Root privilege escalation via writable scoreboard pointers
Published Oct 25, 2021 · Updated Sep 17, 2024
Out-of-bounds writes in PHP-FPM 7.3.x through 7.3.31, 7.4.x before 7.4.25, and 8.0.x before 8.0.12 allow local users to gain root privileges. PHP-FPM stores worker-scoreboard pointers in shared memory writable by child processes, then the root master dereferences those attacker-controlled pointers during worker allocation and cleanup. Exploitation requires PHP code execution and a worker-memory read/write primitive in a deployment whose master runs as root and workers run with lower privileges.
Summary
What happened
Out-of-bounds writes in PHP-FPM 7.3.x through 7.3.31, 7.4.x before 7.4.25, and 8.0.x before 8.0.12 allow local users to gain root privileges. PHP-FPM stores worker-scoreboard pointers in shared memory writable by child processes, then the root master dereferences those attacker-controlled pointers during worker allocation and cleanup. Exploitation requires PHP code execution and a worker-memory read/write primitive in a deployment whose master runs as root and workers run with lower privileges.
The record
- CVE
- CVE-2021-21703
- Published
- Oct 25, 2021
- Updated
- Sep 17, 2024
- Vendor
- The PHP Group
- Product
- PHP
- Classifications
- CWE-284, CWE-787, T1068
- Attack vector
- local
- Privileges
- authenticated
Timeline
How it unfolded
- Oct 25, 2021CVE publishedPublication date reported by the CVE source.
- Sep 17, 2024Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
Compare your product and version with the public record. A matching version still requires validation against your environment.
Is a vulnerable build present?
Compare these published version ranges with your installed build and any vendor patches.
- Affected versionversion=7.3.x <=7.3.31
- Affected versionversion=7.4.x <7.4.25
- Affected versionversion=8.0.X <8.0.12
What conditions does exploitation require?
What is affected?
Published CVSS scores
CVSS describes severity. EPSS estimates exploitation probability.
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
- PHP-FPM local-root technical demonstrationproof of concept · demonstrated
Labels summarize the accepted research assessment. They do not indicate a test against your environment.
Technologies
Your stack
See the directory against your own environment.
Your stack
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