CVE-2020-5135: SonicWall SonicOS Buffer Overflow Vulnerability

Is it exploited?

Yes. CISA added it to the Known Exploited Vulnerabilities catalog on 15 Mar 2022, 519 days after the CVE record was published.

How likely is exploitation in the next 30 days?

26.9%

EPSS score, percentile 98 of all scored records

How severe?

9.8 Critical

CVSS v3.1 base score, from CISA's enrichment of the record

What should I do?

Required action (CISA), due 5 Apr 2022: Apply updates per vendor instructions.

The CVE record links no vendor advisory, patch or mitigation.

Which versions are affected?

Affected: SonicOS 6.5.4.7-79n and earlier; SonicOS 6.5.1.11-4n and earlier; SonicOS 6.0.5.3-93o and earlier; SonicOSv 6.5.4.4-44v-21-794 and earlier; SonicOS 7.0.0.0-1

Versions by product

Source: CISA Known Exploited Vulnerabilities (KEV) catalog, 2026.10.28, as of 28 Oct 2026; FIRST Exploit Prediction Scoring System (EPSS), v2026.06.15, as of 28 Oct 2026; CVE List V5 (CVE Program), cve_2026-10-28_0000Z, as of 28 Oct 2026. About the data.

What to do

CISA due date for this action: 5 April 2022.

Advisories and patches

The CVE record links no vendor advisory, patch or mitigation.

Linked from CISA's catalog entry

• https://nvd.nist.gov/vuln/detail/CVE-2020-5135

Affected products and versions

As listed in the CVE record.

Source: CVE List V5 (CVE Program), cve_2026-10-28_0000Z, as of 28 Oct 2026. About the data.

About this vulnerability

A buffer overflow vulnerability in SonicOS allows a remote attacker to cause Denial of Service (DoS) and potentially execute arbitrary code by sending a malicious request to the firewall.

Summary: CISA's KEV catalog, as of 28 Oct 2026.

• CISA added CVE-2020-5135 to its Known Exploited Vulnerabilities (KEV) catalog on 15 Mar 2022.
• CISA marks it as known to be used in ransomware campaigns.
• The due date CISA sets for the required action is 5 Apr 2022.
• The CVE record was published on 12 Oct 2020, 519 days before it was added to KEV.
• The CVE record carries a CVSS v3.1 base score of 9.8 (Critical), taken from CISA's enrichment of the record.
• FIRST's EPSS model puts the probability of exploitation in the next 30 days at 26.9% (percentile 98), as of 28 Oct 2026.
• CISA's SSVC assessment in the CVE record: exploitation active, automatable yes, technical impact total.

Source: CISA Known Exploited Vulnerabilities (KEV) catalog, 2026.10.28, as of 28 Oct 2026; CVE List V5 (CVE Program), cve_2026-10-28_0000Z, as of 28 Oct 2026; FIRST Exploit Prediction Scoring System (EPSS), v2026.06.15, as of 28 Oct 2026. About the data.

Description

A buffer overflow vulnerability in SonicOS allows a remote attacker to cause Denial of Service (DoS) and potentially execute arbitrary code by sending a malicious request to the firewall. This vulnerability affected SonicOS Gen 6 version 6.5.4.7, 6.5.1.12, 6.0.5.3, SonicOSv 6.5.4.v and Gen 7 version 7.0.0.0.

Source: CVE List V5 (CVE Program), cve_2026-10-28_0000Z, as of 28 Oct 2026. About the data.

Weakness

• CWE-120: Buffer Copy without Checking Size of Input

CWE and CAPEC are maintained by MITRE; the entries are those named in the CVE record and the KEV entry.

Timeline

References

• psirt.global.sonicwall.com

More exploited SonicWall vulnerabilities

• CVE-2026-83548: SonicWall SMA1000 Appliances Server-Side Request Forgery Vulnerability (added 2 Sep 2026)
• CVE-2026-83549: SonicWall SMA1000 Appliances OS Command Injection Vulnerability (added 2 Sep 2026)
• CVE-2026-15409: SonicWall SMA1000 Appliances Server-Side Request Forgery Vulnerability (added 14 Jul 2026)
• CVE-2026-15410: SonicWall SMA1000 Appliances Code Injection Vulnerability (added 14 Jul 2026)
• CVE-2025-40602: SonicWall SMA1000 Missing Authorization Vulnerability (added 17 Dec 2025)
• CVE-2023-44221: SonicWall SMA100 Appliances OS Command Injection Vulnerability (added 1 May 2025)