How severe is CVE-2021-34728?

CVE-2021-34728 has a CVSS 3.x base score of 7.8, rated high severity. It is exploitable over local access with low attack complexity, requires low privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.

Is CVE-2021-34728 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (22nd percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-34728?

CVE-2021-34728 affects Cisco Ios Xr. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2021-34728?

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-2021-34728 published?

CVE-2021-34728 was published on 2021-09-09 and last updated on 2026-06-17.

CVE-2021-34728

CVE-2021-34728 is a high-severity vulnerability in Cisco Ios Xr with a CVSS 3.x base score of 7.8. 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-78.

Key facts

Severity: High (CVSS 3.x base score 7.8)
CVSS v2: 7.2
EPSS exploit prediction: 0% (22nd percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-78
Affected product: Cisco Ios Xr
Published: 2021-09-09
Last modified: 2026-06-17

Description

Multiple vulnerabilities in the CLI of Cisco IOS XR Software could allow an authenticated, local attacker with a low-privileged account to elevate privileges on an affected device. For more information about these vulnerabilities, see the Details section of this advisory.

Frequently asked questions

What is CVE-2021-34728?: Multiple vulnerabilities in the CLI of Cisco IOS XR Software could allow an authenticated, local attacker with a low-privileged account to elevate privileges on an affected device. For more information about these vulnerabilities, see the Details section of this advisory.
How severe is CVE-2021-34728?: CVE-2021-34728 has a CVSS 3.x base score of 7.8, rated high severity. It is exploitable over local access with low attack complexity, requires low privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.
Is CVE-2021-34728 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (22nd percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-34728?: CVE-2021-34728 affects Cisco Ios Xr. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2021-34728?: 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-2021-34728 published?: CVE-2021-34728 was published on 2021-09-09 and last updated on 2026-06-17.

References

https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-iosxr-privescal-dZYMrKf

Affected products (1)

cpe:2.3:o:cisco:ios_xr:*:*:*:*:*:*:*:*

More vulnerabilities in Cisco Ios Xr

CVE-2020-3284 — Critical (CVSS 9.8): A vulnerability in the enhanced Preboot eXecution Environment (PXE) boot loader for Cisco IOS XR 64-bit Software could…
CVE-2019-1710 — Critical (CVSS 9.8): A vulnerability in the sysadmin virtual machine (VM) on Cisco ASR 9000 Series Aggregation Services Routers running…
CVE-2025-20363 — Critical (CVSS 9.0): A vulnerability in the web services of Cisco Secure Firewall Adaptive Security Appliance (ASA) Software, Cisco Secure…
CVE-2026-20046 — High (CVSS 8.8): A vulnerability in task group assignment for a specific CLI command in Cisco IOS XR Software could allow an…
CVE-2026-20040 — High (CVSS 8.8): A vulnerability in the CLI of Cisco IOS XR Software could allow an authenticated, local attacker to execute arbitrary…
CVE-2025-20138 — High (CVSS 8.8): A vulnerability in the CLI of Cisco IOS XR Software could allow an authenticated, local attacker to execute arbitrary…

All CVEs affecting Cisco Ios Xr →

Other CWE-78 (OS Command Injection) vulnerabilities

CVE-2026-56004 — Critical (CVSS 10.0): A shellcode injection in the mercurial handler of the obs tar_scm source service before version 0.12.4 could be used by…
CVE-2026-56415 — Critical (CVSS 10.0): Storage Concentrator (SC & SCVM) contains a command injection vulnerability within the debug.pl script that is…
CVE-2026-56413 — Critical (CVSS 10.0): Storage Concentrator (SC & SCVM) contains a command injection vulnerability in the ms_service.pl service, which listens…
CVE-2026-49869 — Critical (CVSS 10.0): Kestra is an open-source, event-driven orchestration platform. Prior to 1.0.45 and 1.3.21, AuthenticationFilter in…
CVE-2026-49261 — Critical (CVSS 10.0): MariaDB server is a community developed fork of MySQL server. Versions 10.6.1 through 10.6.26, 10.11.1 through…
CVE-2026-10520 — Critical (CVSS 10.0): An OS Command Injection vulnerability in Ivanti Sentry before the R10.5.2, R10.6.2 and R10.7.1 versions allows a…

Browse all CWE-78 (OS Command Injection) vulnerabilities →