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CVE-2020-27675

19
FAUCET Score

CVE-2020-27675 describes a race condition in the Linux kernel (through 5.9.1) when used with Xen (through 4.14.x), specifically within the event-handling loop for paravirtualized devices. This flaw can lead to a use-after-free or NULL pointer dereference, potentially causing a dom0 crash. It is rated Medium severity (CVSS 4.7) due to its local attack vector and high impact on availability, though it requires high attack complexity and low privileges. There is currently no evidence of active exploitation, public exploit code (Metasploit, Nuclei, ExploitDB), or significant community discussion surrounding this vulnerability.

Impacted Technologies

VendorProductVersion(s)CPE
<= 5.9.1CPE matchmatch criteria
cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
31CPE matchmatch criteria
cpe:2.3:o:fedoraproject:fedora:31:*:*:*:*:*:*:*
32CPE matchmatch criteria
cpe:2.3:o:fedoraproject:fedora:32:*:*:*:*:*:*:*
33CPE matchmatch criteria
cpe:2.3:o:fedoraproject:fedora:33:*:*:*:*:*:*:*
9.0CPE matchmatch criteria
cpe:2.3:o:debian:debian_linux:9.0:*:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 3.1

4.7MEDIUM

CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H

Attack Vector
LOCAL
Attack Complexity
HIGH
Privileges Required
LOW
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
NONE
Integrity Impact
NONE
Availability Impact
HIGH
Exploitability Score
1.0
Impact Score
3.6
CvssVersion
3.1

Exploit Intelligence

EPSS Score
0.27%
Probability of exploitation in next 30 days
EPSS Percentile
18.9%
Percentile rank of EPSS score among Peer Group
As of 2026-07-28
Model: v2026.06.15
This CVE's current EPSS score of 0.0027 is in the 62nd percentile among its peer group of 1,297 CVEs.

Social Chatter

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

Media Mentions

No media coverage found for this CVE.

The average CVE in this peer group has 0.4 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Patch Available

Vendor Patches (5)

github_advisorypatch availablevia nvd_reference
View patch
microsoftpatch availablevia msrc
Product: 19137-16820Fixed in: 5.4.91-1
microsoftpatch availablevia msrc
Product: CBL Mariner 1.0 x64Fixed in: 5.4.91-1
microsoftpatch availablevia msrc
Product: CBL Mariner 1.0 ARMFixed in: 5.4.91-1
microsoftpatch availablevia msrc
Product: cm1 kernel 5.4.91-1 on CBL Mariner 1.0Fixed in: 5.4.91-1

Vendor Advisories (3)

microsoft2020-Nov/CVE-2020-27675

CVE-2020-27675

Nov 10, 2020
redhatCVE-2020-27675

kernel: xen: race condition in event-channel removal during the event-handling loop (XSA-331)

Oct 20, 2020
microsoft2020-Oct/CVE-2020-27675Moderate

An issue was discovered in the Linux kernel through 5.9.1 as used with Xen through 4.14.x. drivers/xen/events/events_base.c allows event-channel removal during the event-handling loop (a race condition). This can cause a use-after-free or NULL pointer dereference as demonstrated by a dom0 crash via events for an in-reconfiguration paravirtualized device aka CID-073d0552ead5.

Oct 13, 2020

References

github.com / torvalds/linux/commit/073d0552ead5bfc7a3a9c01de590e924f11b5dd2
PatchThird Party Advisory
git.kernel.org / cgit/linux/kernel/git/torvalds/linux.git/commit
PatchVendor Advisory
lists.debian.org / debian-lts-announce/2020/12/msg00015.html
Mailing ListThird Party Advisory
lists.debian.org / debian-lts-announce/2020/12/msg00027.html
Mailing ListThird Party Advisory
lists.fedoraproject.org / archives/list/package-announce%40lists.fedoraproject.org/message/3ZG6TZLD23QO3PV2AN2HB625ZX47ALTT
lists.fedoraproject.org / archives/list/package-announce%40lists.fedoraproject.org/message/6USZ4APZSBQDHGJLJMHW5JBN4QZV6SKZ
lists.fedoraproject.org / archives/list/package-announce%40lists.fedoraproject.org/message/GNF2R7FUT4IOJ2RIRGQ7X5R4F4FVVLSR
security.gentoo.org / glsa/202011-06
Third Party Advisory
xenbits.xen.org / xsa/advisory-331.html
PatchVendor Advisory
openwall.com / lists/oss-security/2021/01/19/3
Mailing ListThird Party Advisory