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CVE-2021-20286

15
FAUCET Score

CVE-2021-20286 is a low-severity denial-of-service vulnerability affecting libnbd versions up to 1.7.3, specifically impacting Red Hat Enterprise Linux and libnbd. The flaw, an assertion failure in nbd_unlocked_opt_go, can be triggered remotely with low attack complexity by a high-privileged attacker, leading to a denial of service. There is no evidence of active exploitation, public exploit code, or significant community discussion surrounding this CVE.

Impacted Technologies

VendorProductVersion(s)CPE
< 1.7.3CPE matchmatch criteria
cpe:2.3:a:redhat:libnbd:*:*:*:*:*:*:*:*
8.3.0CPE matchmatch criteria
cpe:2.3:o:redhat:enterprise_linux:8.3.0:*:*:*:advanced_virtualization:*:*:*

CVSS Data

CVSS version used by this source: 3.1

2.7LOW

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

Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
HIGH
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
NONE
Integrity Impact
NONE
Availability Impact
LOW
Exploitability Score
1.2
Impact Score
1.4
CvssVersion
3.1

Exploit Intelligence

EPSS Score
1.14%
Probability of exploitation in next 30 days
EPSS Percentile
63.2%
Percentile rank of EPSS score among Peer Group
As of 2026-07-27
Model: v2026.06.15
This CVE's current EPSS score of 0.0114 is in the 90th percentile among its peer group of 708 CVEs.

Social Chatter

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

Media Mentions

No media coverage found for this CVE.

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

Remediation

Patch Available

Vendor Patches (8)

microsoftpatch availablevia msrc
Product: azl3 libnbd 1.18.3-1 on Azure Linux 3.0Fixed in: 1.18.3-1
microsoftpatch availablevia msrc
Product: 19076-17084Fixed in: 1.18.3-1
microsoftpatch availablevia msrc
Product: azl3 libnbd 1.12.1-3 on Azure Linux 3.0Fixed in: 1.18.3-1
microsoftpatch availablevia msrc
Product: 18302-17084Fixed in: 1.18.3-1
microsoftpatch availablevia msrc
Product: CBL Mariner 2.0 x64Fixed in: 1.12.1-1
microsoftpatch availablevia msrc
Product: CBL Mariner 2.0 ARMFixed in: 1.12.1-1
redhatvendor investigatingvia redhat_api
Product: Red Hat Enterprise Linux 8 Advanced VirtualizationFixed in: virt:8.3/libnbd
redhatno patchvia redhat_api
Product: Red Hat Enterprise Linux 8 Advanced VirtualizationFixed in: virt:av/libnbd

Vendor Advisories (5)

microsoft2024-Dec/CVE-2021-20286

CVE-2021-20286

Dec 10, 2024
microsoft2024-Nov/CVE-2021-20286

CVE-2021-20286

Nov 12, 2024
microsoft2024-Oct/CVE-2021-20286

CVE-2021-20286

Oct 8, 2024
microsoft2021-Mar/CVE-2021-20286Low

A flaw was found in libnbd 1.7.3. An assertion failure in nbd_unlocked_opt_go in ilb/opt.c may lead to denial of service.

Mar 9, 2021
redhatCVE-2021-20286Low

libnbd: Assertion failure in nbd_unlocked_opt_go in lib/opt.c

Mar 1, 2021

References

bugzilla.redhat.com / show_bug.cgi
Issue TrackingThird Party Advisory
gitlab.com / nbdkit/libnbd/-/commit/fb4440de9cc76e9c14bd3ddf3333e78621f40ad0
PatchThird Party Advisory