Comment 27 for bug 1206081

New attempt at impact description:

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Title: Potential Nova denial of service through compressed disk images
Reporter: Bernhard M. Wiedemann (SUSE)
Products: Nova
Affects: All versions

Description:
Bernhard M. Wiedemann from SUSE reported a vulnerability in Nova's control of the size of disk images. By using malicious compressed qcow2 disk images, an authenticated user may consume large amounts of disk space for each image, potentially resulting in a Denial of Service attack on Nova compute nodes. While fixing this issue, Pádraig Brady from Red Hat additionally discovered that OSSA 2013-012 did not fully address CVE-2013-2096 in the non-default case where use_cow_images=False, and malicious qcow images are being transferred from Glance. In that specific case, an authenticated user could still consume large amounts of disk space for each instance using the malicious image, potentially also resulting in a Denial of Service attack on Nova compute nodes. The provided fixes address both issues.
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