How severe is CVE-2021-1539?

CVE-2021-1539 has a CVSS 3.x base score of 8.1, rated high severity. It is exploitable over network with low attack complexity, requires low privileges and no user interaction. Impact on confidentiality is high, integrity none, and availability high.

Is CVE-2021-1539 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (61st percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-1539?

CVE-2021-1539 primarily affects Cisco Staros. In total, 2 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2021-1539?

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-2021-1539 published?

CVE-2021-1539 was published on 2021-06-04 and last updated on 2026-06-17.

CVE-2021-1539

CVE-2021-1539 is a high-severity vulnerability in Cisco Staros with a CVSS 3.x base score of 8.1. 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-863.

Key facts

Severity: High (CVSS 3.x base score 8.1)
CVSS v2: 6.5
EPSS exploit prediction: 1% (61st percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-863
Affected product: Cisco Staros
Published: 2021-06-04
Last modified: 2026-06-17

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.

Frequently asked questions

What is CVE-2021-1539?: 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.
How severe is CVE-2021-1539?: CVE-2021-1539 has a CVSS 3.x base score of 8.1, rated high severity. It is exploitable over network with low attack complexity, requires low privileges and no user interaction. Impact on confidentiality is high, integrity none, and availability high.
Is CVE-2021-1539 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (61st percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-1539?: CVE-2021-1539 primarily affects Cisco Staros. In total, 2 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2021-1539?: 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-2021-1539 published?: CVE-2021-1539 was published on 2021-06-04 and last updated on 2026-06-17.

References

https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-asr5k-autho-bypass-mJDF5S7n

Affected products (2)

cpe:2.3:o:cisco:staros:*:*:*:*:*:*:*:*
cpe:2.3:a:cisco:virtualized_packet_core:-:*:*:*:*:*:*:*

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