CVE-2015-7504
Description
A heap-based buffer overflow flaw was discovered in the way QEMU's AMD PC-Net II Ethernet Controller emulation received certain packets in loopback mode. A privileged user (with the CAP_SYS_RAWIO capability) inside a guest could use this flaw to crash the host QEMU process (resulting in denial of service) or, potentially, execute arbitrary code with privileges of the host QEMU process.
Statement
This issue does not affect the versions of the qemu-kvm packages as shipped with Red Hat Enterprise Linux 7 as they do not enable the pcnet backend driver.
This issue does not affect the Red Hat Enterprise Linux 7 based versions of the qemu-kvm-rhev packages as shipped with Red Hat Enterprise Virtualization 3.
This issue affects the versions of the kvm and xen packages as shipped with Red Hat Enterprise Linux 5, the versions of the qemu-kvm packages as shipped with Red Hat Enterprise Linux 6, and the Red Hat Enterprise Linux 6 based versions of qemu-kvm-rhev packages as shipped with Red Hat Enterprise Virtualization 3. Future updates for the respective releases may address this flaw.
Please note that AMD PCNet adapter has to be explicitly enabled per-guest as it is not enabled in default configuration and is not supported by Red Hat in Red Hat Enterprise Linux 6 (for a list of supported devices please consult https://access.redhat.com/documentation/en-US/Red_Hat_Enterprise_Linux/6/html/Virtualization_Administration_Guide/sect-whitelist-device-options.html).
Red Hat Enterprise Linux 5 is now in Production 3 Phase of the support and maintenance life cycle. Though this has been rated as having Important security impact and is not currently planned to be addressed in future updates. For additional information, refer to the Red Hat Enterprise Linux Life Cycle: https://access.redhat.com/support/policy/updates/errata/.
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 | 6.5 | 4.6 | N/A |
| Attack Vector | Adjacent Network | Local | N/A |
| Access Complexity | High | Low | N/A |
| Authentication | Single | None | N/A |
| Confidentiality Impact | Complete | Partial | N/A |
| Integrity Impact | Complete | Partial | N/A |
| Availability Impact | Complete | Partial | N/A |
Vector
Red Hat: AV:A/AC:H/Au:S/C:C/I:C/A:C
NVD: AV:L/AC:L/Au:N/C:P/I:P/A:P
Understanding the Weakness (CWE)
Availability
Technical Impact: DoS: Crash, Exit, or Restart; DoS: Resource Consumption (CPU); DoS: Resource Consumption (Memory)
Buffer overflows generally lead to crashes. Other attacks leading to lack of availability are possible, including putting the program into an infinite loop.
Integrity,Confidentiality,Availability,Access Control
Technical Impact: Execute Unauthorized Code or Commands; Bypass Protection Mechanism; Modify Memory
Buffer overflows often can be used to execute arbitrary code, which is usually outside the scope of a program's implicit security policy. Besides important user data, heap-based overflows can be used to overwrite function pointers that may be living in memory, pointing it to the attacker's code. Even in applications that do not explicitly use function pointers, the run-time will usually leave many in memory. For example, object methods in C++ are generally implemented using function pointers. Even in C programs, there is often a global offset table used by the underlying runtime.
Integrity,Confidentiality,Availability,Access Control,Other
Technical Impact: Execute Unauthorized Code or Commands; Bypass Protection Mechanism; Other
When the consequence is arbitrary code execution, this can often be used to subvert any other security service.
Acknowledgements
Red Hat would like to thank Ling Liu (Qihoo 360 Inc) and Qinghao Tang (QIHU 360 Marvel Team) for reporting this issue.
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