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HighVulnerabilityCVE-2026-114605updated 27 Oct 2026, 15:37 UTC

dnspython can burn excessive CPU on malicious DNS messages

A specially crafted DNS message can make a Python program using this library work very hard, slowing it down or making it stop responding. Only programs that parse DNS messages from untrusted sources are at risk.

Fixed in dnspython 2.9.0Official, 2 sources
SeverityHighCVSS 7.5 of 10
Being exploited?UnclearNo reports either way yet
Fix available?Yesdnspython 2.9.0 · since 27 Oct 2026
How sure is this?Official, 2 sourcesBacked by an official source

How the attack works simplified

  1. 1Attacker sends messageCrafted DNS message with pointer chains
  2. 2Message reaches appApp parses untrusted DNS wire data
  3. 3Name decompression loopsNo hop limit on compression pointers
  4. 4CPU exhaustedApplication slows down or stops
  5. ResultApplication degraded or denied service

What happened

dns.name.from_wire_parser() follows DNS name compression pointer chains without a hop limit, so a crafted wire-format message forces excessive pointer traversal during name decompression, causing high CPU use or denial of service.

Why it is dangerous: Applications that process untrusted DNS wire-format messages can be degraded or taken offline, since the extra CPU work is triggered by attacker-supplied input.

Are you affected?

You are affected if you use the pip package dnspython older than 2.9.0 in an application that parses DNS wire-format messages from untrusted sources.

Package / productAffected versionsFixed in
dnspython · pip< 2.9.02.9.0

What to do

  1. Upgrade dnspython to version 2.9.0 or later
  2. Check whether your applications parse untrusted DNS wire-format messages
  3. Monitor CPU usage of DNS-handling services until the upgrade is deployed

Timeline

  1. 22 Oct 2026, 17:16 UTC
    Publicly disclosed
  2. 22 Oct 2026, 17:16 UTC
    Reported by NVD · NVD
  3. 27 Oct 2026, 15:37 UTC
    GitHub Advisory reported on it · GitHub Advisory
  4. 27 Oct 2026, 15:37 UTC
    Fixed version published: dnspython 2.9.0 · GitHub Advisory

Sources 2 reports, oldest first

Official vendor, government CERT or advisory database

Technical details

ID
CVE-2026-114605 · GHSA-45c3-73f7-pv4m
CVSS
7.5 / 10
EPSS
0.5% chance of exploitation within 30 days
Disclosed
22 Oct 2026, 17:16 UTC
On Zero Radar
before the radar started
Last change
27 Oct 2026, 15:37 UTC

The plain-language parts and the attack diagram were written by an AI model (anthropic/claude-haiku-5.5) from the sources above. Facts like versions, exploitation and dates come from the sources themselves. How Zero Radar works

dnspython can burn excessive CPU on malicious DNS messages · Zero Radar