No exploitation reportedFix available

CVE-2021-1539

Q: Is CVE-2021-1539 actively exploited?

Active exploitation of CVE-2021-1539 has not been confirmed. Its EPSS score was 1.1% on 2026-10-22, the estimated probability of exploitation in the next 30 days.

Q: What is the CVSS score for CVE-2021-1539?

CVE-2021-1539 has a CVSS v3 base score of 8.8 (HIGH severity), with vector string CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H.

No exploitation reported by the sources we read.

Published2021-06-04
Fixed in21.20.8 · 21.19.11 · 21.19.n7 · 21.18.16 · 21.17.10 · 21.16.9
WeaknessCWE-863

Am I affected?

With a domain, we read the version its public headers and pages expose. A distribution build can carry the fix under an older number.

Description

Multiple vulnerabilities in the authorization process of Cisco ASR 5000 Series Software (StarOS) could allow an authenticated, remote attacker to bypass authorization and execute a subset of CLI commands on an affected device. For more information about these vulnerabilities, see the Details section of this advisory.

Timeline

dates in UTC

2021-06-0417:15CVE publishedNVD

Observed activity

isMalicious corpus · updated 2026-10-23 21:37 UTC

Indicators tagged with this CVE, per day0 indicators over 7 days

Block these indicators

Firewall list (EDL, text): https://api.ismalicious.com/edl/cve/CVE-2021-1539?format=txt
CSV export: https://api.ismalicious.com/edl/cve/CVE-2021-1539?format=csv
TAXII collection of exploited CVEs
The EDL and CSV take an API key on the Pro plan.

Versions per branch

NVD

Cisco starosversion to verify

Branch	Affected	Fixed in	Source
21.20	≥ 21.20.0, < 21.20.8	21.20.8	NVD
21.19	≥ 21.19.0, < 21.19.11	21.19.11	NVD
21.19	≥ 21.19.n, < 21.19.n7	21.19.n7	NVD
21.18	≥ 21.18.0, < 21.18.16	21.18.16	NVD
21.17	≥ 21.17.0, < 21.17.10	21.17.10	NVD
21.16	< 21.16.9	21.16.9	NVD

Cisco virtualized packet core

Branch	Affected	Fixed in	Source
—	all versions	no fix published	NVD

as publishedRanges as NVD and OSV publish them; a distribution’s build can be fixed under an older number.

Fix

Update Cisco staros to 21.20.8 · 21.19.11 · 21.19.n7 · 21.18.16 · 21.17.10 · 21.16.9

Advisories and patches

tools.cisco.comVendor Advisory

Detection

Nuclei template: none so far
Exploit-DB: no entry
Proof-of-concept repositories: none listed

Sources

CISA-ADPSSVC decisionnone2024-11-07
OpenCVESSVC decisionnone—
CNACVSS 3.18.1read 2026-10-23
NVDCVSS 3.18.8read 2026-10-23
NVDCVSS 2.06.5read 2026-10-23
CNAweakness (CWE)CWE-863read 2026-10-23
FIRST EPSSEPSS score1.1 %2026-10-22

Technical details

CVSS v3 Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Published: 2021-06-04
Last Modified: 2026-06-17
NVD status: Modified

Frequently asked questions

What is CVE-2021-1539?

Is CVE-2021-1539 actively exploited?

Active exploitation of CVE-2021-1539 has not been confirmed. Its EPSS score was 1.1% on 2026-10-22, the estimated probability of exploitation in the next 30 days.

What is the CVSS score for CVE-2021-1539?

CVE-2021-1539 has a CVSS v3 base score of 8.8 (HIGH severity), with vector string CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H.

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