CVE-2017-8823 : Security Advisory and Response
Learn about CVE-2017-8823, a use-after-free vulnerability in Tor versions before 0.2.5.16, 0.2.6 through 0.2.8.17, 0.2.9.14, 0.3.0.13, and 0.3.1.9, allowing potential code execution or DoS attacks. Find mitigation steps and long-term security practices.
Tor before 0.2.5.16, 0.2.6 through 0.2.8 before 0.2.8.17, 0.2.9 before 0.2.9.14, 0.3.0 before 0.3.0.13, and 0.3.1 before 0.3.1.9 is affected by a use-after-free vulnerability in the onion service v2 during intro-point expiration.
Understanding CVE-2017-8823
This CVE involves a use-after-free vulnerability in Tor versions before specific releases, leading to potential security risks.
What is CVE-2017-8823?
The use-after-free vulnerability in Tor versions before 0.2.5.16, 0.2.6 through 0.2.8 before 0.2.8.17, 0.2.9 before 0.2.9.14, 0.3.0 before 0.3.0.13, and 0.3.1 before 0.3.1.9 can be observed in the onion service v2 when intro-point expiration occurs. This vulnerability occurs due to mismanagement of the expiring list in specific error scenarios, also known as TROVE-2017-013.
The Impact of CVE-2017-8823
The vulnerability can be exploited by attackers to potentially execute arbitrary code or cause a denial of service (DoS) condition on the affected system.
Technical Details of CVE-2017-8823
This section provides more in-depth technical insights into the CVE.
Vulnerability Description
The use-after-free vulnerability in Tor versions before specific releases allows attackers to exploit the onion service v2 during intro-point expiration due to mismanagement of the expiring list in certain error scenarios.
Affected Systems and Versions
- Tor before 0.2.5.16
- Tor 0.2.6 through 0.2.8 before 0.2.8.17
- Tor 0.2.9 before 0.2.9.14
- Tor 0.3.0 before 0.3.0.13
- Tor 0.3.1 before 0.3.1.9
Exploitation Mechanism
The vulnerability arises from the mismanagement of the expiring list in specific error scenarios, allowing attackers to trigger the use-after-free condition and potentially execute malicious code.
Mitigation and Prevention
Protecting systems from CVE-2017-8823 requires immediate actions and long-term security practices.
Immediate Steps to Take
- Update Tor to versions 0.2.5.16, 0.2.8.17, 0.2.9.14, 0.3.0.13, or 0.3.1.9 to mitigate the vulnerability.
- Monitor network traffic for any suspicious activities that could indicate exploitation.
Long-Term Security Practices
- Regularly update and patch Tor to the latest secure versions.
- Implement network segmentation and access controls to limit the impact of potential attacks.
Patching and Updates
- Stay informed about security advisories and patches released by Tor Project to address vulnerabilities like CVE-2017-8823.