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Known exploited · SonicWall

CVE-2021-20023: SonicWall Email Security Path Traversal Vulnerability

What it is

SonicWall Email Security contains a path traversal vulnerability that allows a post-authenticated attacker to read files on the remote host. This vulnerability has known usage in a SonicWall Email Security exploit chain along with CVE-2021-20021 and CVE-2021-20022 to achieve privilege escalation.

Added November 3, 2021Due November 17, 2021CISA KEV catalog 2026.10.01

Vendor
SonicWall
Product
SonicWall Email Security
Added to KEV
November 3, 2021
CISA due date
November 17, 2021
Ransomware use
Known

What CISA requires

Apply updates per vendor instructions.

Forensic triage

No

What to do now

  1. Find every instance of SonicWall Email Security you run, including the forgotten ones, and check its version against the vendor advisory.
  2. Apply the vendor's fix or mitigation, before November 17, 2021 if you are bound by CISA's deadline, sooner if it faces the internet.
  3. Assume it was tried against you already: look for signs of exploitation from the date it was added, not from the day you patched.
  4. Until every instance is patched, block the attack at the edge: a WAF in blocking mode stops path traversal attempts.

References

CVE-2021-20023 in the National Vulnerability Database

The Dome

Block it at the edge while you patch

The Dome's WAF runs the OWASP Core Rule Set in blocking mode and stops path traversal attempts before they reach your application.

See the Dome

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Source: CISA Known Exploited Vulnerabilities Catalog (public domain), catalog version 2026.10.01.