Heap-based Buffer Overflow Affecting python2-unbound package, versions <0:1.7.3-15.amzn2.0.17


Severity

Recommended
0.0
high
0
10

Based on Amazon Linux security rating.

Threat Intelligence

EPSS
0.48% (39th percentile)

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  • Snyk IDSNYK-AMZN2-PYTHON2UNBOUND-20244752
  • published29 Sept 2026
  • disclosed16 Sept 2026

Introduced: 16 Sep 2026

CVE-2026-81634  (opens in a new tab)
CWE-122  (opens in a new tab)

How to fix?

Upgrade Amazon-Linux:2 python2-unbound to version 0:1.7.3-15.amzn2.0.17 or higher.
This issue was patched in ALAS2-2026-3941.

NVD Description

Note: Versions mentioned in the description apply only to the upstream python2-unbound package and not the python2-unbound package as distributed by Amazon-Linux. See How to fix? for Amazon-Linux:2 relevant fixed versions and status.

In NLnet Labs Unbound up to and including 1.26.0, a 255 length query name with a large TCP response can lead to a heap buffer overflow during the RRSet canonicalisation routine. This is caused by missing to add the first owner name into the buffer length check. A malicious actor operating a malicious name server or tampering with an incoming response to Unbound (canonicalisation happens before DNSSEC validation), can trigger the vulnerability.

CVSS Base Scores

version 3.1