Kernel privilege escalation via unlocked voucher accounting
Published Apr 2, 2021 · Updated Oct 21, 2025
Improper locking in Apple's XNU kernel allows local users to elevate privileges on iOS and iPadOS before 14.4 and affected macOS releases. In user_data_get_value(), an unlocked non-atomic increment desynchronizes Mach voucher counters, enabling a second race to reuse a freed user_data_element_t. A malicious application must run locally and win both races; successful exploitation reaches kernel privileges, while the public iOS 14 proof of concept crashes the kernel.
Summary
What happened
Improper locking in Apple's XNU kernel allows local users to elevate privileges on iOS and iPadOS before 14.4 and affected macOS releases. In user_data_get_value(), an unlocked non-atomic increment desynchronizes Mach voucher counters, enabling a second race to reuse a freed user_data_element_t. A malicious application must run locally and win both races; successful exploitation reaches kernel privileges, while the public iOS 14 proof of concept crashes the kernel.
The record
- CVE
- CVE-2021-1782
- Published
- Apr 2, 2021
- Updated
- Oct 21, 2025
- Vendor
- Apple
- Product
- iOS and iPadOS
- Classifications
- CWE-667, CAPEC-26, T1068
- Attack vector
- local
- Privileges
- authenticated
Timeline
How it unfolded
- Apr 2, 2021CVE publishedPublication date reported by the CVE source.
- Oct 21, 2025Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
Compare these published version ranges with your installed build and any vendor patches.
- Affected versionversion=unspecified <14.4
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
- cicuta_virosafunctional · demonstrated
- Synacktiv voucher_leak proof of conceptproof of concept · demonstrated
Labels summarize the accepted research assessment. They do not indicate a test against your environment.
Reported exploitation
- Apple report of active exploitationreported exploitation
- CISA Known Exploited Vulnerabilities entryknown exploited catalog
Technologies
Your stack
See the directory against your own environment.
Your stack
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