CVE-2021-3127

Exp

NATS Server 2.x before 2.2.0 and JWT library before 2.0.1 have Incorrect Access Control because Import Token bindings are mishandled.

Published: 2021-03-16 Last update: 2026-03-30 Assigner: [email protected] Source: [email protected]
NVD Status：Modified，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2021-3127 is rated High Exploit Risk (63.2/100): CVSS High severity, with medium exploitation likelihood (EPSS 0.29%). 1 public exploit reference(s) are indexed (Exploit-DB). Public exploits are available—assess exposure, apply mitigations, and prioritize patching.

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

Public exploit references (Exploit-DB) for CVE-2021-3127

EDB-ID Source Kind Published Link
— nvd_ref exploit_tag Exploit-DB ↗

Exploit prediction scoring system (EPSS) score for CVE-2021-3127

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 2025-07-03 0.41% 0.29% -0.12%
2 2025-03-30 1.40% 0.41% -0.99%
3 2025-03-29 — 1.40% —

Full EPSS history (10 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2021-3127

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
7.5 3.1 HIGH
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N 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:N)
No account or special rights needed—anonymous or random user is enough.
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:H)
Serious risk that confidential data gets exposed in a big way.
Integrity (I:N)
Data isn’t meaningfully altered or forged.
Availability (A:N)
Service keeps running; no real outage angle.
 3.9 3.6 [email protected]
5.0 2.0 MEDIUM
AV:N/AC:L/Au:N/C:P/I:N/A:N 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:N)
No authentication is required.
Confidentiality impact (C:P)
Partial confidentiality impact.
Integrity impact (I:N)
No integrity impact.
Availability impact (A:N)
No availability impact.
 10.0 2.9 [email protected]

Weakness enumeration for CVE-2021-3127

GitHub Security Advisory for CVE-2021-3127

GHSA-62mh-w5cv-p88c · Severity: critical · Ecosystem: go — nats-io/jwt not enforcing checking of Import token permissions

OS Trackers for CVE-2021-3127

vendor priority summary link
debian unimportant CVE-2021-3127 unimportant priority: Debian including 2 source packages (golang-github-nats-io-jwt, nats-server), 8 status rows across 4 suites (bookworm, forky, sid, trixie): resolved 8. https://security-tracker.debian.org/tracker/CVE-2021-3127
ubuntu medium CVE-2021-3127 medium priority: Ubuntu including 1 source packages (golang-github-nats-io-jwt), 16 status rows across 16 suites (bionic, focal, groovy, hirsute, impish, jammy, kinetic, lunar, mantic, noble, oracular, plucky, questing, trusty, upstream, xenial): ignored 6, not-affected 4, DNE 3, needed 2, released 1. https://ubuntu.com/security/CVE-2021-3127

Affected software / configurations for CVE-2021-3127

Vendor Product Version Raw CPE
linuxfoundation nats-server >= 2.0.0, < 2.2.0 cpe:2.3:a:linuxfoundation:nats-server:*:*:*:*:*:*:*:*
nats jwt_library < 2.0.1 cpe:2.3:a:nats:jwt_library:*:*:*:*:*:*:*:*

References for CVE-2021-3127

URL Tags
https://advisories.nats.io/CVE/CVE-2021-3127.txt Exploit Vendor Advisory
cvelogic Threat Intelligence