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Message-ID: <49ccdfbc-8518-4e9f-9e2a-b9837af147d1@oracle.com>
Date: Fri, 4 Oct 2024 14:17:44 -0700
From: Alan Coopersmith <alan.coopersmith@...cle.com>
To: oss-security@...ts.openwall.com
Subject: CVE-2024-8508 in Unbound DNS server prior to 1.21.1
https://nlnetlabs.nl/downloads/unbound/CVE-2024-8508.txt states:
> The CVE number for this vulnerability is CVE-2024-8508.
>
> A vulnerability has been discovered in Unbound when handling replies
> with very large RRsets that Unbound needs to perform name compression
> for.
>
>
> == Summary
> 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.
>
> Unbound 1.21.1 includes a fix to limit time spent on name compression.
>
>
> == Affected products
> Unbound up to and including 1.21.0.
>
>
> == Description
> 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.
>
>
> == Solution
> Apply the attached patch using:
>
> patch -p1 < patch_CVE-2024-8508.diff
>
> then run 'make install' to install Unbound.
>
> The patch is tested to work on Unbound 1.21.0.
>
>
> == Acknowledgments
> We would like to thank Toshifumi Sakaguchi for discovering and
> responsibly disclosing the vulnerability.
The patch is available from
https://nlnetlabs.nl/downloads/unbound/patch_CVE-2024-8508.diff
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