What is CVE-2021-35394?

CVE-2021-35394 is a critical-severity vulnerability in Realtek Rtl819x Jungle Software Development Kit, classified under OS Command Injection. CVSS score: 9.8/10. Published 2021-08-16.

How severe is CVE-2021-35394?

Critical severity. CVSS v3 base score is 9.8 out of 10.

Is CVE-2021-35394 known to be exploited?

Yes. CVE-2021-35394 is listed in the CISA Known Exploited Vulnerabilities catalog (added 2021-12-10), indicating it is being actively exploited. 4 public proof-of-concept repositories are indexed.

RCE in Realtek Rtl819x Jungle Software Development Kit

CVE-2021-35394

Realtek Jungle SDK version v2.x up to v3.4.14B provides a diagnostic tool called 'MP Daemon' that is usually compiled as 'UDPServer' binary. The binary is affected by multiple memory corruption vulnerabilities and an arbitrary command injection vulnerability that can be exploited by remote unauthenticated attackers.

Vulnerability class: Command Injection (OS Command Injection)

Published 2021-08-16 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 9.8 (Critical). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.

EPSS exploit prediction

EPSS: 0.999 (100.0th percentile), scored 2026-10-08.

Very high probability of exploitation in the next 30 days — among the top 0.1% most-likely-to-be-exploited CVEs. 100th percentile — 100.0% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.999 · newest: 0.999 · change: +0.000

Affected products

Realtek Rtl819x Jungle Software Development Kit

Weakness classification (CWE)

CWE-78 — OS Command Injection

CISA KEV (Known Exploited Vulnerabilities)

This CVE is on the CISA KEV catalog, added on 2021-12-10. CISA KEV inclusion means CISA has confirmed in-the-wild exploitation; US federal agencies are required to remediate within a published due date.

BOD 22-01 due date: 2021-12-24.

Required action: Apply updates per vendor instructions.

Public proof-of-concept exploits

References

www.securityfocus.com/archive/1/534765 (VDB Entry, Third Party Advisory, Broken Link)
www.realtek.com/en/cu-1-en/cu-1-taiwan-en (Patch, Broken Link, Vendor Advisory)
www.realtek.com/images/safe-report/Realtek_APRouter_SDK_Advisory-CVE-2021-35392… (Patch, Vendor Advisory)
www.iot-inspector.com/blog/advisory-multiple-issues-realtek-sdk-iot-supply-chain (Exploit, Third Party Advisory, Broken Link)
134c704f-9b21-4f2e-91b3-4a467353bcc0 (US Government Resource)

Frequently asked questions

What is CVE-2021-35394?: CVE-2021-35394 is a critical-severity vulnerability in Realtek Rtl819x Jungle Software Development Kit, classified under OS Command Injection. CVSS score: 9.8/10. Published 2021-08-16.
How severe is CVE-2021-35394?: Critical severity. CVSS v3 base score is 9.8 out of 10.
Is CVE-2021-35394 known to be exploited?: Yes. CVE-2021-35394 is listed in the CISA Known Exploited Vulnerabilities catalog (added 2021-12-10), indicating it is being actively exploited. 4 public proof-of-concept repositories are indexed.