CVE-2026-42249
Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.
NVD · uneditedOllama 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.
Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.
dbcve analysis · high confidenceOllama for Windows has a critical path traversal vulnerability in its update mechanism where attacker-controlled HTTP response headers are used to construct file paths without validation. Attackers can use '../' sequences to write arbitrary executables to sensitive locations like the Windows Startup directory. When combined with missing signature verification (CVE-2026-42248), this enables automatic persistent code execution through silent automatic updates.
Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.
Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.
NVD · CPE data>= 0.12.10, <= 0.17.5CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.
From the vector- Attack vector
- Network
- Complexity
- Low
- Privileges
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- High
- Integrity
- High
- Availability
- High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.
dbcve checksWork through these to decide whether this CVE applies to you.
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Confirm Ollama installation on WindowsCheck for Ollama installation by looking for the executable in common locations: %LOCALAPPDATA%\Ollama, %ProgramFiles%\Ollama, or run 'ollama --version' in Command Prompt/PowerShellAffected if Ollama is installed on the system
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Determine installed Ollama versionRun 'ollama --version' or check the version through the Ollama GUI/window. Compare the version number to the affected range >= 0.12.10 and <= 0.17.5Affected if The installed version falls within 0.12.10 through 0.17.5 inclusive
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Verify if automatic updates are enabledCheck Ollama configuration files in the app data directory (%APPDATA%\Ollama or %LOCALAPPDATA%\Ollama) for update-related settings, or check the Ollama UI for update notification preferencesAffected if Automatic update checks or downloads are enabled in Ollama settings
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Inspect update staging directory for unexpected filesLocate the temporary staging directory used by Ollama's update mechanism (check %LOCALAPPDATA%\Temp\Ollama or similar temp locations) and examine its contents for any unexpected .exe or .dll filesAffected if Files exist outside the expected staging directory structure, or unexpected executables are present in temp folders related to Ollama
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Examine Windows Startup folder for suspicious entriesCheck %APPDATA%\Microsoft\Windows\Start Menu\Programs\Startup and %PROGRAMDATA%\Microsoft\Windows\Start Menu\Programs\Startup for any Ollama-related executables that were not intentionally installedAffected if Unexpected Ollama executables or scripts appear in Windows Startup folders that were not manually configured by the user
A user is affected if Ollama version 0.12.10 through 0.17.5 is installed with automatic updates enabled on Windows, particularly if unexpected executables appear in the Startup folder or outside the update staging directory.
Generated from the published advisory. Verify against your own configuration.
Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.
dbcve · scopedImplement strict validation of all HTTP header-derived values before use in file path construction, implement cryptographic signature verification for all update payloads, and consider disabling automatic updates until comprehensive security fixes are deployed.
Latest version available at ollama.com (version > 0.17.5)
- 1. Identify the current Ollama version installed by running `ollama --version` or checking the application
- 2. Since the vendor has not published a fix in the advisory period, upgrade to the latest available version from the official Ollama repository (ollama.com) or GitHub releases
- 3. After upgrading, verify the new version is running: `ollama --version`
- 4. For Windows systems where automatic updates may have already staged malicious files, perform a full antivirus scan of the system, especially the Startup directory (%APPDATA%\Microsoft\Windows\Start Menu\Programs\Startup) and Ollama's update staging directory
- 5. Review the Ollama update cache directories for any unexpected files and remove them
- 6. Monitor for any suspicious new executables or processes originating from Ollama's installation directory
Generated from the published advisory — verify against the referenced sources before acting.
- Consultation10.0 h
- Implementation24.0 h
- Testing16.0 h
- Review / QA10.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2026-42249 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2026-42249 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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- Version or environment caveats, and links to real fixes
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