GHOST: glibc vulnerability (CVE-2015-0235)
Red Hat Product Security has been made aware of a critical vulnerability in the glibc library, which has been assigned CVE-2015-0235 and is commonly referred to as 'GHOST'. All versions of glibc shipped with all variants of Red Hat Enterprise Linux are affected.
Background Information
GHOST is a 'buffer overflow' bug affecting the gethostbyname() and gethostbyname2() function calls in the glibc library. This vulnerability allows a remote attacker that is able to make an application call to either of these functions to execute arbitrary code with the permissions of the user running the application.
Impact
The gethostbyname() function calls are used for DNS resolving, which is a very common event. To exploit this vulnerability, an attacker must trigger a buffer overflow by supplying an invalid hostname argument to an application that performs a DNS resolution.
Determining Vulnerability
As a Red Hat customer, the easiest way to check for the vulnerability and confirm remediation is the Red Hat Access Lab: glibc (GHOST) Detector. Please make sure that you have installed the correct version prior and if you are downloading the package for RHEL 4, you must be subscribed to the ELS channel or have downloaded the ELS version of the package. The RHEL 4 non-ELS subscription version will show a "vulnerable" message.
Resolution
To eliminate the possibility of an exploit:
1. Update the glibc and nscd packages on your system using the packages released with the following errata:
- Red Hat Enterprise Linux Server 5: RHSA-2015:0090
- Red Hat Enterprise Linux Server (v. 6): RHSA-2015:0092
- Red Hat Enterprise Linux Server (v. 7): RHSA-2015:0092
- Red Hat Enterprise Linux Desktop 5: RHSA-2015:0090
- Red Hat Enterprise Linux Desktop 6: RHSA-2015:0092
- Red Hat Enterprise Linux Desktop 7: RHSA-2015:0092
- Red Hat Enterprise Linux HPC Node 6: RHSA-2015:0092
- Red Hat Enterprise Linux HPC Node 7: RHSA-2015:0092
- Red Hat Enterprise Linux Workstation 6: RHSA-2015:0092
- Red Hat Enterprise Linux Workstation 7: RHSA-2015:0092
- Red Hat Enterprise Linux Server EUS (v. 6.6): RHSA-2015:0092
- Red Hat Enterprise Linux Server EUS (v. 6.5): RHSA-2015:0099
- Red Hat Enterprise Linux Server EUS (v. 6.4): RHSA-2015:0099
- Red Hat Enterprise Linux Server EUS (v. 5.9): RHSA-2015:0099
- Red Hat Enterprise Linux ELS (v. 4): RHSA-2015:0101
- An active ELS subscription is required for access to this patch in RHEL 4. (What is the Red Hat Enterprise Linux Extended Life Cycle Support Add-On (ELS)?)
- Please contact Red Hat sales or your specific sales representative for more information if your account does not have an active ELS subscription: Contact Sales.
2. Reboot the system or restart all affected services:
Because this vulnerability affects a large amount of applications on the system, the safest and recommended way to assure every application uses the updated glibc packages is to restart the system.
In case you are unable to restart the entire system after applying the update, execute the following command to list all running processes (not restricted to services) still using the old [in-memory] version of glibc on your system.
lsof +c0 -d DEL | awk 'NR==1 || /libc-/ {print $2,$1,$4,$NF}' | column -t
From the resulting list, identify the public-facing services and restart them. While this process may work as a temporary workaround, it is not supported by Red Hat and, should a problem arise, you will be requested to reboot the system before any troubleshooting begins.
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