CVE-2026-80225 PUBLISHED

Possible degradation of service from continuous queries on the same TCP/DoT connection

Assigner: NLnet Labs
Reserved: 07.09.2026 Published: 16.09.2026 Updated: 16.09.2026

In NLnetLabs Unbound up to and including 1.26.0, a degradation of service vulnerability is present in the TCP/DoT reading procedure where there is no limit on consecutive reads. A malicious actor that can stream and sustain a rate of distinct uncached names over the TCP/DoT connection, monopolizes a single worker's entire event loop for as long as its writes stay ahead of the drain.

Metrics

CVSS 3.1

CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
CVSS Score: 5.3

Attack Vector	Network	Scope	Unchanged
Attack Complexity	Low	Confidentiality Impact	None
Privileges Required	None	Integrity Impact	None
User Interaction	None	Availability Impact	Low

CVSS 3.1

Product Status

Vendor	NLnet Labs
Product	Unbound
Versions	Default: unaffected affected from 0 to 1.26.1 (excl.)

Solutions

This issue is fixed starting with version 1.26.1

Credits

Qifan Zhang (Palo Alto Networks) finder

References

https://www.nlnetlabs.nl/downloads/unbound/CVE-2026-80225.txt

Problem Types

CWE-770: Allocation of Resources Without Limits or Throttling CWE