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HighVulnerabilityupdated 27 Oct 2026, 12:23 UTC

Squid proxy has several flaws that let attackers crash it or leak data

Squid is a widely used internet proxy server. Attackers on the network can exploit these flaws to make it stop working or to see information it should keep private.

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 the Squid proxy server allow a remote, unauthenticated attacker to cause a denial of service or disclose information. A second advisory notes further information-disclosure flaws and an unspecified attack.

Why it is dangerous: A crashed or leaking proxy disrupts internet access for everyone behind it and can expose internal traffic or data. Organisations running Squid as a gateway are most at risk.

Are you affected?

You are affected if you run Squid as a proxy or caching server exposed to untrusted clients or networks.

Squid (versions not specified in the source material)

What to do

  1. Check your Squid version against the vendor's security advisory and update to the fixed release as soon as one is available.
  2. Restrict which clients can reach the Squid port with firewall rules or access control lists.
  3. Monitor Squid logs and service availability for crashes or unusual traffic.

Timeline

  1. 27 Oct 2026, 12:16 UTC
    Publicly disclosed
  2. 27 Oct 2026, 12:16 UTC
    Reported by CERT-Bund (BSI) · CERT-Bund (BSI)
  3. 27 Oct 2026, 12:17 UTC
    Reported by CERT-Bund (BSI) · CERT-Bund (BSI)
  4. 27 Oct 2026, 12:18 UTC
    Picked up by Zero Radar

Sources 2 reports, oldest first

Official vendor, government CERT or advisory database

Technical details

ID
ZR-bccdd6c1
Disclosed
27 Oct 2026, 12:16 UTC
On Zero Radar
27 Oct 2026, 12:18 UTC (2 min after disclosure)
Last change
27 Oct 2026, 12:23 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

Squid proxy has several flaws that let attackers crash it or leak data · Zero Radar