Guest privilege escalation via retained file capabilities
Published Mar 9, 2021 · Updated Aug 3, 2024
Improper permission preservation in QEMU virtiofsd before 5.2.50 allows local users to gain privileges within a guest. When xattrmap renames security.capability, virtiofsd relies on the host kernel to clear the unmapped attribute and leaves the remapped capability attached after writes. Exploitation requires xattr and xattrmap to rename security.capability plus write access to a capability-bearing executable, enabling altered code to run with its retained guest privileges.
Summary
What happened
Improper permission preservation in QEMU virtiofsd before 5.2.50 allows local users to gain privileges within a guest. When xattrmap renames security.capability, virtiofsd relies on the host kernel to clear the unmapped attribute and leaves the remapped capability attached after writes. Exploitation requires xattr and xattrmap to rename security.capability plus write access to a capability-bearing executable, enabling altered code to run with its retained guest privileges.
The record
- CVE
- CVE-2021-20263
- Published
- Mar 9, 2021
- Updated
- Aug 3, 2024
- Vendor
- QEMU Project
- Product
- QEMU
- Classifications
- CWE-281, T1548
- Attack vector
- local
- Privileges
- authenticated
Timeline
How it unfolded
- Mar 9, 2021CVE publishedPublication date reported by the CVE source.
- Aug 3, 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?
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- Affected versionversion=qemu 5.2.50
What conditions does exploitation require?
What is affected?
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
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Technologies
Your stack
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Your stack
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