Local privilege escalation via hard-link security-descriptor overwrite
Published Jun 29, 2020 · Updated Aug 4, 2024
Privilege escalation in Avast Free Antivirus and AVG AntiVirus Free before 20.4 allows local users to gain write access to arbitrary files. The SYSTEM-level instup.exe repair process follows a user-created hard link and replaces the linked file's security descriptor with permissions granting the Users group write access. A low-privileged local user must place the link in the AVG Browser folder and invoke Repair App; exploitation changes file permissions rather than directly executing code.
Summary
What happened
Privilege escalation in Avast Free Antivirus and AVG AntiVirus Free before 20.4 allows local users to gain write access to arbitrary files. The SYSTEM-level instup.exe repair process follows a user-created hard link and replaces the linked file's security descriptor with permissions granting the Users group write access. A low-privileged local user must place the link in the AVG Browser folder and invoke Repair App; exploitation changes file permissions rather than directly executing code.
The record
- CVE
- CVE-2020-13657
- Published
- Jun 29, 2020
- Updated
- Aug 4, 2024
- Vendor
- Unknown vendor
- Product
- Unknown product
- Classifications
- T1068
- Attack vector
- local
- Privileges
- authenticated
Timeline
How it unfolded
- Jun 29, 2020CVE publishedPublication date reported by the CVE source.
- Aug 4, 2024Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
What conditions does exploitation require?
What is affected?
Affected products and versions are unavailable in this record.
Attacks
What attackers are doing with it
Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.
Weakness, pattern, technique
Public exploit references
- Hard-link Repair App proof of conceptproof of concept · demonstrated
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Technologies
Your stack
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Your stack
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