SonicWall SonicOS Buffer Overflow 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.
- Vendor
- SonicWall
- Product
- SonicOS
- CVSS
- 9.8
- EPSS (exploit probability)
- 26.9%
- Status
- kevransomware use
- CISA patch-by (BOD 22-01)
- Added to KEV
Is CVE-2020-5135 being exploited?
Yes. CISA added CVE-2020-5135 to its Known Exploited Vulnerabilities catalog on . CISA only lists a CVE when it has reliable evidence of exploitation in the wild. CISA marks it as known to be used in ransomware campaigns.
FIRST's EPSS model puts the probability of exploitation activity in the next 30 days at 26.9% (scored October 14, 2026).
- CISA KEV[ LISTED ]
- ENISA EUVD (exploited)[ — ]
- CIRCL KEV[ — ]
Catalog snapshot 2026-10-21. Full cross-catalog view: /kev-comparison
What to do
CISA required actionApply updates per vendor instructions.
US federal civilian agencies must remediate by (21 days after listing) under BOD 22-01. Everyone else: that deadline is a sensible upper bound, not a target. Vendor guidance and the NVD record are linked under Source above.
Other SonicWall SonicOS CVEs we track
| CVE / Vulnerability | Severity | CVSS | EPSS | Added to KEV |
|---|---|---|---|---|
| CVE-2024-53704 SonicWall SonicOS SSLVPN Improper Authentication Vulnerabilityransomware use | [ CRITICAL ] | 9.8 | 95.3% | |
| CVE-2024-40766 SonicWall SonicOS Improper Access Control Vulnerabilityransomware use | [ CRITICAL ] | 9.8 | 18.4% |