CVE-2011-1093
Description
From CVE.org
The dccp_rcv_state_process function in net/dccp/input.c in the Datagram Congestion Control Protocol (DCCP) implementation in the Linux kernel before 2.6.38 does not properly handle packets for a CLOSED endpoint, which allows remote attackers to cause a denial of service (NULL pointer dereference and OOPS) by sending a DCCP-Close packet followed by a DCCP-Reset packet.
Statement
This issue did not affect the version of Linux kernel as shipped with Red Hat Enterprise Linux 4 as it did not include support for the DCCP protocol. Future updates in Red Hat Enterprise Linux 5, 6 and Red Hat Enterprise MRG may address this flaw.
Mitigation
For users that do not run applications that use DCCP, you can prevent the dccp
module from being loaded by adding the following entry to the end of the
/etc/modprobe.d/blacklist file:
blacklist dccp
This way, the dccp module cannot be loaded accidentally, which may occur if an
application that requires DCCP is started. A reboot is not necessary for this
change to take effect but do make sure the module is not loaded in the first
place. You can verify that by running:
lsmod | grep dccp
You may also consider removing the CAP_SYS_MODULE capability from the current
global capability set to prevent kernel modules from being loaded or unloaded.
The CAP_SYS_MODULE has a capability number of 16 (see linux/capability.h). The
default value has all the bits set. To remove this capability, you have to
clear the 16th bit of the default 32-bit value, e.g. 0xffffff ^ (1 << 16):
echo 0xFFFEFFFF > /proc/sys/kernel/cap-bound
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 | 7.8 | 7.8 | N/A |
| Attack Vector | Network | Network | N/A |
| Access Complexity | Low | Low | N/A |
| Authentication | None | None | N/A |
| Confidentiality Impact | None | None | N/A |
| Integrity Impact | None | None | N/A |
| Availability Impact | Complete | Complete | N/A |
Vector
Red Hat: AV:N/AC:L/Au:N/C:N/I:N/A:C
NVD: AV:N/AC:L/Au:N/C:N/I:N/A:C
Understanding the Weakness (CWE)
Availability
Technical Impact: DoS: Crash, Exit, or Restart
NULL pointer dereferences usually result in the failure of the process unless exception handling (on some platforms) is available and implemented. Even when exception handling is being used, it can still be very difficult to return the software to a safe state of operation.
Integrity,Confidentiality
Technical Impact: Execute Unauthorized Code or Commands; Read Memory; Modify Memory
In rare circumstances, when NULL is equivalent to the 0x0 memory address and privileged code can access it, then writing or reading memory is possible, which may lead to code execution.
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