CVE-2024-40766
CVE-2024-40766 is a security flaw in SonicWall SonicOS, SonicWall’s firewall and remote-access equipment. Attackers can reach parts of SonicWall SonicOS that should be locked to them. The US Cybersecurity and Infrastructure Security Agency (CISA) added it to its catalog of flaws known to be used in attacks on 9 Sep 2024, and says ransomware gangs have used it.[1]
SonicWall SonicOS is business software or equipment. Most families won’t have it, but attackers break into it to get inside companies, and from there to what those companies hold about their customers, patients and staff. SonicWall has published a fix or advice.
Description
CISA calls it an improper access control in SonicWall SonicOS. In its words: “SonicWall SonicOS contains an improper access control vulnerability that could lead to unauthorized resource access and, under certain conditions, may cause the firewall to crash.”[1]
The CVE record adds: “An improper access control vulnerability has been identified in the SonicWall SonicOS management access, potentially leading to unauthorized resource access and in specific conditions, causing the firewall to crash. This issue affects SonicWall Firewall Gen 5 and Gen 6 devices, as well as Gen 7 devices running SonicOS 7.0.1-5035 and older versions.”[2]
The underlying weakness is improper access control (CWE-284), in MITRE’s list of common software weaknesses.
It scores 9.8 out of 10 on the Common Vulnerability Scoring System, which rates it critical, scored by NVD using CVSS 3.1.[2]
Affected versions
NVD’s record doesn’t list version ranges for it; SonicWall’s advisory has them[3]. CISA names the product as SonicWall SonicOS.
Most families won’t have SonicWall SonicOS; it’s for whoever looks after IT at work.
Exploitation
CISA added it to its catalog of known exploited vulnerabilities on 9 Sep 2024, 17 days after it was made public. CISA lists a flaw only when it has reliable evidence of it being exploited, and gave US federal agencies until 30 Sep 2024 to fix it.[1] CISA says ransomware gangs have used it.
FIRST’s Exploit Prediction Scoring System, which estimates how likely a flaw is to be used in attacks in the next 30 days from what it sees across the internet, puts it at 18%. That’s in the top 3% of the flaws it scores.[4]
CISA assesses it as automatable: attackers can run it against many targets at once.
CISA doesn’t say who was attacked, or how.
Fix
SonicWall has published a fix or advice.[3] CISA’s required action: “Apply mitigations per vendor instructions or discontinue use of the product if mitigations are unavailable.”[1]
- Check whether you use it.SonicWall SonicOS is business software or equipment, so most families won’t have it. If you run a business, or work from home on company equipment, ask whoever looks after your IT.
- Send this page to your IT person.Ask them to confirm it’s fixed, or not in use. CISA gave US government agencies until 30 Sep 2024 to fix it.
- If it can’t be fixed, take it offline.CISA’s advice when there’s no fix is to stop using the product, or take it off the internet, until there is one.
You can’t fix someone else’s server, but you can watch for what follows a break-in like this: a breach notice, a password reset you didn’t ask for, or a scam message that knows things it shouldn’t. HARD watches for those for you and your family.
Timeline
| Date | Event |
|---|---|
| The flaw is made public in the National Vulnerability Database, with a severity score of 9.8.[2] | |
| CISA adds it to its catalog of flaws known to be used in attacks, noting that ransomware gangs have used it.[1] | |
| CISA’s deadline for US government agencies to fix it.[1] | |
| FIRST puts the odds of it being used in attacks in the next 30 days at 18%.[4] |
See also
Other SonicWall SonicOS flaws
- CVE-2024-53704: SSLVPN improper authentication ·
- CVE-2020-5135: buffer overflow ·
Other SonicWall flaws
- CVE-2026-83549, SonicWall SMA1000 Appliances: OS command injection ·
- CVE-2026-83548, SonicWall SMA1000 Appliances: server-side request forgery ·
- CVE-2026-15410, SonicWall SMA1000 Appliances: code injection ·
- CVE-2026-15409, SonicWall SMA1000 Appliances: server-side request forgery ·
- CVE-2025-40602, SonicWall SMA1000 appliance: sMA1000 missing authorization ·
Other improper access control flaws
- CVE-2015-3306, ProFTPD: improper access control ·
- CVE-2026-21962, Oracle HTTP Server and Oracle Weblogic Server Proxy Plug-in: improper access control ·
- CVE-2026-56290, Joomlack Page Builder: improper access control ·
- CVE-2026-34908, Ubiquiti UniFi OS: improper access control ·
- CVE-2026-48907, Widget Factory Joomla Content Editor: improper access control ·
Added the same day
- CVE-2017-1000253, Linux Kernel: PIE stack buffer corruption ·
- CVE-2016-3714, ImageMagick: improper input validation ·
Every SonicWall flaw on CISA’s list · Everything added in September 2024
References
- ^ Cybersecurity and Infrastructure Security Agency. “SonicWall SonicOS Improper Access Control Vulnerability”. Known Exploited Vulnerabilities Catalog, added 9 Sep 2024.
- ^ National Institute of Standards and Technology. “CVE-2024-40766 Detail”. National Vulnerability Database, published 23 Aug 2024.
- ^ SonicWall. Advisories and fixes: psirt.global.sonicwall.com, sonicwall.com.
- ^ FIRST. “Exploit Prediction Scoring System”. EPSS 0.184, percentile 97.2, 31 Oct 2026.
- CVE Program. “CVE-2024-40766”. The official CVE record.
This article is built from CISA’s catalog (version 2026.10.30), NVD’s record and FIRST’s scores, kept in HARD’s database and checked every morning. The plain English is HARD’s.