Threats / SonicWall / CVE-2020-5135
CVE-2020-5135
· EUVD no mirror located
· GCVE no mirror located
Verified 2026-06-22
SonicWall SonicOS vulnerability
A buffer overflow in SonicOS allows remote attackers to cause denial of service and potentially execute arbitrary code on affected firewalls.
Verdict
Today item — known-exploited.
Remote attackers can exploit this buffer overflow vulnerability without authentication to disrupt firewall availability or gain code execution, posing significant risk to network perimeter security.
01
Is it exploitable?
— the evidence, ranked above the scoreReported exploitation
7 independent public reports of in-the-wild exploitation are cataloged.Distinct reporting sources (vendor, incident response, government); open them for the underlying claims.
Exploited in the wild
Listed in the CISA Known Exploited Vulnerabilities catalog (added 2022-03-15).
Probability (EPSS)
EPSS 0.26869 — modeled likelihood of exploitation activity.EPSS is a daily-changing model output — open the source for today's value.
Severity / affected
Affected: SonicWall, SonicOS. Confirm exact fixed builds in the vendor advisory.
Weakness (CWE)
Mapped to CWE-120 Buffer Copy without Size Check — weakness family: Memory safety.CWE assignment from the public NVD record; the weakness class drives how the flaw is exploited.
02
Who’s exploiting it?
— attribution turns risk into urgencyAttribution not established
No confirmed (advisory-backed) threat-actor attribution is established for this record. Absence of a named actor is not absence of compromise — see Coverage & confidence.
03
Why it matters
— the attack path, told twice: adversary, then board1
Front door — unauthenticated access narrative 1
Attacker
I craft a malicious request designed to overflow a buffer in the SonicOS network stack.
Business
Firewall availability is disrupted, blocking legitimate traffic and exposing the network perimeter.
2
Keys to the kingdom — privilege/identity takeover narrative 2
Attacker
I send the payload to the firewall's exposed network interface without requiring credentials.
Business
The attack bypasses authentication controls, allowing unauthenticated remote exploitation.
3
Lateral reach — past segmentation narrative 3
Attacker
I achieve arbitrary code execution on the compromised firewall device.
Business
The attacker gains control of critical network infrastructure, enabling lateral movement and data exfiltration.
04
What to do
— defensible action- Remediate per the vendor advisory — confirm the fixed build for your version and verify exposure.1
Say it to the boardA vulnerability with this evidence profile is a defensible budget line, not a backlog ticket — fund the change against the proof above.
05