Is CVE-2025-66738 exploited in the wild?

No. Junglewise Threat Intelligence has no report of CVE-2025-66738 being exploited in the wild.

How severe is CVE-2025-66738?

High severity, with a CVSS score of 8.8, published 26 December 2025.

Which products and versions are affected?

Yealink T21P E2 IP Phone 52.84.0.15.

Is there a fix for CVE-2025-66738?

No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

How is CVE-2025-66738 attacked?

It is attacked over the network, in a network appliance.

Am I affected by CVE-2025-66738?

Check whether you run Yealink Sip-T21\(P\)E2, Yealink Sip-T21\(P\)E2 Firmware or Yealink T21P E2 IP Phone at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

CVE-2025-66738: Yealink T21P_E2 command injection in diagnostic ping function

CVE-2025-66738 · Severity: high · CVSS 8.8 · Published 2025-12-26

A security vulnerability exists in Yealink T21P_E2 VoIP phones that could allow an authorized user to take full control of the device. By sending a specially crafted request to the phone's diagnostic tools, an attacker can execute unauthorized commands. This could lead to eavesdropping on calls, disruption of phone services, or using the device as a foothold to attack other parts of the corporate network.

Vendors: Yealink.

Quick answers

Is CVE-2025-66738 exploited in the wild?: No. Junglewise Threat Intelligence has no report of CVE-2025-66738 being exploited in the wild.
How severe is CVE-2025-66738?: High severity, with a CVSS score of 8.8, published 26 December 2025.
Which products and versions are affected?: Yealink T21P E2 IP Phone 52.84.0.15.
Is there a fix for CVE-2025-66738?: No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.
How is CVE-2025-66738 attacked?: It is attacked over the network, in a network appliance.
Am I affected by CVE-2025-66738?: Check whether you run Yealink Sip-T21\(P\)E2, Yealink Sip-T21\(P\)E2 Firmware or Yealink T21P E2 IP Phone at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

Technical details

A command injection vulnerability (CWE-77) exists in the Yealink T21P_E2 phone running firmware version 52.84.0.15. The flaw is located within the ping function of the diagnostic component, which fails to properly neutralize special elements in user-supplied input. A remote attacker with 'normal' (low) privileges can exploit this by sending a crafted request to the web management interface. Successful exploitation allows for arbitrary code execution with the privileges of the web service, potentially leading to full system compromise. A proof-of-concept has been identified in public disclosures.

Affected products

Yealink T21P_E2 Phone 52.84.0.15

Timeline

2025-12-26: disclosed
2025-12-26: advisory

References

https://drive.google.com/file/d/13t5ywSPJMx4487njJcH3ZTNuc_k3h4ty/view?usp=sharing

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