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HighVulnerabilityupdated 26 Oct 2026, 12:39 UTC

libxml2: flaw lets remote attackers crash services (denial of service)

A widely used XML parsing library has a bug that lets an attacker make programs that use it stop working. The attacker does not get into your data, but your service can go down.

Official source
SeverityHighVulnerability
Being exploited?UnclearNo reports either way yet
Fix available?UnclearNo fixed version published in the sources yet
How sure is this?Official sourceBacked by an official source

What happened

Multiple vulnerabilities in libxml2 allow a remote attacker to trigger a denial-of-service condition. The advisories rate severity as high for an authenticated attacker and medium/low for an anonymous attacker.

Why it is dangerous: Websites, APIs, and tools that parse XML and use libxml2 can be knocked offline, disrupting availability. Services exposed to the internet are most at risk.

Are you affected?

You are affected if you run software that uses libxml2 to parse XML, especially internet-facing web services or APIs.

What to do

  1. Check which of your applications or servers use libxml2, including via PHP, Python, or other packages.
  2. Install the vendor updates for libxml2 and the software built on it as soon as they are available.
  3. Monitor services for unusual crashes or restarts until patched.

Timeline

  1. 26 Oct 2026, 11:45 UTC
    Publicly disclosed
  2. 26 Oct 2026, 11:45 UTC
    Reported by CERT-Bund (BSI) · CERT-Bund (BSI)
  3. 26 Oct 2026, 11:59 UTC
    Picked up by Zero Radar
  4. 26 Oct 2026, 12:31 UTC
    Reported by CERT-Bund (BSI) · CERT-Bund (BSI)
  5. 26 Oct 2026, 12:31 UTC
    Reported by CERT-Bund (BSI) · CERT-Bund (BSI)

Sources 3 reports, oldest first

Official vendor, government CERT or advisory database

Technical details

ID
ZR-bff5d0ce
Disclosed
26 Oct 2026, 11:45 UTC
On Zero Radar
26 Oct 2026, 11:59 UTC (14 min after disclosure)
Last change
26 Oct 2026, 12:39 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

libxml2: flaw lets remote attackers crash services (denial of service) · Zero Radar