How severe is CVE-2021-3127?

CVE-2021-3127 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity none, and availability none.

Is CVE-2021-3127 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (70th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-3127?

CVE-2021-3127 primarily affects Linuxfoundation Nats-server. In total, 2 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2021-3127?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.

When was CVE-2021-3127 published?

CVE-2021-3127 was published on 2021-03-16 and last updated on 2026-06-17.

CVE-2021-3127

CVE-2021-3127 is a high-severity vulnerability in Linuxfoundation Nats-server with a CVSS 3.x base score of 7.5. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-755.

Key facts

Severity: High (CVSS 3.x base score 7.5)
CVSS v2: 5.0
EPSS exploit prediction: 1% (70th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-755
Affected product: Linuxfoundation Nats-server
Published: 2021-03-16
Last modified: 2026-06-17

Description

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.

Frequently asked questions

What is CVE-2021-3127?: 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.
How severe is CVE-2021-3127?: CVE-2021-3127 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity none, and availability none.
Is CVE-2021-3127 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (70th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-3127?: CVE-2021-3127 primarily affects Linuxfoundation Nats-server. In total, 2 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2021-3127?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
When was CVE-2021-3127 published?: CVE-2021-3127 was published on 2021-03-16 and last updated on 2026-06-17.

References

https://advisories.nats.io/CVE/CVE-2021-3127.txt

Affected products (2)

cpe:2.3:a:linuxfoundation:nats-server:*:*:*:*:*:*:*:*
cpe:2.3:a:nats:jwt_library:*:*:*:*:*:*:*:*

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CVE-2021-42142 — Critical (CVSS 9.8): An issue was discovered in Contiki-NG tinyDTLS through master branch 53a0d97. DTLS servers mishandle the early use of a…
CVE-2021-42141 — Critical (CVSS 9.8): An issue was discovered in Contiki-NG tinyDTLS through 2018-08-30. One incorrect handshake could complete with…
CVE-2023-38406 — Critical (CVSS 9.8): bgpd/bgp_flowspec.c in FRRouting (FRR) before 8.4.3 mishandles an nlri length of zero, aka a "flowspec overflow."
CVE-2022-23121 — Critical (CVSS 9.8): This vulnerability allows remote attackers to execute arbitrary code on affected installations of Netatalk.…

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