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Sonicos CVE-2026-0400

MEDIUM
Use of Externally-Controlled Format String (CWE-134)
2026-02-24 PSIRT@sonicwall.com
4.9
CVSS 3.1 · NVD
View

Vulnerability Assessment

Weakness
CWE
OWASP Top 10:2025
A05:2025 - Injection
ASVS 5.0
V1 - Encoding and Sanitization Format string safety
Impact

CVSS 4.9 (MEDIUM). Attack vector: Network. Complexity: Low. Privileges required: High. User interaction: None. Exploitable via remote/network.

Exploit ScenarioDerived

A remote attacker could exploit this vulnerability to compromise the affected system.

This Month Plan within 30 days. Why: MEDIUM severity (CVSS 4.0-6.9).
No patch listed yet 0.2% exploitation probability (EPSS)

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AnalysisAIv1 – Mar 12, 2026

SonicOS firewalls are vulnerable to a post-authentication format string vulnerability that permits authenticated remote attackers to trigger a denial of service condition and crash the affected device. The attack requires valid credentials but can be executed over the network without user interaction. No patch is currently available for this vulnerability.

Earlier versions of this analysis (1)
v1 Mar 12, 2026 - 21:55 CVSS 4.9

A post-authentication Format String vulnerability in SonicOS allows a remote attacker to crash a firewall. [CVSS 4.9 MEDIUM]

RemediationAI

Monitor vendor advisories for a patch. Restrict network access to the affected service where possible.

Affects your stack

Find out whether the stacks and servers you run are on an affected version.

Checking this CVE against your own stacks and servers is part of the Basic plan and up.

Technical ContextAI · show details

Classified as CWE-134 (Use of Externally-Controlled Format String). Affects Sonicos. A post-authentication Format String vulnerability in SonicOS allows a remote attacker to crash a firewall.

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  • Exploit and PoC references, threat intelligence from 22 sources

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Severity by source

NVD PRIMARY 4.9 MEDIUM
AV:N/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H

Primary rating from NVD · only source for this CVE.

CVSS VectorNVD

Attack Vector
Network
Attack Complexity
Low
Privileges Required
High
User Interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

DescriptionCVE.org

A post-authentication Format String vulnerability in SonicOS allows a remote attacker to crash a firewall.

Executive ViewAI

Why It Matters

Organizations using A post-authentication Format String vulnerability in SonicOS should be aware of moderate risk from CVE-2026-0400 rated CVSS 4.9. Exploitation could compromise the security of affected deployments. Organizations should apply vendor updates when available and monitor for exploitation.

Business Impact: Low
Compensating Controls

Apply vendor patch. If patching is delayed: restrict network access and enable monitoring.

Threat Intelligence Overview

EPSS Score
0.2%
Top 60% exploitable
Data Quality
3 sources
Confidence: Low

How this decision was reached

The engine reads each signal below and applies a fixed list of rules from top to bottom. The first rule that matches sets the recommended action – like a statement, every line is shown.

SignalValue
Severity MEDIUM
CISA KEV No
Public POC No
EPSS 0.2%
Patch available No
Active threat No
Deciding rule
MEDIUM severity (CVSS 4.0-6.9)
What every action level means
Emergency Immediate action required. Criteria: CRITICAL + in CISA KEV (actively exploited) without patch, OR CRITICAL + EPSS > 30% without patch, OR CRITICAL + active threat signals without patch.
Act Now Prioritize within 24-48h. Criteria: in KEV with patch available, OR CRITICAL + public POC, OR HIGH + EPSS > 10%, OR CRITICAL + active threat, OR any CRITICAL severity.
This Week Schedule remediation this week. Criteria: HIGH severity (CVSS 7.0-8.9). Patch within normal change window.
This Month Plan within 30 days. Criteria: MEDIUM severity (CVSS 4.0-6.9), lower exploitation probability. Include in regular patch cycle.
Monitor Track and reassess. Criteria: LOW severity (CVSS 0.1-3.9), minimal exploitation risk. No immediate action needed.

SSVC AssessmentENISA

SSVC Decision· derived
Defer
Exploitation· derived
None
System Exposure· derived
Open
Automatable· derived
No
Human Impact
Low

Priority Score

24
Low Medium High Critical
KEV: 0
EPSS: 0
CVSS: +24
PoC: 0
Weaponized: 0
Threat intel: 0
Gov advisory: 0

Attack Technique

Denial of Service attacks render applications or systems unavailable by overwhelming resources or triggering failure conditions.

Affected Products (CPE)CVE.org

cpe:2.3:o:sonicwall:sonicos:*:*:*:*:*:*:*:*
cpe:2.3:o:sonicwall:sonicos:*:*:*:*:*:*:*:*
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An improper access control vulnerability has been identified in the SonicWall SonicOS management access, potentially lea

CVE-2021-3449 MEDIUM
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An OpenSSL TLS server may crash if sent a maliciously crafted renegotiation ClientHello message from a client. Rated med

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CVE-2019-12258 HIGH POC
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Wind River VxWorks 6.6 through vx7 has Session Fixation in the TCP component. Rated high severity (CVSS 7.5), this vulne

CVE-2021-3450 HIGH
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The X509_V_FLAG_X509_STRICT flag enables additional security checks of the certificates present in a certificate chain.

CVE-2021-20031 MEDIUM POC
6.1 Oct 12

A Host Header Redirection vulnerability in SonicOS potentially allows a remote attacker to redirect firewall management

CVE-2024-22394 CRITICAL
9.8 Feb 08

An improper authentication vulnerability has been identified in SonicWall SonicOS SSL-VPN feature, which in specific con

CVE-2022-22274 CRITICAL POC
9.8 Mar 25

A Stack-based buffer overflow vulnerability in the SonicOS via HTTP request allows a remote unauthenticated attacker to

CVE-2020-5135 CRITICAL
9.8 Oct 12

A buffer overflow vulnerability in SonicOS allows a remote attacker to cause Denial of Service (DoS) and potentially exe

CVE-2019-12261 CRITICAL
9.8 Aug 09

Wind River VxWorks 6.7 though 6.9 and vx7 has a Buffer Overflow in the TCP component (issue 3 of 4). Rated critical seve

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