CVE-2021-20286

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.

Published: 2021-03-15 Last update: 2026-06-16 Assigner: [email protected] Source: [email protected]
NVD Status：Modified，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2021-20286 is rated Low Risk (33.2/100): CVSS Low severity, with medium exploitation likelihood (EPSS 1.11%). Monitor for updates and reassess as exploit intelligence or EPSS changes.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Exploit prediction scoring system (EPSS) score for CVE-2021-20286

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-06-15 0.25% 1.11% +0.87%
2 2026-03-22 0.39% 0.25% -0.14%
3 2025-11-21 — 0.39% —

Full EPSS history (14 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2021-20286

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
2.7 3.1 LOW
CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:L Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:H)
They need powerful rights—admin, root, or similar—before this pays off.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:N)
Doesn’t really leak secrets in a meaningful way.
Integrity (I:N)
Data isn’t meaningfully altered or forged.
Availability (A:L)
Might cause slowdowns, glitches, or partial disruption—not a full brick.
 1.2 1.4 [email protected]
4.0 2.0 MEDIUM
AV:N/AC:L/Au:S/C:N/I:N/A:P Click to expand
Access vector (AV:N)
Can be exploited remotely over network reachability.
Access complexity (AC:L)
Exploitation conditions are straightforward and predictable.
Authentication (AU:S)
A single authentication is required.
Confidentiality impact (C:N)
No confidentiality impact.
Integrity impact (I:N)
No integrity impact.
Availability impact (A:P)
Partial availability impact.
 8.0 2.9 [email protected]

Weakness enumeration for CVE-2021-20286

OS Trackers for CVE-2021-20286

vendor priority summary link
alpine low CVE-2021-20286: 1 source package rows (libnbd); 4 state rows across 4 repos (3.20-community, 3.21-community, 3.22-community, edge-community); fixed 4, open 0. https://security.alpinelinux.org/vuln/CVE-2021-20286
debian not yet assigned CVE-2021-20286 not yet assigned priority: Debian including 1 source packages (libnbd), 5 status rows across 5 suites (bookworm, bullseye, forky, sid, trixie): resolved 4, open 1. https://security-tracker.debian.org/tracker/CVE-2021-20286
redhat low — https://access.redhat.com/security/cve/CVE-2021-20286
ubuntu medium CVE-2021-20286 medium priority: Ubuntu including 1 source packages (libnbd), 16 status rows across 16 suites (bionic, focal, groovy, hirsute, impish, jammy, kinetic, lunar, mantic, noble, oracular, plucky, questing, trusty, upstream, xenial): not-affected 10, DNE 3, ignored 1, needs-triage 1, released 1. https://ubuntu.com/security/CVE-2021-20286

Affected software / configurations for CVE-2021-20286

Vendor Product Version Raw CPE
redhat libnbd < 1.7.3 cpe:2.3:a:redhat:libnbd:*:*:*:*:*:*:*:*
redhat enterprise_linux 8.3.0 cpe:2.3:o:redhat:enterprise_linux:8.3.0:*:*:*:advanced_virtualization:*:*:*

References for CVE-2021-20286

cvelogic Threat Intelligence