SonicOS firewalls
CVE-2021-20027: Buffer overflow in SonicOS
A buffer overflow vulnerability in SonicOS allows a remote attacker to cause a Denial of Service (DoS) by sending a specially crafted request.
Published
ExploitedNot in CISA KEV
Ransomware useNot reportedPer CISA
SeverityUnknown
EPSS1.3%Chance of exploitation in 30 days
Public exploitNot tracked
FixSee advisory
Automatic summary from the vendor's CVE record. We haven't written a full analysis of this vulnerability yet.
Affected and fixed versions
| Product / branch | Fixed in |
|---|---|
| SonicOS SonicOS 5.9 | See the advisory |
| SonicOS SonicOSv 6.5 | See the advisory |
| SonicOS SonicOS 6.0 | See the advisory |
| SonicOS SonicOS 6.5 | See the advisory |
| SonicOS SonicOS 7.0 | See the advisory |
Always confirm against the vendor advisory, which lists every fixed hotfix.
What it is
A buffer overflow vulnerability in SonicOS allows a remote attacker to cause a Denial of Service (DoS) by sending a specially crafted request. This vulnerability affects SonicOS Gen5, Gen6, Gen7 platforms, and SonicOSv virtual firewalls.
Sources
KEV status, EPSS score and vendor data refreshed automatically, last on 13 Oct 2026.