CVE-2026-42249: ollama Path Traversal

Vulnerability summary

CVE-2026-42249 is a critical (CVSS 9.8) Path Traversal vulnerability in ollama. EPSS estimates a 0.99% chance of exploitation in the next 30 days, higher than 62% of scored vulnerabilities. 1 public exploit is recorded.

Timeline

1. 29-04-2026
   PublishedVulnerability first disclosed.
2. 29-04-2026
   Last modifiedVulnerability information updated.

Description

Ollama for Windows contains a Remote Code Execution vulnerability in its update mechanism due to improper handling of attacker‑controlled HTTP response headers. When downloading updates, the application constructs local file paths using values derived from HTTP headers without validation. These values are passed directly to filepath.Join, allowing path traversal sequences (../) to be resolved and enabling files to be written outside the intended update staging directory. An attacker who can influence update responses can exploit this flaw to write arbitrary executables to attacker‑chosen locations accessible to the current user, including the Windows Startup directory. This allows execution of arbitrary executables. Critically, when chained with CVE‑2026‑42248 (Missing Signature Verification for Updates), an attacker can deliver malicious payloads that are written to sensitive locations and executed automatically. Because Ollama for Windows performs silent automatic updates and executes staged binaries without user interaction, this results in automatic and persistent code execution without user awareness. Maintainers of this project were notified early about this vulnerability, but didn't respond with the details of vulnerability or vulnerable version range. Versions from 0.12.10 to 0.17.5 were tested and confirmed as vulnerable, other versions were not tested but might also be vulnerable.

• CWE-22Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')The product uses external input to construct a pathname that is intended to identify a file or directory that is located underneath a restricted parent directory, but the product does not properly neutralize special elements within the pathname that can cause the pathname to resolve to a location that is outside of the restricted directory.
• CWE-494Download of Code Without Integrity CheckThe product downloads source code or an executable from a remote location and executes the code without sufficiently verifying the origin and integrity of the code.