CVE-2024-8508
Unbounded name compression could lead to Denial of Service
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Unbounded name compression could lead to Denial of Service
NLnet 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.
Reserved 2024-09-06 | Published 2024-10-03 | Updated 2024-11-14 | Assigner NLnet LabsCWE-606: Unchecked Input for Loop Condition
| 2024-07-25: | Issue reported by Toshifumi Sakaguchi |
| 2024-07-31: | Issue acknowledged by NLnet Labs; mitigation shared with Toshifumi Sakaguchi |
| 2024-08-01: | Mitigation confirmed by Toshifumi Sakaguchi |
| 2024-10-03: | Fixes released with Unbound 1.21.1 |
Toshifumi Sakaguchi
www.nlnetlabs.nl/downloads/unbound/CVE-2024-8508.txt
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