CVE-2026-66402: FreeRDP before 3.29.0 (affected versions <= 3.28.0) contains multiple TLS certificate identity validation weak

Q: How do I fix CVE-2026-66402?

freerdp: upgrade to 3.29.0. Exact commands for each OS are on this page.

Q: Is CVE-2026-66402 being exploited?

CVE-2026-66402 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2026-66402 affect?

CVE-2026-66402 affects freerdp. Severity is critical (CVSS 9.8). FreeRDP before 3.29.0 (affected versions <= 3.28.0) contains multiple TLS certificate identity validation weaknesses in tls_verify_certificate(), tls_match_hostname(), and x509_utils_get_dns_names(). Because FreeRDP performs custom Common N

Q: How urgent is CVE-2026-66402?

Priority 51/100. Critical severity; Public exploit reference; Remotely exploitable, no login, no user action

This week

CRITICAL 9.8REMOTEUPGRADE

CVE-2026-66402 is a critical-severity flaw (CVSS 9.8) affecting freerdp. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

FreeRDP before 3.29.0 (affected versions <= 3.28.0) contains multiple TLS certificate identity validation weaknesses in tls_verify_certificate(), tls_match_hostname(), and x509_utils_get_dns_names(). Because FreeRDP performs custom Common Name and DNS SAN string matching instead of using OpenSSL's length-aware identity validation APIs, it (1) truncates DNS SAN values at embedded NUL bytes (accepting e.g. 'victim.example\0.attacker.example' as 'vi

Why this priority

Critical severity
Public exploit reference
Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	9.8 (Critical)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	0.3% (top 73%)
CISA exploited list	No
Weakness	CWE-295
Published	2026-08-01
Last modified	2026-10-02

Publisher (CNA): VulnCheck · Vendor: freerdp

Last updated 2026-10-02 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-08-01 13:16 UTCPublished CVE record published
2026-10-02 19:08 UTCUpdated Record last modified

freerdp freerdp UPGRADE

Affected: < 3.29.0

Fixed in: 3.29.0

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy freerdp || rpm -q freerdp || freerdp --version

2. UPGRADE to 3.29.0 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade freerdp

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade freerdp

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

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-2026-66402?

freerdp: upgrade to 3.29.0. Exact commands for each OS are on this page.

Is CVE-2026-66402 being exploited?

CVE-2026-66402 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-2026-66402 affect?

CVE-2026-66402 affects freerdp. Severity is critical (CVSS 9.8). FreeRDP before 3.29.0 (affected versions <= 3.28.0) contains multiple TLS certificate identity validation weaknesses in tls_verify_certificate(), tls_match_hostname(), and x509_utils_get_dns_names(). Because FreeRDP performs custom Common N

How urgent is CVE-2026-66402?

Priority 51/100. Critical severity; Public exploit reference; Remotely exploitable, no login, no user action

Software pages

OpenSSL vulnerabilities

Related CVEs

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References

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