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PatchSiren cyber security CVE debrief

CVE-2026-42248 Ollama CVE debrief

Ollama for Windows versions 0.12.10 through 0.17.5 fail to verify the integrity or authenticity of downloaded update executables. The Windows implementation of the update verification routine unconditionally returns success, bypassing digital signature and trust validation before staging or executing update payloads. Combined with silent automatic updates on Windows, this enables attacker-supplied executables to be automatically installed and executed without user awareness. The vulnerability was reported to maintainers without response regarding vulnerable version details. Testing confirmed versions 0.12.10 to 0.17.5 as vulnerable; other versions may also be affected.

Vendor
Ollama
Product
Unknown
CVSS
HIGH 7.7
CISA KEV
Not listed in stored evidence
Original CVE published
2026-04-29
Original CVE updated
2026-05-18
Advisory published
2026-04-29
Advisory updated
2026-05-18

Who should care

Organizations running Ollama on Windows endpoints, particularly those with automatic updates enabled. Security teams monitoring supply chain integrity and software update mechanisms. Developers of applications with automatic update features requiring platform-specific security implementations.

Technical summary

The vulnerability exists in Ollama's Windows update mechanism where the verification function is implemented to always return success, disabling signature validation. This architectural flaw in the update pipeline allows arbitrary executables to be accepted as legitimate updates. The silent automatic update feature on Windows compounds risk by removing user approval gates. The attack vector requires network position to intercept or redirect update requests, but successful exploitation yields high-impact code execution with the privileges of the Ollama application.

Defensive priority

HIGH

Recommended defensive actions

  • Disable automatic updates in Ollama for Windows and manually verify update sources until patched
  • Monitor for unexpected Ollama update activity or new executables in Ollama installation directories
  • Apply updates only from verified official channels after integrity verification is confirmed restored
  • Consider network segmentation to limit Ollama host exposure to potential update interception attacks
  • Review endpoint detection rules for unauthorized executable staging in Ollama update paths

Evidence notes

The CVE description and NVD record confirm the Windows-specific verification bypass and silent automatic update behavior. CERT.PL advisory provides third-party confirmation. CPE criteria specify affected versions 0.12.10 through 0.17.5.

Official resources

2026-04-29T12:16:18.917Z