The vulnerable system is bound to the network stack and the set of possible attackers extends beyond the other options listed below, up to and including the entire Internet. Such a vulnerability is often termed “remotely exploitable” and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers). An example of a network attack is an attacker causing a denial of service by sending a specially crafted TCP packet across a wide area network (e.g., CVE-2004-0230).
Attack Complexity
Low
AC
The attacker must take no measurable action to exploit the vulnerability. The attack requires no target-specific circumvention to exploit the vulnerability. An attacker can expect repeatable success against the vulnerable system.
Privileges Required
None
PR
The attacker is unauthenticated prior to attack, and therefore does not require any access to settings or files of the vulnerable system to carry out an attack.
User Interaction
None
UI
The vulnerable system can be exploited without interaction from any human user, other than the attacker. Examples include: a remote attacker is able to send packets to a target system a locally authenticated attacker executes code to elevate privileges
Scope
Unchanged
S
An exploited vulnerability can only affect resources managed by the same security authority. In the case of a vulnerability in a virtualized environment, an exploited vulnerability in one guest instance would not affect neighboring guest instances.
Confidentiality
High
C
There is total information disclosure, resulting in all data on the system being revealed to the attacker, or there is a possibility of the attacker gaining control over confidential data.
Integrity
High
I
There is a total compromise of system integrity. There is a complete loss of system protection, resulting in the attacker being able to modify any file on the target system.
Availability
High
A
There is a total shutdown of the affected resource. The attacker can deny access to the system or data, potentially causing significant loss to the organization.
Below is a copy: GNU Mailutils 3.7 Privilege Escalation
# Exploit Title: GNU Mailutils 3.7 - Local Privilege Escalation
# Date: 2019-11-06
# Exploit Author: Mike Gualtieri
# Vendor Homepage: https://mailutils.org/
# Software Link: https://ftp.gnu.org/gnu/mailutils/mailutils-3.7.tar.gz
# Version: 2.0 <= 3.7
# Tested on: Gentoo
# CVE : CVE-2019-18862
Title : GNU Mailutils / Maidag Local Privilege Escalation
Author : Mike Gualtieri :: https://www.mike-gualtieri.com
Date : 2019-11-06
Updated : 2019-11-20
Vendor Affected: GNU Mailutils :: https://mailutils.org/
Versions Affected: 2.0 - 3.7
CVE Designator: CVE-2019-18862
1. Overview
The --url parameter included in the GNU Mailutils maidag utility (versions 2.0
through 3.7) can abused to write to arbitrary files on the host operating
system. By default, maidag is set to execute with setuid root permissions,
which can lead to local privilege escalation through code/command execution by
writing to the system's crontab or by writing to other root owned files on the
operating system.
2. Detail
As described by the project's homepage, "GNU Mailutils is a swiss army knife of
electronic mail handling. It offers a rich set of utilities and daemons for
processing e-mail".
Maidag, a mail delivery agent utility included in the suite, is by default
marked to execute with setuid (suid) root permissions.
The --url parameter of maidag can be abused to write to arbitrary files on the
operating system. Abusing this option while the binary is marked with suid
permissions allows a low privileged user to write to arbitrary files on the
system as root. Writing to the crontab, for example, may lead to a root shell.
The flaw itself appears to date back to the 2008-10-19 commit, when the --url
parameter was introduced to maidag.
11637b0f - New maidag mode: --url
https://git.savannah.gnu.org/cgit/mailutils.git/commit/?id=11637b0f262db62b4dc466cefb9315098a1a995a
maidag/Makefile.am:
chmod 4755 $(DESTDIR)$(sbindir)/$$i;\
The following payload will execute arbitrary commands as root and works with
versions of maidag, through version 3.7.
maidag --url /etc/crontab < /tmp/crontab.in
The file /tmp/crontab.in would contain a payload like the following.
line 1:
line 2: */1 * * * * root /tmp/payload.sh
Please note: For the input to be accepted by maidag, the first line of the
file must be blank or be commented.
In the above example, the file /tmp/payload.sh would include arbitrary
commands to execute as root.
Older versions of GNU Mailutils (2.2 and previous) require a different syntax:
maidag --url 'mbox://user@localhost //etc/crontab' < /tmp/crontab.in
3. Solution
A fix for the flaw has been made in GNU Mailutils 3.8, which removes the maidag
utility, and includes three new utilities that replace its functionality.
Details about the new features can be found in the project's release notes:
https://git.savannah.gnu.org/cgit/mailutils.git/tree/NEWS
Another workaround for those unable to upgrade, is to remove the suid bit on
/usr/sbin/maidag (e.g. `chmod u-s /usr/sbin/maidag`).
It should be noted that some Linux distributions already remove the suid bit
from maidag by default, nullifying this privilege escalation flaw.
Another patch has been made available by Sergey Poznyakoff and posted to the
GNU Mailutils mailing list, which removes the setuid bit for maidag in all but
required cases. The patch is intended for users who can not yet upgrade to
mailutils 3.8. The patch has also been made available here:
https://www.mike-gualtieri.com/files/maidag-dropsetuid.patch
4. Additional Comments
This vulnerability disclosure was submitted to MITRE Corporation for inclusion
in the Common Vulnerabilities and Exposures (CVE) database. The designator
CVE-2019-18862 has been assigned.
https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2019-18862
https://nvd.nist.gov/vuln/detail/CVE-2019-18862
The NIST National Vulnerability Database (NVD) has assigned the following
ratings:
CVSS 3.x Severity and Metrics: Base Score: 7.8 HIGH
CVSS 2.0 Severity and Metrics: Base Score: 4.6 MEDIUM
This disclosure will be updated as new information becomes available.
5. History
2019-10-09 Informed Sergey Poznyakoff <[email protected]> of security issue
2019-10-10 Reply from Sergey acknowledging the issue
2019-10-12 Fix available in the GNU Mailutils git repository:
739c6ee5 - Split maidag into three single-purpose tools
https://git.savannah.gnu.org/cgit/mailutils.git/commit/?id=739c6ee525a4f7bb76b8fe2bd75e81a122764ced
2019-11-06 GNU Mailutils Version 3.8 released to close the issue
2019-11-06 Submission of this vulnerability disclosure to MITRE Corporate to
obtain a CVE designator
2019-11-07 Patch offered by Sergey for those unable to upgrade to version 3.8
2019-11-11 CVE-2019-18862 assigned to flaw
2019-11-20 Vulnerability disclosure made publicly available
This information is provided for TESTING and LEGAL RESEARCH purposes only. All trademarks used are properties of their respective owners. By visiting this website you agree to Terms of Use and Privacy Policy and Impressum