CVE-2024-39698

electron-updater allows for automatic updates for Electron apps. The file packages/electron-updater/src/windowsExecutableCodeSignatureVerifier.ts implements the signature validation routine for Electron applications on Windows. Because of the surrounding shell, a first pass by cmd.exe expands any environment variable found in command-line above. This creates a situation where verifySignature() can be tricked into validating the certificate of a different file than the one that was just downloaded. If the step is successful, the malicious update will be executed even if its signature is invalid. This attack assumes a compromised update manifest (server compromise, Man-in-the-Middle attack if fetched over HTTP, Cross-Site Scripting to point the application to a malicious updater server, etc.). The patch is available starting from 6.3.0-alpha.6.

Weakness

The product receives input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could be interpreted as variable name delimiters when they are sent to a downstream component.

Affected Software

Potential Mitigations

• Assume all input is malicious. Use an “accept known good” input validation strategy, i.e., use a list of acceptable inputs that strictly conform to specifications. Reject any input that does not strictly conform to specifications, or transform it into something that does.
• When performing input validation, consider all potentially relevant properties, including length, type of input, the full range of acceptable values, missing or extra inputs, syntax, consistency across related fields, and conformance to business rules. As an example of business rule logic, “boat” may be syntactically valid because it only contains alphanumeric characters, but it is not valid if the input is only expected to contain colors such as “red” or “blue.”
• Do not rely exclusively on looking for malicious or malformed inputs. This is likely to miss at least one undesirable input, especially if the code’s environment changes. This can give attackers enough room to bypass the intended validation. However, denylists can be useful for detecting potential attacks or determining which inputs are so malformed that they should be rejected outright.

Related Attack Patterns

• https://cwe.mitre.org/data/definitions/15.html

References

• https://github.com/electron-userland/electron-builder/blob/140e2f0eb0df79c2a46e35024e96d0563355fc89/packages/electron-updater/src/windowsExecutableCodeSignatureVerifier.ts#L35-L41
• https://github.com/electron-userland/electron-builder/commit/ac2e6a25aa491c1ef5167a552c19fc2085cd427f
• https://github.com/electron-userland/electron-builder/pull/8295
• https://github.com/electron-userland/electron-builder/security/advisories/GHSA-9jxc-qjr9-vjxq
• https://github.com/electron-userland/electron-builder/blob/140e2f0eb0df79c2a46e35024e96d0563355fc89/packages/electron-updater/src/windowsExecutableCodeSignatureVerifier.ts#L35-L41
• https://github.com/electron-userland/electron-builder/commit/ac2e6a25aa491c1ef5167a552c19fc2085cd427f
• https://github.com/electron-userland/electron-builder/pull/8295
• https://github.com/electron-userland/electron-builder/security/advisories/GHSA-9jxc-qjr9-vjxq