CVE-2024-8508

NameCVE-2024-8508
DescriptionNLnet Labs Unbound up to and including version 1.21.0 contains a vulnerability when handling replies with very large RRsets that it needs to perform name compression for. Malicious upstreams responses with very large RRsets can cause Unbound to spend a considerable time applying name compression to downstream replies. This can lead to degraded performance and eventually denial of service in well orchestrated attacks. The vulnerability can be exploited by a malicious actor querying Unbound for the specially crafted contents of a malicious zone with very large RRsets. Before Unbound replies to the query it will try to apply name compression which was an unbounded operation that could lock the CPU until the whole packet was complete. Unbound version 1.21.1 introduces a hard limit on the number of name compression calculations it is willing to do per packet. Packets that need more compression will result in semi-compressed packets or truncated packets, even on TCP for huge messages, to avoid locking the CPU for long. This change should not affect normal DNS traffic.
SourceCVE (at NVD; CERT, LWN, oss-sec, fulldisc, Red Hat, Ubuntu, Gentoo, SUSE bugzilla/CVE, GitHub advisories/code/issues, web search, more)
ReferencesDLA-3952-1, ELA-1235-1, ELA-1255-1
Debian Bugs1083282

Vulnerable and fixed packages

The table below lists information on source packages.

Source PackageReleaseVersionStatus
unbound (PTS)jessie, jessie (lts)1.4.22-3+deb8u4vulnerable
stretch1.6.0-3+deb9u2vulnerable
buster, buster (lts)1.9.0-2+deb10u5fixed
buster (security)1.9.0-2+deb10u4vulnerable
bullseye1.13.1-1+deb11u2vulnerable
bullseye (security)1.13.1-1+deb11u4fixed
bookworm (security), bookworm1.17.1-2+deb12u2vulnerable
sid, trixie1.22.0-1fixed
unbound1.9 (PTS)stretch (security)1.9.0-2+deb10u2~deb9u2vulnerable
stretch (lts), stretch1.9.0-2+deb10u2~deb9u5fixed

The information below is based on the following data on fixed versions.

PackageTypeReleaseFixed VersionUrgencyOriginDebian Bugs
unboundsourcejessie(unfixed)end-of-life
unboundsourcestretch(unfixed)end-of-life
unboundsourcebuster1.9.0-2+deb10u5ELA-1235-1
unboundsourcebullseye1.13.1-1+deb11u4DLA-3952-1
unboundsource(unstable)1.21.1-11083282
unbound1.9sourcestretch1.9.0-2+deb10u2~deb9u5ELA-1255-1
unbound1.9source(unstable)(unfixed)

Notes

[bookworm] - unbound <no-dsa> (Minor issue)
Advisory: https://nlnetlabs.nl/downloads/unbound/CVE-2024-8508.txt
Patch: https://nlnetlabs.nl/downloads/unbound/patch_CVE-2024-8508.diff
Fixed by: https://github.com/NLnetLabs/unbound/commit/b7c61d7cc256d6a174e6179622c7fa968272c259 (release-1.21.1)

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