CVE-2015-3636
Description
It was found that the Linux kernel's ping socket implementation did not properly handle socket unhashing during spurious disconnects, which could lead to a use-after-free flaw. On x86-64 architecture systems, a local user able to create ping sockets could use this flaw to crash the system. On non-x86-64 architecture systems, a local user able to create ping sockets could use this flaw to escalate their privileges on the system.
Statement
This issue does not affect the Linux kernel as shipped with Red Hat Enterprise Linux 5. This issue does affect the Linux kernel as shipped with Red Hat Enterprise Linux 6, 7 and Red Hat Enterprise MRG 2. Future kernel updates for the respective releases will address this issue.
Please note that on x86-64 architecture systems the impact is limited to local Denial of Service and that the ping sockets functionality is disabled by default (net.ipv4.ping_group_range sysctl is "1 0").
Mitigation
You can check whether ping socket functionality is enabled by examining the net.ipv4.ping_group_range sysctl value:
~]# sysctl net.ipv4.ping_group_range
net.ipv4.ping_group_range = 1 0
"1 0" is the default value and disables the ping socket functionality even for root user. Any other value means that the ping socket functionality might be enabled for certain users on the system.
To mitigate this vulnerability make sure that you either allow the functionality to trusted local users (groups) only or set the net.ipv4.ping_group_range sysctl to the default and disabled state:
~]# sysctl net.ipv4.ping_group_range="1 0"
Please note that this might prevent some programs relying on this functionality from functioning properly.
Common Vulnerability Scoring System (CVSS) Score Details
Info alert:Important note
CVSS scores for open source components depend on vendor-specific factors (e.g. version or build chain). Therefore, Red Hat's score and impact rating can be different from NVD and other vendors. Red Hat remains the authoritative CVE Naming Authority (CNA) source for its products and services (see Red Hat classifications).
CVSS v2 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 6 | 4.9 | N/A |
| Attack Vector | Local | Local | N/A |
| Access Complexity | High | Low | N/A |
| Authentication | Single | None | N/A |
| Confidentiality Impact | Complete | None | N/A |
| Integrity Impact | Complete | None | N/A |
| Availability Impact | Complete | Complete | N/A |
Vector
Red Hat: AV:L/AC:H/Au:S/C:C/I:C/A:C
NVD: AV:L/AC:L/Au:N/C:N/I:N/A:C
Understanding the Weakness (CWE)
Integrity
Technical Impact: Modify Memory
The use of previously freed memory may corrupt valid data, if the memory area in question has been allocated and used properly elsewhere.
Availability
Technical Impact: DoS: Crash, Exit, or Restart
If chunk consolidation occurs after the use of previously freed data, the process may crash when invalid data is used as chunk information.
Confidentiality
Technical Impact: Read Memory
Read operations on freed memory can sometimes leak sensitive information instead of causing a crash
Integrity,Confidentiality,Availability
Technical Impact: Execute Unauthorized Code or Commands
If malicious data is entered before chunk consolidation can take place, it may be possible to take advantage of a write-what-where primitive to execute arbitrary code. If the newly allocated data happens to hold a class, in C++ for example, various function pointers may be scattered within the heap data. If one of these function pointers is overwritten with an address to valid shellcode, execution of arbitrary code can be achieved.
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