Threats / SonicWall / CVE-2020-5135
CVE-2020-5135
· EUVD no mirror located
· GCVE no mirror located
Verified 2026-08-04
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.
CISA KEV Yes · 2022-03-155EPSS 0.24563 (verify live)6CVSS 9.8 (CISA)4CISA SSVC Exploitation: active · Automatable: yes · Impact: total4
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 0.24563 — modeled likelihood of exploitation activity.EPSS is a daily-changing model output — open the source for today's value.
Severity / affected
CVSS 9.8 (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H) · Affected: SonicWall, SonicOS. Confirm exact fixed builds in the vendor advisory.CVSS — CISA-assigned via the ADP container (CVE.org), version 3.1; the CNA left no metrics, so CISA's own score is used ahead of NVD.
Weakness (CWE)
Mapped to CWE-120 Buffer Copy without Size Check — weakness family: Memory safety.CWE — CNA-assigned (CVE.org); the weakness class drives how the flaw is exploited.
CISA SSVC (triage disposition)
Exploitation: active · Automatable: yes · Technical Impact: totalCISA's own stakeholder-specific triage inputs, published in the CVE record (CISA Coordinator role). NOTE: this is CISA's three decision points; the final Act/Attend/Track decision also requires a Mission & Well-being input not published here, so no overall decision is asserted.
Currency of the record
CISA added this to its KEV catalog 519 days after the CVE record was published.KEV lag = CISA-KEV dateAdded − CVE.org datePublished; a floor on how long the known-exploited flaw sat in the public record before the federal catalog listed it. Severity/weakness here is CNA- or CISA-assigned (current at disclosure), independent of NVD's analysis backlog.
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