Quick answer
Direct answer
Risk scores
| CVSS metric | What it means |
|---|---|
| Attack vector (AV:N) | Network: reachable remotely |
| Attack complexity (AC:L) | Low complexity |
| Attack requirements (AT:N) | No attack requirements |
| Privileges required (PR:N) | No privileges required |
| User interaction (UI:N) | No user interaction |
| Confidentiality (VC:H) | High confidentiality impact |
| Integrity (VI:H) | High integrity impact |
| Availability (VA:H) | High availability impact |
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
About Altium On-Prem Enterprise Server
CVE-2026-11420 affects Altium On-Prem Enterprise Server, a product from Altium. Before acting, confirm where Altium On-Prem Enterprise Server runs in your estate, who owns it and whether it is reachable from the internet, because exposure decides real risk more than the score alone.
What the flaw is
In plain terms: Two path traversal vulnerabilities in the Network Installation Service (NIS) of Altium Enterprise Server allow an unauthenticated network attacker to write arbitrary files to any writable location on the server filesystem and to read package archive files from the server. No authentication, session, or credentials are required. Because content-controlled files can be written to web-accessible directories, or used to overwrite application binaries or configuration files, exploitation can be escalated to remote code execution in the context of the service account, and can disclose deployment package contents. Altium 365 cloud deployments are not affected, as the Network Installation Service is not part of the cloud offering.
The weakness class is Path Traversal. An attacker can reach files outside the intended folder by tampering with a file path.
Based on its CVSS vector, the flaw can be reached over the network, needs no login, and needs no user interaction. Apply the vendor fix and confirm exposure on internet facing and business critical assets first.
Affected versions and timeline
| Field | Detail |
|---|---|
| Product | Altium On-Prem Enterprise Server |
| Affected versions | On-Prem Enterprise Server before 8.1.1 |
| Published | Jun 5, 2026 |
| Last modified | Jul 23, 2026 |
| Added to CISA KEV | Not listed |
| Assigning CNA | 4760f414-e1ae-4ff1-bdad-c7a9c3538b79 |
How to detect it
- Inventory every instance of Altium On-Prem Enterprise Server and record the running version against the affected range above.
- Check external attack surface scans for internet facing instances of the component.
- Review logs on affected systems for unusual requests, errors or new processes around the vulnerable function.
- Confirm with an authenticated vulnerability scan once your scanner has a check for this CVE.
How to fix it
- Apply the fixed version of Altium On-Prem Enterprise Server named in the vendor advisory.
- If patching must wait, restrict network access to the affected service and put it behind authentication or a web application firewall rule.
- Rescan after the change to prove the exposure is gone, then close the ticket.
CTEM action plan
| CTEM stage | What to do for this CVE |
|---|---|
| Scope | Add every business service that depends on Altium On-Prem Enterprise Server to the current CTEM cycle. |
| Discover | Find all instances, including shadow and cloud deployments, and record versions and exposure. |
| Prioritize | Rank using EPSS and CVSS together with asset exposure and business impact. |
| Validate | Confirm the flaw is reachable and exploitable in your environment and that compensating controls work. |
| Mobilize | Assign the fix to the asset owner with a due date matched to the priority, then verify closure. |
CWE References
- CWE-22: Path Traversal More CVEs with this weakness
- CWE-306: Missing Authentication More CVEs with this weakness
Technical References
Frequently asked questions
Related CVEs
A path traversal vulnerability exists in the Altium Enterprise Server Vault Service UploadController due to improper validation of a user-controlled path component in image upload requests. An authenticated user can supply a crafted absolute path so that the configured storage root is discarded, allowing arbitrary files to be written to any location on the server filesystem writable by the service account. Because content-controlled files can be written to web-accessible directories, or used to overwrite application binaries or configuration files, this can be escalated to remote code execution, service takeover, or denial of service. Altium 365 cloud deployments are not affected, as the affected endpoint is not reachable and the cloud storage architecture mitigates the file-write primitive.
A hard-coded cryptographic key is used by Altium Enterprise Server to sign file download URLs in the Vault service. Because the key is identical across all installations, an unauthenticated network attacker who can reach the server can forge valid download signatures and retrieve files from the Vault storage area without any authentication, session, or credentials. A separate path traversal vulnerability in the same download endpoint allows the configured storage root to be escaped, enabling reads of arbitrary files on the server filesystem. Combined, these issues allow an unauthenticated attacker to obtain sensitive server configuration and key material, which can lead to full server compromise. The vulnerability can be chained with CVE-2026-9152 to enumerate and bulk-download stored content. Altium 365 cloud deployments are not impacted in practice, as file storage uses object storage rather than the local filesystem.
AES contains a SQL injection vulnerability due to an inactive configuration that prevents the latest SQL parsing logic from being applied. When this configuration is not enabled, crafted input may be improperly handled, allowing attackers to inject and execute arbitrary SQL queries.
Mesop is a Python-based UI framework that allows users to build web applications. Versions 1.2.2 and below contain a Path Traversal vulnerability that allows any user supplying an untrusted state_token through the UI stream payload to arbitrarily target files on the disk under the standard file-based runtime backend. This can result in application denial of service (via crash loops when reading non-msgpack target files as configurations), or arbitrary file manipulation. This vulnerability heavily exposes systems hosted utilizing FileStateSessionBackend. Unauthorized malicious actors could interact with arbitrary payloads overwriting or explicitly removing underlying service resources natively outside the application bounds. This issue has been fixed in version 1.2.3.
Vociferous provides cross-platform, offline speech-to-text with local AI refinement. Prior to 4.4.2, the vulnerability exists in src/api/system.py within the export_file route. The application accepts a JSON payload containing a filename and content. While the developer intended for a native UI dialog to handle the file path, the API does not validate the filename string before it is processed by the backends filesystem logic. Because the API is unauthenticated and the CORS configuration in app.py is overly permissive (allow_origins=["*"] or allowing localhost), an external attacker can bypass the UI entirely. By using directory traversal sequences (../), an attacker can force the app to write arbitrary data to any location accessible by the current user's permissions. This vulnerability is fixed in 4.4.2.
Erugo is a self-hosted file-sharing platform. In versions up to and including 0.2.14, an authenticated low-privileged user can upload arbitrary files to any specified location due to insufficient validation of user‑supplied paths when creating shares. By specifying a writable path within the public web root, an attacker can upload and execute arbitrary code on the server, resulting in remote code execution (RCE). This vulnerability allows a low-privileged user to fully compromise the affected Erugo instance. Version 0.2.15 fixes the issue.
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