L3 CPU shared cache architecture is susceptible to a Flush+Reload side-channel attack

Overview

L3 CPU shared cache architecture is susceptible to a Flush+Reload side-channel attack, resulting in information leakage. allowing a local attacker to derive the contents of memory not belonging to the attacker.

Description

Common L3 CPU shared cache architecture is susceptible to a Flush+Reload side-channel attack, as described in “Flush+Reload: a High Resolution, Low Noise, L3 Cache Side-Channel Attack” by Yarom and Falkner.

By manipulating memory stored in the L3 cache by a target process and observing timing differences between requests for cached and non-cached memory, an attacker can derive specific information about the target process. The paper demonstrates an attack against GnuPG on an Intel Ivy Bridge platform that recovers over 98% of the bits of an RSA private key.

This vulnerability is an example of CWE-200: Information Exposure.

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Impact

A local attacker can derive the contents of memory shared with another process on the same L3 cache (same physical CPU). Virtualization and cryptographic software are examples that are likely to be vulnerable.

An attacker on the same host operating system only needs read access to the executable file or a shared library component of the target process.

An attacker on a different virtual machine similarly needs access to an exact copy of the executable or shared library used by the target process, and the hypervisor needs to have memory page de-duplication enabled.

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Solution

Apply an Update
See the Vendor Information section below for additional information.

GnuPG has released GnuPG version 1.4.14 and Libgcrypt 1.5.3 to to address this vulnerability. CVE-2013-4242 has been assigned to the specific GnuPG vulnerability described in the Yarom/Falkner paper. The CVSS score below applies specifically to CVE-2013-4242.

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Disable Memory Page De-duplication

To prevent this attack on virtualization platforms, disable hypervisor memory page de-duplication.

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Vendor Information

Any shared cache architecture may be susceptible to side-channel or timing attacks. CPU vendors are listed as “Not Affected” since the cache architecture is functioning as designed. It is generally up to an operating system or application to take appropriate measures to protect sensitive information.

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976534

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Linux KVM Affected

Notified: August 15, 2013 Updated: August 16, 2013

Status

Affected

Vendor Statement

We have not received a statement from the vendor.

Vendor Information

We are not aware of further vendor information regarding this vulnerability.

Red Hat, Inc. Affected

Notified: September 13, 2013 Updated: September 13, 2013

Status

Affected

Vendor Statement

We have not received a statement from the vendor.

Vendor Information

We are not aware of further vendor information regarding this vulnerability.

Vendor References

• <https://bugzilla.redhat.com/show_bug.cgi?id=988589&gt;

VMware Affected

Notified: August 16, 2013 Updated: September 03, 2013

Status

Affected

Vendor Statement

We have not received a statement from the vendor.

Vendor Information

We are not aware of further vendor information regarding this vulnerability.

Xen Affected

Notified: August 16, 2013 Updated: September 03, 2013

Status

Affected

Vendor Statement

We have not received a statement from the vendor.

Vendor Information

We are not aware of further vendor information regarding this vulnerability.

libgcrypt Affected

Notified: August 16, 2013 Updated: August 16, 2013

Status

Affected

Vendor Statement

We have not received a statement from the vendor.

Vendor Information

We are not aware of further vendor information regarding this vulnerability.

AMD __ Not Affected

Notified: August 16, 2013 Updated: October 29, 2013

Status

Not Affected

Vendor Statement

We have not received a statement from the vendor.

Vendor Information

We are not aware of further vendor information regarding this vulnerability.

Addendum

AMD generally uses an exclusive cache architecture and is therefore not vulnerable to this specific attack.

If you have feedback, comments, or additional information about this vulnerability, please send us [email](<mailto:[email protected]?Subject=VU%23976534 Feedback>).

Cryptlib Not Affected

Notified: August 16, 2013 Updated: September 03, 2013

Status

Not Affected

Vendor Statement

We have not received a statement from the vendor.

Vendor Information

We are not aware of further vendor information regarding this vulnerability.

GnuTLS Not Affected

Notified: August 16, 2013 Updated: September 03, 2013

Status

Not Affected

Vendor Statement

We have not received a statement from the vendor.

Vendor Information

We are not aware of further vendor information regarding this vulnerability.

Intel Corporation Not Affected

Notified: August 16, 2013 Updated: September 03, 2013

Status

Not Affected

Vendor Statement

We have not received a statement from the vendor.

Vendor Information

We are not aware of further vendor information regarding this vulnerability.

OpenSSL Not Affected

Notified: August 16, 2013 Updated: September 03, 2013

Status

Not Affected

Vendor Statement

We have not received a statement from the vendor.

Vendor Information

We are not aware of further vendor information regarding this vulnerability.

Amazon Unknown

Notified: August 16, 2013 Updated: September 03, 2013

Status

Unknown

Vendor Statement

We have not received a statement from the vendor.

Vendor Information

We are not aware of further vendor information regarding this vulnerability.

Attachmate Unknown

Notified: August 16, 2013 Updated: September 03, 2013

Status

Unknown

Vendor Statement

We have not received a statement from the vendor.

Vendor Information

We are not aware of further vendor information regarding this vulnerability.

Certicom Unknown

Notified: August 16, 2013 Updated: August 16, 2013

Status

Unknown

Vendor Statement

We have not received a statement from the vendor.

Vendor References

Crypto++ Library Unknown

Notified: August 16, 2013 Updated: August 16, 2013

Status

Unknown

Vendor Statement

We have not received a statement from the vendor.

Vendor References

EMC Corporation Unknown

Notified: August 16, 2013 Updated: August 16, 2013

Status

Unknown

Vendor Statement

We have not received a statement from the vendor.

Vendor References

IAIK Java Group Unknown

Notified: August 16, 2013 Updated: August 16, 2013

Status

Unknown

Vendor Statement

We have not received a statement from the vendor.

Vendor References

Microsoft Corporation Unknown

Notified: August 16, 2013 Updated: August 16, 2013

Status

Unknown

Vendor Statement

We have not received a statement from the vendor.

Vendor References

Oracle Corporation Unknown

Notified: August 16, 2013 Updated: August 16, 2013

Status

Unknown

Vendor Statement

We have not received a statement from the vendor.

Vendor References

Parallels Holdings Ltd Unknown

Notified: August 16, 2013 Updated: August 16, 2013

Status

Unknown

Vendor Statement

We have not received a statement from the vendor.

Vendor References

QEMU Unknown

Notified: August 16, 2013 Updated: August 16, 2013

Status

Unknown

Vendor Statement

We have not received a statement from the vendor.

Vendor References

SafeNet Unknown

Notified: August 16, 2013 Updated: August 16, 2013

Status

Unknown

Vendor Statement

We have not received a statement from the vendor.

Vendor References

Spyrus Unknown

Notified: August 16, 2013 Updated: August 16, 2013

Status

Unknown

Vendor Statement

We have not received a statement from the vendor.

Vendor References

lsh Unknown

Notified: August 16, 2013 Updated: August 16, 2013

Status

Unknown

Vendor Statement

We have not received a statement from the vendor.

Vendor References

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CVSS Metrics

Group	Score	Vector
Base	2.4	AV:L/AC:H/Au:S/C:P/I:P/A:N
Temporal	1.9	E:POC/RL:OF/RC:C
Environmental	2.3	CDP:ND/TD:M/CR:H/IR:H/AR:ND

References

• <http://eprint.iacr.org/2013/448.pdf&gt;
• <http://cwe.mitre.org/data/definitions/200.html&gt;
• <http://lists.gnupg.org/pipermail/gnupg-announce/2013q3/000330.html&gt;
• <http://lists.gnupg.org/pipermail/gnupg-announce/2013q3/000329.html&gt;

Acknowledgements

Thanks to Yuval Yarom and Katrina Falkner for reporting this vulnerability and for help writing this document.

This document was written by Adam Rauf.

Other Information

CVE IDs:	CVE-2013-4242
Date Public:	2013-09-05 Date First Published: