Improper Check for Dropped Privileges

Affecting bash package, versions *

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Overview

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.

References

CVSS Score

7.8
low severity
  • Attack Vector
    Local
  • Attack Complexity
    Low
  • Privileges Required
    Low
  • User Interaction
    None
  • Scope
    Unchanged
  • Confidentiality
    High
  • Integrity
    High
  • Availability
    High
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H/E:F
CVE
CVE-2019-18276
CWE
CWE-273
Snyk ID
SNYK-DEBIAN9-BASH-536274
Disclosed
28 Nov, 2019
Published
28 Nov, 2019