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CVE-2019-18276

Publication date 28 November 2019

Last updated 24 July 2024

Ubuntu priority

Low

Why this priority?

Cvss 3 Severity Score

7.8 · High

Score breakdown

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.

Read the notes from the security team

Status

Package Ubuntu Release Status
bash 22.04 LTS jammy
Not affected
21.10 impish
Not affected
21.04 hirsute
Not affected
20.10 groovy Ignored
20.04 LTS focal
Fixed 5.0-6ubuntu1.2
19.10 eoan Ignored
19.04 disco Ignored
18.04 LTS bionic
Fixed 4.4.18-2ubuntu1.3
16.04 LTS xenial
14.04 LTS trusty

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Notes

sbeattie

This issue appears to only affect bash when bash is setuid. Ubuntu does not ship with bash setuid, so this has minimal impact for Ubuntu users. This is why we have rated the priority for this issue 'low'. reproducer steps in the suse bugzilla

Patch details

For informational purposes only. We recommend not to cherry-pick updates. How can I get the fixes?

Package Patch details
bash

Severity score breakdown

Parameter Value
Base score 7.8 · High
Attack vector Local
Attack complexity Low
Privileges required Low
User interaction None
Scope Unchanged
Confidentiality High
Integrity impact High
Availability impact High
Vector CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

References

Related Ubuntu Security Notices (USN)

Other references