CVE-2020-9839

HIGH

macOS cfprefsd Arbitrary File Write Local Privilege Escalation

Title source: metasploit
STIX 2.1

Exploitation Summary

EIP tracks 1 public exploit for CVE-2020-9839. Includes Metasploit module exploits/osx/local/cfprefsd_race_condition.

AI-analyzed exploit summary This Metasploit module exploits a race condition in cfprefsd (CVE-2020-9839) to overwrite /etc/pam.d/login, allowing passwordless root login via the `login root` command. It includes payload delivery and cleanup mechanisms.

Description

A race condition was addressed with improved state handling. This issue is fixed in iOS 13.5 and iPadOS 13.5, macOS Catalina 10.15.5, tvOS 13.4.5, watchOS 6.2.5. An application may be able to gain elevated privileges.

Exploits (1)

metasploit WORKING POC EXCELLENT
rubypocosx
https://github.com/rapid7/metasploit-framework/blob/master/modules/exploits/osx/local/cfprefsd_race_condition.rb

This Metasploit module exploits a race condition in cfprefsd (CVE-2020-9839) to overwrite /etc/pam.d/login, allowing passwordless root login via the `login root` command. It includes payload delivery and cleanup mechanisms.

Classification
Working Poc 100%
Attack Type
Lpe
Complexity
Moderate
Reliability
Racy
Target: macOS <= 10.15.4
No auth needed
Prerequisites: Unsandboxed process access · Write permissions in a temporary directory
devstral-2 · analyzed Feb 16, 2026 Full analysis →

References (4)

Core 4
Core References
Vendor Advisory x_refsource_misc
https://support.apple.com/HT211168
Vendor Advisory x_refsource_misc
https://support.apple.com/HT211170
Vendor Advisory x_refsource_misc
https://support.apple.com/HT211171
Vendor Advisory x_refsource_misc
https://support.apple.com/HT211175

Scores

CVSS v3 7.0
EPSS 0.0367
EPSS Percentile 88.2%
Attack Vector LOCAL
CVSS:3.1/AV:L/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H

Details

CWE
CWE-362
Status published
Products (5)
apple/ipados < 13.5
apple/iphone_os < 13.5
apple/mac_os_x < 10.15.5
apple/tvos < 13.4.5
apple/watchos < 6.2.5
Published Jun 09, 2020
Tracked Since Feb 18, 2026