roughly allocate double that amount. This is a remote availability issue / memory-accounting bypass in the downstream DoQ implementation that leads to denial of service for new DoQ clients. This vulnerability needs Unbound to be compiled with DoQ support ('--with-libngtcp2') and the 'quic-port' to be configured for the listening interfaces.
References
-
https://www.nlnetlabs.nl/downloads/unbound/CVE-2026-32665.txt vendor-advisory
Affected products
- <1.25.2
Matching in nixpkgs
pkgs.unbound
Validating, recursive, and caching DNS resolver
pkgs.unbound-full
Validating, recursive, and caching DNS resolver
pkgs.unbound-with-systemd
Validating, recursive, and caching DNS resolver
pkgs.luaPackages.luaunbound
A binding to libunbound
pkgs.lua51Packages.luaunbound
A binding to libunbound
pkgs.lua52Packages.luaunbound
A binding to libunbound
pkgs.lua53Packages.luaunbound
A binding to libunbound
pkgs.lua54Packages.luaunbound
A binding to libunbound
pkgs.lua55Packages.luaunbound
A binding to libunbound
pkgs.luajitPackages.luaunbound
A binding to libunbound
pkgs.prometheus-unbound-exporter
Prometheus exporter for Unbound DNS resolver
pkgs.python313Packages.pyunbound
Python library for Unbound, the validating, recursive, and caching DNS resolver
pkgs.python314Packages.pyunbound
Python library for Unbound, the validating, recursive, and caching DNS resolver
pkgs.haskellPackages.unbound-generics
Support for programming with names and binders using GHC Generics
pkgs.haskellPackages.unbounded-delays
Unbounded thread delays and timeouts
pkgs.haskellPackages.unbound-kind-generics
Support for programming with names and binders using kind-generics
Package maintainers
-
@mweinelt Martin Weinelt <hexa@darmstadt.ccc.de>
-
@Scrumplex Sefa Eyeoglu <contact@scrumplex.net>