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Exploited vulnerability · CISA KEV

Is CVE-2021-35395 exploited? Yes: in CISA KEV since 3 Nov 2021

Gociux · Realtek AP-Router SDK · data: CISA KEV, CVE record, FIRST EPSS

Yes. CVE-2021-35395, Realtek AP-Router SDK Buffer Overflow Vulnerability, is being exploited in the wild. CISA added it to its Known Exploited Vulnerabilities catalog on 3 Nov 2021, 79 days after it was published. It affects Realtek AP-Router SDK. If you run it, CISA's required action is: Apply updates per vendor instructions.

exploitedYesCISA KEV · 3 Nov 2021
ransomwareNot knownno confirmed use
EPSStop 1%among the most likely CVEs to be exploited
severity9.8CVSS 3.1 · critical
US federal due17 Nov 2021BOD 22-01 deadline

What it is

Realtek AP-Router SDK HTTP web server boa contains a buffer overflow vulnerability due to unsafe copies of some overly long parameters submitted in the form that lead to denial-of-service (DoS).

VendorRealtek (3 exploited CVEs in KEV)
ProductAP-Router SDK
VulnerabilityRealtek AP-Router SDK Buffer Overflow Vulnerability
WeaknessCWE-20, CWE-122
Published16 Aug 2021
Added to KEV3 Nov 2021
Reported by (CNA)mitre

What to do

  1. Check whether you run it. Look for AP-Router SDK in your asset inventory, including appliances and cloud images. Stack check lists every exploited Realtek 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 16 Aug 2021.
  4. Get told next time. Email alerts when CISA adds a CVE for Realtek.

References

Questions

Is CVE-2021-35395 being exploited?

Yes. CISA added CVE-2021-35395 to the Known Exploited Vulnerabilities catalog on 3 Nov 2021, which means there is reliable evidence of exploitation in the wild.

Is CVE-2021-35395 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-2021-35395?

Apply updates per vendor instructions. Check Realtek's advisory for the fixed versions, and if you can't patch quickly, restrict access to the affected AP-Router SDK 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 · Realtek scorecard · act-now radar.

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