How severe is CVE-2021-33907?

CVE-2021-33907 has a CVSS 3.x base score of 9.8, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.

Is CVE-2021-33907 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 3% (86th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-33907?

CVE-2021-33907 affects Zoom Meetings. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2021-33907?

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

When was CVE-2021-33907 published?

CVE-2021-33907 was published on 2021-09-27 and last updated on 2026-06-17.

CVE-2021-33907

CVE-2021-33907 is a critical-severity vulnerability in Zoom Meetings with a CVSS 3.x base score of 9.8. 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-295.

Key facts

Severity: Critical (CVSS 3.x base score 9.8)
CVSS v2: 10.0
EPSS exploit prediction: 3% (86th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-295
Affected product: Zoom Meetings
Published: 2021-09-27
Last modified: 2026-06-17

Description

The Zoom Client for Meetings for Windows in all versions before 5.3.0 fails to properly validate the certificate information used to sign .msi files when performing an update of the client. This could lead to remote code execution in an elevated privileged context.

Frequently asked questions

What is CVE-2021-33907?: The Zoom Client for Meetings for Windows in all versions before 5.3.0 fails to properly validate the certificate information used to sign .msi files when performing an update of the client. This could lead to remote code execution in an elevated privileged context.
How severe is CVE-2021-33907?: CVE-2021-33907 has a CVSS 3.x base score of 9.8, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.
Is CVE-2021-33907 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 3% (86th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-33907?: CVE-2021-33907 affects Zoom Meetings. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2021-33907?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.
When was CVE-2021-33907 published?: CVE-2021-33907 was published on 2021-09-27 and last updated on 2026-06-17.

References

https://explore.zoom.us/en/trust/security/security-bulletin/

Affected products (1)

cpe:2.3:a:zoom:meetings:*:*:*:*:*:windows:*:*

More vulnerabilities in Zoom Meetings

CVE-2021-34423 — Critical (CVSS 9.8): A buffer overflow vulnerability was discovered in Zoom Client for Meetings (for Android, iOS, Linux, macOS, and…
CVE-2022-28768 — High (CVSS 8.8): The Zoom Client for Meetings Installer for macOS (Standard and for IT Admin) before version 5.12.6 contains a local…
CVE-2022-28763 — High (CVSS 8.8): The Zoom Client for Meetings (for Android, iOS, Linux, macOS, and Windows) before version 5.12.2 is susceptible to a…
CVE-2022-28757 — High (CVSS 8.8): The Zoom Client for Meetings for macOS (Standard and for IT Admin) starting with version 5.7.3 and before 5.11.6…
CVE-2022-28751 — High (CVSS 8.8): The Zoom Client for Meetings for MacOS (Standard and for IT Admin) before version 5.11.3 contains a vulnerability in…
CVE-2022-28756 — High (CVSS 8.8): The Zoom Client for Meetings for macOS (Standard and for IT Admin) starting with version 5.7.3 and before 5.11.5…

All CVEs affecting Zoom Meetings →

Other CWE-295 (Improper Certificate Validation) vulnerabilities

CVE-2026-4370 — Critical (CVSS 10.0): A vulnerability was identified in Juju from version 3.2.0 until 3.6.19 and from version 4.0 until 4.0.4, where the…
CVE-2026-30836 — Critical (CVSS 10.0): Step CA is an online certificate authority for secure, automated certificate management for DevOps. Versions 0.30.0-rc6…
CVE-2025-68121 — Critical (CVSS 10.0): During session resumption in crypto/tls, if the underlying Config has its ClientCAs or RootCAs fields mutated between…
CVE-2022-20703 — Critical (CVSS 10.0): Multiple vulnerabilities in Cisco Small Business RV160, RV260, RV340, and RV345 Series Routers could allow an attacker…
CVE-2021-1471 — Critical (CVSS 9.9): Multiple vulnerabilities in Cisco Jabber for Windows, Cisco Jabber for MacOS, and Cisco Jabber for mobile platforms…
CVE-2026-20184 — Critical (CVSS 9.8): A vulnerability in the integration of single sign-on (SSO) with Control Hub in Cisco Webex Services could have allowed…

Browse all CWE-295 (Improper Certificate Validation) vulnerabilities →