CVE-2026-42249
Published: 29 April 2026
Summary
CVE-2026-42249 is a critical-severity Path Traversal (CWE-22) vulnerability in Ollama Ollama. Its CVSS base score is 9.8 (Critical).
Operationally, exploitation aligns with the MITRE ATT&CK technique Exploitation for Client Execution (T1203); ranked at the 40.6th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.
Threat & Defense at a Glance
Threat & Defense Details
Likely Mitigating ControlsAI
Per-CVE control mapping for this CVE has not run yet; the list below is derived from the weakness types (CWEs) cited in the NVD entry.
Policies can require integrity verification of software prior to installation, reducing risks from unverified downloads.
Blocks installation of components lacking a valid signature, mitigating download or installation of code without integrity checks.
Acquisition and maintenance portions of the strategy drive requirements for integrity verification of downloaded or supplied code.
Mandating integrity control and approved-only changes during development prevents incorporation of code or components lacking integrity validation.
Supply chain protection requires integrity verification of acquired components, directly reducing insertion or tampering of malicious code during delivery.
Reduces exposure to code obtained without integrity verification by requiring assurance processes that confirm authenticity and absence of tampering.
Tamper resistance and detection commonly include integrity verification of code and firmware obtained from external sources.
Component authenticity requires verifying origin/integrity of acquired firmware or software, directly preventing inclusion of code without integrity checks.
MITRE ATT&CK Enterprise TechniquesAI
Why these techniques?
Path traversal in update download enables arbitrary file write to Startup folder for auto-execution (T1547.001); client-side flaw directly supports exploitation for client execution (T1203).
NVD 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…
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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.
Deeper analysisAI
Automated synthesis unavailable for this CVE.
Details
- CWE(s)