Microsoft Windows TS WebProxy Directory Traversal
CVE-2015-0016 is a high-severity improper limitation of a pathname to a restricted directory vulnerability in Windows 7 from Microsoft, with a CVSS 3.1 base score of 7.8 out of 10. It can be exploited with local access to the system by an unauthenticated attacker, but only if a user takes part, for example by opening a link or file. CISA added it to the Known Exploited Vulnerabilities catalogue on May 25, 2022, which means attacks have been observed in the wild.
Attackers are already exploiting this vulnerability, according to CISA.
What to do
- Check which version of Windows 7 you run against the affected versions below, and install the vendor's latest release.
- CISA's required action: Apply updates per vendor instructions.
- Read the advisory on docs.microsoft.com for workarounds and exact fixed builds.
- Because the attack needs a user to take part, warn users about unexpected links and files related to this product until it is patched.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Microsoft | Windows 7 | Not specified in the record | Not stated |
| Microsoft | Windows 8 | Not specified in the record | Not stated |
| Microsoft | Windows 8.1 | Not specified in the record | Not stated |
| Microsoft | Windows Rt | Not specified in the record | Not stated |
| Microsoft | Windows Rt 8.1 | Not specified in the record | Not stated |
| Microsoft | Windows Server 2008 | r2 | Not stated |
| Microsoft | Windows Server 2012 | r2 | Not stated |
| Microsoft | Windows Vista | Not specified in the record | Not stated |
Version data comes from NVD's product matching. Confirm against the vendor advisory before deciding you are unaffected.
How the severity score breaks down
- Attack vector
- LocalThe attacker needs local access or must trick a user into running something.
- Attack complexity
- LowNo special conditions are needed; the attack works reliably.
- Privileges required
- NoneNo account or login is needed.
- User interaction
- RequiredA user must take an action such as opening a file or link.
- Scope
- UnchangedImpact stays within the vulnerable component.
- Confidentiality
- HighAll data handled by the component can be read.
- Integrity
- HighData or code can be modified at will.
- Availability
- HighThe component can be taken down completely.
Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H. Scored by NVD.
| Scoring system | Score | Severity | Scored by |
|---|---|---|---|
| CVSS 3.1 | 7.8 | High | NVD |
| CVSS 3.1 | 7.8 | High | CISA (ADP) |
| CVSS 2.0 | 9.3 | High | NVD |
Official description
Directory traversal vulnerability in the TS WebProxy (aka TSWbPrxy) component in Microsoft Windows Vista SP2, Windows 7 SP1, Windows Server 2008 R2 SP1, Windows 8, Windows 8.1, Windows Server 2012 Gold and R2, and Windows RT Gold and 8.1 allows remote attackers to gain privileges via a crafted pathname in an executable file, as demonstrated by a transition from Low Integrity to Medium Integrity, aka "Directory Traversal Elevation of Privilege Vulnerability."
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Improper Limitation of a Pathname to a Restricted Directory
The product uses external input to construct a pathname that is intended to identify a file or directory that is located underneath a restricted parent directory, but the product does not properly neutralize special elements within the pathname that can cause the pathname to resolve to a location that is outside of the restricted directory.
How developers prevent this class of flaw
- For any security checks that are performed on the client side, ensure that these checks are duplicated on the server side, in order to avoid CWE-602. Attackers can bypass the client-side checks by modifying values after the checks have been performed, or by changing the client to remove the client-side checks entirely. Then, these modified values would be submitted to the server.
- Use a vetted library or framework that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid.
- Use an application firewall that can detect attacks against this weakness. It can be beneficial in cases in which the code cannot be fixed (because it is controlled by a third party), as an emergency prevention measure while more comprehensive software assurance measures are applied, or to provide defense in depth.
More Improper Limitation of a Pathname to a Restricted Directory vulnerabilities (CWE-22)
Timeline
- CVE record published.
- Added to CISA's Known Exploited Vulnerabilities catalogue.
- Deadline for US federal agencies to remediate, set by CISA.
- CISA published its SSVC assessment (exploitation: active, automatable: no, technical impact: total).
- Record last changed materially (score, affected products, status or references).
References
Third-party and government advisories
- exchange.xforce.ibmcloud.com/vulnerabilities/99515Third Party Advisory, VDB Entry
- exchange.xforce.ibmcloud.com/vulnerabilities/99516Third Party Advisory, VDB Entry
- cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2015-0016US Government Resource
Technical write-ups (may include proof of concept)
- blog.trendmicro.com/trendlabs-security-intelligence/cve-2015-0016-escaping-the-internet-explorer-sandbox/Exploit
- packetstormsecurity.com/files/130201/MS15-004-Microsoft-Remote-Desktop-Services-Web-Proxy-IE-Sandbox-Escape.h…Exploit, Third Party Advisory, VDB Entry
- exploit-db.com/exploits/35983Exploit, Third Party Advisory, VDB Entry
Recent Improper Limitation of a Pathname to a Restricted Directory vulnerabilities
- 3.5 Low severity
IBM InfoSphere BigInsights Invalid Input Exploited
- 7.5 High severity
Ruby on Rails Directory Traversal Exploited
- 9.8 Critical severity
- 9.8 Critical severity
Adobe ColdFusion Directory Traversal Exploited
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