Resource Exhaustion Affecting unbound-utils-debuginfo package, versions <0:1.17.1-1.amzn2023.0.12


Severity

Recommended
high

Based on Amazon Linux security rating.

Threat Intelligence

EPSS
0.06% (18th percentile)

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  • Snyk IDSNYK-AMZN2023-UNBOUNDUTILSDEBUGINFO-16887869
  • published27 May 2026
  • disclosed20 May 2026

Introduced: 20 May 2026

NewCVE-2026-42923  (opens in a new tab)
CWE-400  (opens in a new tab)

How to fix?

Upgrade Amazon-Linux:2023 unbound-utils-debuginfo to version 0:1.17.1-1.amzn2023.0.12 or higher.
This issue was patched in ALAS2023-2026-1756.

NVD Description

Note: Versions mentioned in the description apply only to the upstream unbound-utils-debuginfo package and not the unbound-utils-debuginfo package as distributed by Amazon-Linux. See How to fix? for Amazon-Linux:2023 relevant fixed versions and status.

NLnet Labs Unbound up to and including version 1.25.0 has a vulnerability in the DNSSEC validator where the code path to consult the negative cache for DS records does not take into account the limit on NSEC3 hash calculations introduced in 1.19.1. This leads to degradation of service during the attack. An adversary that controls a DNSSEC signed zone can exploit this by signing NSEC3 records with acceptably high iterations for child delegations and querying a vulnerable Unbound. Unbound will keep performing the allowed hash calculations on the NSEC3 records and will not limit the work by the mitigation introduced in 1.19.1. As a side effect, a global lock for the negative cache will be held for the duration of the hashing, blocking other threads that need to consult the negative cache. Coordinated attacks could raise the vulnerability to denial of service. Unbound 1.25.1 contains a patch with a fix to bound the vulnerable code path with the existing limit for NSEC3 hash calculations.

CVSS Base Scores

version 3.1