CVE-2025-66738: An issue in Yealink T21P_E2 Phone 52.84.0.15 allows a remote normal privileged attacker to execute arbitrary c

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HIGH 8.8MITIGATE

CVE-2025-66738 is a high-severity flaw (CVSS 8.8) affecting sip-t21\(p\)e2 firmware. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

An issue in Yealink T21P_E2 Phone 52.84.0.15 allows a remote normal privileged attacker to execute arbitrary code via a crafted request the ping function of the diagnostic component.

Why this priority

High severity
Public exploit reference

No fix is published yet: follow the downgrade or mitigation steps.

Risk facts

CVSS score	8.8 (High)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	Low
User interaction	None
EPSS exploit chance	0.6% (top 51%)
CISA exploited list	No
Weakness	CWE-77
Published	2025-12-26
Last modified	2026-10-07

Publisher (CNA): MITRE · Vendor: yealink

Last updated 2026-10-07 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2025-12-26 16:15 UTCPublished CVE record published
2026-10-07 13:10 UTCUpdated Record last modified

yealink sip-t21\(p\)e2 firmware MITIGATE

Affected: 52.84.0.15

Fixed in: no fixed release known

Safe to downgrade to: a release before 52.84.0.15

Check your OS release

cat /etc/os-release; uname -r

Debian / Ubuntu

sudo apt update && sudo apt full-upgrade

RHEL / Amazon Linux / Fedora

sudo dnf upgrade --refresh

Windows

Install the latest cumulative update from Windows Update

If no patch exists yet

OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2025-66738?

sip-t21\(p\)e2 firmware: mitigate or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2025-66738 being exploited?

CVE-2025-66738 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2025-66738 affect?

CVE-2025-66738 affects sip-t21\(p\)e2 firmware. Severity is high (CVSS 8.8). An issue in Yealink T21P_E2 Phone 52.84.0.15 allows a remote normal privileged attacker to execute arbitrary code via a crafted request the ping function of the diagnostic component.

How urgent is CVE-2025-66738?

Priority 48/100. High severity; Public exploit reference

Related CVEs

CVE-2025-66737 MEDIUM 4.3 MITIGATE Yealink T21P_E2 Phone 52.84.0.15 is vulnerable to Directory Traversal

References

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