CVE-2019-18276: gnu bash Improper Check for Dropped Privileges

Vulnerability summary

CVE-2019-18276 is a high (CVSS 7.8) Improper Check for Dropped Privileges vulnerability in gnu bash. EPSS estimates a 2.61% chance of exploitation in the next 30 days, higher than 85.1% of scored vulnerabilities. 2 public exploits are recorded.

Timeline

1. 28-11-2019
   PublishedVulnerability first disclosed.
2. 14-10-2026
   Last modifiedVulnerability information updated.

Description

An issue was discovered in disable_priv_mode in shell.c in GNU Bash through 5.0 patch 11. By default, if Bash is run with its effective UID not equal to its real UID, it will drop privileges by setting its effective UID to its real UID. However, it does so incorrectly. On Linux and other systems that support "saved UID" functionality, the saved UID is not dropped. An attacker with command execution in the shell can use "enable -f" for runtime loading of a new builtin, which can be a shared object that calls setuid() and therefore regains privileges. However, binaries running with an effective UID of 0 are unaffected.

• CWE-273Improper Check for Dropped PrivilegesThe product attempts to drop privileges but does not check or incorrectly checks to see if the drop succeeded.