Known exploited · Arm
CVE-2021-27562: Arm Trusted Firmware Out-of-Bounds Write Vulnerability
What it is
Arm Trusted Firmware contains an out-of-bounds write vulnerability allowing the non-secure (NS) world to trigger a system halt, overwrite secure data, or print out secure data when calling secure functions under the non-secure processing environment (NSPE) handler mode. This vulnerability affects Yealink Device Management servers.
- Vendor
- Arm
- Product
- Trusted Firmware
- Added to KEV
- November 3, 2021
- CISA due date
- November 17, 2021
- Ransomware use
- Unknown
- Weakness
- CWE-787: Out-of-bounds Write
What CISA requires
Apply updates per vendor instructions.
Forensic triage
No
What to do now
- Find every instance of Trusted Firmware you run, including the forgotten ones, and check its version against the vendor advisory.
- 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.
- Assume it was tried against you already: look for signs of exploitation from the date it was added, not from the day you patched.
References
H2 Security
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Start freeSource: CISA Known Exploited Vulnerabilities Catalog (public domain), catalog version 2026.10.01.