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Exploited. On CISA's list since 2021-11-03.
CVE-2021-27562 · Arm Trusted Firmware · Published 2021-05-25
5.5 out of 10
CVSS rates it medium.
3.1%
Estimated chance of exploitation in the next 30 days, higher than 87% of all scored flaws (EPSS, 2026-10-29).
Yes
CISA has seen it exploited in real attacks. For US government agencies the fix is deadline passed 1808 days ago (2021-11-17).
Apply updates per vendor instructions.
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.
In Arm Trusted Firmware M through 1.2, the NS world may trigger a system halt, an overwrite of secure data, or the printing out of secure data when calling secure functions under the NSPE handler mode.
From the NVD.
Explore this week’s weaknesses and all learning topics
Understand the kind of weakness behind this flaw. These resources teach the weakness, rather than reproduce this specific CVE. Follow the vendor's advice above to fix the affected product.
A program writes outside the memory region it is allowed to use.
CWE-787 · CISA KEV; NVD record: 134c704f-9b21-4f2e-91b3-4a467353bcc0; NVD record: nvd@nist.gov
Video course · Free course. C programming and memory concepts are useful; covers several weakness types.
CWE is a catalogue of weakness types. Labels come from the sources shown and can differ or change. Resource matches reviewed 16 October 2026.
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Exploited flaws from CISA's KEV catalogue. Chance of exploitation from EPSS by FIRST. Descriptions and scores from the NVD. This product uses the NVD API but is not endorsed or certified by the NVD.