A flaw was found in the way the pppol2tp_setsockopt() and pppol2tp_getsockopt() functions in the Linux kernel's PPP over L2TP implementation handled requests with a non-SOL_PPPOL2TP socket option level. A local, unprivileged user could use this flaw to escalate their privileges on the system.
Find out more about CVE-2014-4943 from the MITRE CVE dictionary dictionary and NIST NVD.
This issue does not affect the Linux kernel packages as shipped with Red Hat
Enterprise Linux 5 and Red Hat Enterprise MRG 2.
Please note that on Red Hat Enterprise Linux 6 pppol2tp module is not
automatically loaded when AF_PPPOX/PX_PROTO_OL2TP socket is created as
Red Hat Enterprise Linux 6 lacks upstream commit 9395a09d05a23bb and default
modprobe configuration as shipped with module-init-tools package does not
contain the alias for pppol2tp protocol either. As a result, pppol2tp module
has to be explicitly enabled and/or loaded by the system administrator.
| Base Score | 7.2 |
|---|---|
| Base Metrics | AV:L/AC:L/Au:N/C:C/I:C/A:C |
| Access Vector | Local |
| Access Complexity | Low |
| Authentication | None |
| Confidentiality Impact | Complete |
| Integrity Impact | Complete |
| Availability Impact | Complete |
Find out more about Red Hat support for the Common Vulnerability Scoring System (CVSS).
| Platform | Errata | Release Date |
|---|---|---|
| Red Hat Enterprise Linux Extended Update Support 6.4 (kernel) | RHSA-2014:0925 | 2014-07-23 |
| Red Hat Enterprise Linux Advanced Update Support 6.2 (kernel) | RHSA-2014:1025 | 2014-08-06 |
| Red Hat Enterprise Linux 7 (kernel) | RHSA-2014:0923 | 2014-07-23 |
| Red Hat Enterprise Linux 6 (kernel) | RHSA-2014:0924 | 2014-07-23 |
| Platform | Package | State |
|---|---|---|
| Red Hat Enterprise MRG 2 | realtime-kernel | Not affected |
| Red Hat Enterprise Linux 5 | kernel | Not affected |
For Red Hat Enterprise Linux 6 do --
]# echo "install pppol2tp /bin/true" > /etc/modprobe.d/pppol2tp.conf
For Red Hat Enterprise Linux 7 do --
]# echo "install l2tp_ppp /bin/true" > /etc/modprobe.d/l2t_pppp.conf
Or, alternatively, when pppol2tp/l2tp_ppp module can't be blacklisted and needs
to be loaded, you can use the following systemtap script --
1) On the host, save the following in a file with the ".stp" extension --
probe module("*l2tp*").function("pppol2tp_*etsockopt").call {
$level = 273;
}
2) Install the "systemtap" package and any required dependencies. Refer to
the "2. Using SystemTap" chapter in the Red Hat Enterprise Linux 6
"SystemTap Beginners Guide" document, available from docs.redhat.com, for
information on installing the required -debuginfo packages.
3) Run the "stap -g [filename-from-step-1].stp" command as root.
If the host is rebooted, the changes will be lost and the script must be
run again.
Alternatively, build the systemtap script on a development system with
"stap -g -p 4 [filename-from-step-1].stp", distribute the resulting kernel
module to all affected systems, and run "staprun -L <module>" on those.
When using this approach only systemtap-runtime package is required on the
affected systems. Please notice that the kernel version must be the same across
all systems.
Vulmon