CVE-2021-40120
CVE-2021-40120 is a medium-severity vulnerability in Cisco Ios Xr with a CVSS 3.x base score of 6.5. 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-78.
Key facts
- Severity: Medium (CVSS 3.x base score 6.5)
- CVSS v2: 9.0
- EPSS exploit prediction: 2% (78th percentile)
- Actively exploited: Not listed in CISA KEV
- Weakness: CWE-78
- Affected product: Cisco Ios Xr
- Published:
- Last modified:
Description
A vulnerability in the web-based management interface of certain Cisco Small Business RV Series Routers could allow an authenticated, remote attacker with administrative privileges to inject arbitrary commands into the underlying operating system and execute them using root-level privileges. This vulnerability is due to insufficient validation of user-supplied input. An attacker could exploit this vulnerability by sending malicious input to a specific field in the web-based management interface of an affected device. A successful exploit could allow the attacker to execute arbitrary commands on the underlying Linux operating system as a user with root-level privileges.
Frequently asked questions
- What is CVE-2021-40120?
- A vulnerability in the web-based management interface of certain Cisco Small Business RV Series Routers could allow an authenticated, remote attacker with administrative privileges to inject arbitrary commands into the underlying operating system and execute them using root-level privileges. This vulnerability is due to insufficient validation of user-supplied input. An attacker could exploit this vulnerability by sending malicious input to a specific field in the web-based management interface of an affected device. A successful exploit could allow the attacker to execute arbitrary commands on the underlying Linux operating system as a user with root-level privileges.
- How severe is CVE-2021-40120?
- CVE-2021-40120 has a CVSS 3.x base score of 6.5, rated medium severity. It is exploitable over network with low attack complexity, requires high privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability none.
- Is CVE-2021-40120 being actively exploited?
- It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 2% (78th percentile), an estimate of the probability of exploitation in the next 30 days.
- What products are affected by CVE-2021-40120?
- CVE-2021-40120 primarily affects Cisco Ios Xr. In total, 2 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
- How do I fix CVE-2021-40120?
- Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
- When was CVE-2021-40120 published?
- CVE-2021-40120 was published on 2021-11-04 and last updated on 2026-06-17.
References
Affected products (2)
- cpe:2.3:o:cisco:ios_xr:4.2.3.06:*:*:*:*:*:*:*
- cpe:2.3:a:cisco:application_extension_platform:1.5.1.13:*:*:*:*:*:*:*
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-2026-19188 — Critical (CVSS 10.0): A critical OS command injection vulnerability has been identified in the Haiwell IoT Cloud HMI Gateway product. The…
- CVE-2026-48362 — Critical (CVSS 10.0): ColdFusion is affected by an Improper Neutralization of Special Elements used in an OS Command ('OS Command Injection')…
- CVE-2026-16812 — Critical (CVSS 10.0): VeloCloud Orchestrator (VCO) on-prem has a security issue where this issue may allow a remote attacker to access…
- CVE-2026-6516 — Critical (CVSS 10.0): Zohocorp ManageEngine ADAudit Plus versions before 8606 are affected by Unauthenticated Remote code execution due to…
- CVE-2026-46339 — Critical (CVSS 10.0): 9Router is an AI router & token saver. From 0.4.30 until 0.4.37, 9Router's src/proxy.js middleware did not protect…
- CVE-2026-59726 — Critical (CVSS 10.0): Ruflo is an agent meta-harness for Claude Code and Codex. Prior to 3.16.3, ruflo's default docker-compose deployment…