SonicWall SonicOS Buffer Overflow Vulnerability
CVE-2020-5135 is a security vulnerability in SonicWall SonicOS, added to CISA KEV on March 15, 2022. Patch priority: Patch this week.
What it is
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.
Who's affected
Affects anyone whose network is fronted by a SonicWall firewall or SSL VPN. The device sits at the edge between your office and the internet and authenticates remote workers — exploitation typically means an attacker reaches inside without needing a user credential.
What to do
Apply updates per vendor instructions.
If you don't have someone in-house to verify the patch deployed across every endpoint — or you're not sure whether you're affected — that's exactly the kind of triage we do. Book a free 20-minute triage call.
Insurance readiness
Your insurer will ask if this is patched.
Unpatched entries on CISA's Known Exploited Vulnerabilities list are exactly what cyber-insurance carrier questionnaires probe for, and knowing which controls they check is how you keep a renewal from stalling.
Get the free carrier questionnaire →Severity
CVSS base score: 9.8 — CRITICAL
Weakness classification: CWE-120
CISA due date
Federal deadline: April 5, 2022. Federal agencies must complete the required action by this date. For private SMBs the deadline is advisory — but treat it as a strong recommendation, especially if you handle regulated data (HIPAA, GLBA, ABA model rules).
EPSS
EPSS score: 24.6% — higher than 98% of all scored CVEs.
EPSS estimates the probability of exploitation activity in the next 30 days. Every entry on this site is already confirmed exploited, so read it as relative urgency among the things you still have open, not as permission to wait.
Other exploited SonicWall SonicOS entries
More CISA KEV entries for SonicWall SonicOS. Same product line, same actively-exploited status.
Source
This entry comes from CISA's Known Exploited Vulnerabilities catalog, public US-Government data we pull daily. The plain-language framing and the what-to-do guidance above are ours. View the original entry on cisa.gov.