Zero Radar
← feed
HighVulnerabilityupdated 27 Oct 2026, 11:37 UTC

expat XML library flaw lets remote attackers crash software

expat is a widely used library that reads XML data inside many programs. A flaw in it can let an anonymous attacker send malicious XML and make the program crash or stop responding.

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

A vulnerability in the expat XML parser library allows a remote, unauthenticated attacker to trigger memory corruption and a denial-of-service condition.

Why it is dangerous: A crashed or hung service becomes unavailable to users, and any application that parses untrusted XML using expat may be affected.

Are you affected?

You are affected if you run software that uses an expat library version covered by the CERT-Bund advisories and processes XML from untrusted sources.

expat (affected versions not specified in the provided material)

What to do

  1. Check which applications on your systems use expat and find their versions
  2. Update expat to the latest version from your vendor or distribution
  3. Restrict or monitor XML input from untrusted sources until patched

Timeline

  1. 23 Oct 2026, 10:22 UTC
    Publicly disclosed
  2. 23 Oct 2026, 10:22 UTC
    Reported by CERT-Bund (BSI) · CERT-Bund (BSI)
  3. 23 Oct 2026, 10:30 UTC
    Reported by CERT-Bund (BSI) · CERT-Bund (BSI)
  4. 25 Oct 2026, 15:20 UTC
    Picked up by Zero Radar
  5. 26 Oct 2026, 11:44 UTC
    Reported by CERT-Bund (BSI) · CERT-Bund (BSI)
  6. 26 Oct 2026, 11:44 UTC
    Reported by CERT-Bund (BSI) · CERT-Bund (BSI)
  7. 26 Oct 2026, 11:45 UTC
    Reported by CERT-Bund (BSI) · CERT-Bund (BSI)
  8. 27 Oct 2026, 11:33 UTC
    Reported by CERT-Bund (BSI) · CERT-Bund (BSI)
  9. 27 Oct 2026, 11:37 UTC
    Severity raised to high

Sources 6 reports, oldest first

Official vendor, government CERT or advisory database

Technical details

ID
ZR-b7254f14 · ZR-69376fe4 · ZR-9b410135 · ZR-c196e3b6 · ZR-33f1fbcf · ZR-2ee43797
Disclosed
23 Oct 2026, 10:22 UTC
On Zero Radar
25 Oct 2026, 15:20 UTC (2 days after disclosure)
Last change
27 Oct 2026, 11:37 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

expat XML library flaw lets remote attackers crash software · Zero Radar