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CVE-2015-5166

18
FAUCET Score

CVE-2015-5166 describes a use-after-free vulnerability in QEMU, specifically within Xen 4.5.x and earlier, where emulated block devices are not completely unplugged. This flaw allows local HVM guest users to escalate privileges by repeatedly unplugging a block device. With a CVSS score of 7.2, this vulnerability is considered high severity, requiring local access with low attack complexity, and potentially leading to complete compromise of confidentiality, integrity, and availability. While there is no known active exploitation, public exploit code (Metasploit, Nuclei, ExploitDB) is unavailable, and community discussion and media coverage are minimal, suggesting limited current attention.

Impacted Technologies

VendorProductVersion(s)CPE
21CPE matchmatch criteria
cpe:2.3:o:fedoraproject:fedora:21:*:*:*:*:*:*:*
22CPE matchmatch criteria
cpe:2.3:o:fedoraproject:fedora:22:*:*:*:*:*:*:*
<= 4.5.0CPE matchmatch criteria
cpe:2.3:o:xen:xen:*:*:*:*:*:*:*:*
4.5.1CPE matchmatch criteria
cpe:2.3:o:xen:xen:4.5.1:*:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 2.0

7.2HIGH

AV:L/AC:L/Au:N/C:C/I:C/A:C

Confidentiality Impact
COMPLETE
Integrity Impact
COMPLETE
Availability Impact
COMPLETE
Access Vector
LOCAL
Access Complexity
LOW
Authentication
NONE
Exploitability Score
3.9
Impact Score
10.0
CvssVersion
2.0

Exploit Intelligence

EPSS Score
0.43%
Probability of exploitation in next 30 days
EPSS Percentile
34.9%
Percentile rank of EPSS score among Peer Group
As of 2026-07-27
Model: v2026.06.15
This CVE's current EPSS score of 0.0043 is in the 51st percentile among its peer group of 3,237 CVEs.

Social Chatter

No social media mentions found for this CVE.

The average CVE in this peer group has 0.0 Twitter, 0.0 Reddit, 0.1 Bluesky, 0.0 Mastodon, and 0.5 GitHub mentions.

Media Mentions

The average CVE in this peer group has 0.1 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Vendor Advisories (1)

redhatCVE-2015-5166Moderate

Qemu: BlockBackend object use after free issue (XSA-139)

Aug 3, 2015

References

lists.fedoraproject.org / pipermail/package-announce/2015-September/165373.html
lists.fedoraproject.org / pipermail/package-announce/2015-September/167792.html
lists.fedoraproject.org / pipermail/package-announce/2015-September/167820.html
securityfocus.com / bid/76152
securitytracker.com / id/1033175
xenbits.xen.org / xsa/advisory-139.html
PatchVendor Advisory