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Exploited vulnerability · CISA KEV

Is CVE-2021-27562 exploited? Yes: in CISA KEV since 3 Nov 2021

Gociux · Arm Trusted Firmware · data: CISA KEV, CVE record, FIRST EPSS

Yes. CVE-2021-27562, Arm Trusted Firmware Out-of-Bounds Write Vulnerability, is being exploited in the wild. CISA added it to its Known Exploited Vulnerabilities catalog on 3 Nov 2021, 162 days after it was published. It affects Arm Trusted Firmware. If you run it, CISA's required action is: Apply updates per vendor instructions.

exploitedYesCISA KEV · 3 Nov 2021
ransomwareNot knownno confirmed use
EPSSbelow top 10%lower predicted activity right now (it is still confirmed exploited)
severity5.5CVSS 3.1 · medium
US federal due17 Nov 2021BOD 22-01 deadline

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.

VendorArm (9 exploited CVEs in KEV)
ProductTrusted Firmware
VulnerabilityArm Trusted Firmware Out-of-Bounds Write Vulnerability
WeaknessCWE-787
Published25 May 2021
Added to KEV3 Nov 2021
Reported by (CNA)mitre

What to do

  1. Check whether you run it. Look for Trusted Firmware in your asset inventory, including appliances and cloud images. Stack check lists every exploited Arm CVE at once.
  2. Apply the fix. Apply updates per vendor instructions.
  3. If you can't patch today, take the affected service off the internet or restrict who can reach it, and check its logs for signs of compromise since 25 May 2021.
  4. Get told next time. Email alerts when CISA adds a CVE for Arm.

References

Questions

Is CVE-2021-27562 being exploited?

Yes. CISA added CVE-2021-27562 to the Known Exploited Vulnerabilities catalog on 3 Nov 2021, which means there is reliable evidence of exploitation in the wild.

Is CVE-2021-27562 used in ransomware attacks?

CISA does not list known ransomware use for it. That can change, and exploitation alone is reason to fix it first.

How do I fix CVE-2021-27562?

Apply updates per vendor instructions. Check Arm's advisory for the fixed versions, and if you can't patch quickly, restrict access to the affected Trusted Firmware and watch it for signs of compromise.

Sources: CISA KEV (exploitation, ransomware use, required action, due date), the CVE record (publication date, CVSS, CNA), NVD and FIRST EPSS (live score). More: all KEV additions in November 2021 · Arm scorecard · act-now radar.

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