CVE Vulnerabilities

CVE-2021-28636

Uncontrolled Search Path Element

Published: Aug 20, 2021 | Modified: Aug 31, 2021
CVSS 3.x
N/A
Source:
NVD
CVSS 2.x
8.5 HIGH
AV:N/AC:M/Au:S/C:C/I:C/A:C
RedHat/V2
RedHat/V3
Ubuntu

Acrobat Reader DC versions 2021.005.20054 (and earlier), 2020.004.30005 (and earlier) and 2017.011.30197 (and earlier) are affected by an Uncontrolled Search Path Element vulnerability. An attacker with access to the victims C:/ folder could leverage this vulnerability to achieve arbitrary code execution in the context of the current user. Exploitation of this issue requires user interaction in that a victim must open a malicious file.

Weakness

The product uses a fixed or controlled search path to find resources, but one or more locations in that path can be under the control of unintended actors.

Affected Software

Name Vendor Start Version End Version
Acrobat_dc Adobe 15.008.20082 21.005.20054
Acrobat_dc Adobe 17.011.30059 17.011.30197
Acrobat_dc Adobe 20.001.30005 20.004.30005
Acrobat_reader_dc Adobe 15.008.20082 21.005.20054
Acrobat_reader_dc Adobe 17.011.30059 17.011.30197
Acrobat_reader_dc Adobe 20.001.30005 20.004.30005

Extended Description

Although this weakness can occur with any type of resource, it is frequently introduced when a product uses a directory search path to find executables or code libraries, but the path contains a directory that can be modified by an attacker, such as “/tmp” or the current working directory. In Windows-based systems, when the LoadLibrary or LoadLibraryEx function is called with a DLL name that does not contain a fully qualified path, the function follows a search order that includes two path elements that might be uncontrolled:

In some cases, the attack can be conducted remotely, such as when SMB or WebDAV network shares are used. One or more locations in that path could include the Windows drive root or its subdirectories. This often exists in Linux-based code assuming the controlled nature of the root directory (/) or its subdirectories (/etc, etc), or a code that recursively accesses the parent directory. In Windows, the drive root and some of its subdirectories have weak permissions by default, which makes them uncontrolled. In some Unix-based systems, a PATH might be created that contains an empty element, e.g. by splicing an empty variable into the PATH. This empty element can be interpreted as equivalent to the current working directory, which might be an untrusted search element. In software package management frameworks (e.g., npm, RubyGems, or PyPi), the framework may identify dependencies on third-party libraries or other packages, then consult a repository that contains the desired package. The framework may search a public repository before a private repository. This could be exploited by attackers by placing a malicious package in the public repository that has the same name as a package from the private repository. The search path might not be directly under control of the developer relying on the framework, but this search order effectively contains an untrusted element.

Potential Mitigations

References