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CVE-2026-66402— FreeRDP before 3.29.0 TLS Certificate Identity Validation Bypass

Quick assessment

Affected
FreeRDP FreeRDP
Exploitation
Public or AI PoC available; prioritize validation
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

FreeRDP是FreeRDP团队开源的一款远程桌面协议(RDP)的实现。 FreeRDP 3.29.0之前版本存在加密问题漏洞，该漏洞源于tls_verify_certificate()、tls_match_hostname()和x509_utils_get_dns_names()函数中的TLS证书身份验证弱点，使用自定义Common Name和DNS SAN字符串匹配而非OpenSSL长度感知的身份验证API，导致NUL字节截断、接受不匹配的DNS SAN条目时匹配Common Name以及不比较IP

CVSS 9.8 · Critical EPSS 0.51% · P42

Possible ATT&CK Techniques 1 AI

T1557 · Adversary-in-the-Middle

Affected Version Matrix 2

VendorProduct Version RangeStatus
FreeRDP FreeRDP < 3.29.0 affected
3.29.0 unaffected
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I. Basic Information for CVE-2026-66402

Vulnerability Information
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Vulnerability Title
FreeRDP before 3.29.0 TLS Certificate Identity Validation Bypass
Source: CVE Program / CVE List V5
Vulnerability Description
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 'victim.example'), (2) accepts a matching Common Name even when non-matching DNS SAN entries are present, and (3) accepts IP-literal targets via DNS/CN matching without comparing iPAddress SANs. Under a trusted or misissued certificate chain, an attacker positioned to present such a certificate can bypass server identity verification, weakening TLS server authentication.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Source: CVE Program / CVE List V5
Vulnerability Type
证书验证不恰当
Source: CVE Program / CVE List V5
Vulnerability Title
FreeRDP 加密问题漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
FreeRDP是FreeRDP团队开源的一款远程桌面协议(RDP)的实现。 FreeRDP 3.29.0之前版本存在加密问题漏洞，该漏洞源于tls_verify_certificate()、tls_match_hostname()和x509_utils_get_dns_names()函数中的TLS证书身份验证弱点，使用自定义Common Name和DNS SAN字符串匹配而非OpenSSL长度感知的身份验证API，导致NUL字节截断、接受不匹配的DNS SAN条目时匹配Common Name以及不比较IP
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
FreeRDP FreeRDP 0 ~ 3.29.0 -

II. Public POCs for CVE-2026-66402

# POC Description Source Link Shenlong Link
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Qwen3.6-35B-A3B · 12475 chars
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III. Intelligence Information for CVE-2026-66402

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Patches & Fixes for CVE-2026-66402 (1)

Vendor Advisories for CVE-2026-66402 (2)

Same Patch Batch · FreeRDP · 2026-08-01 · 21 CVEs total

CVE-2026-67289 9.8 CRITICAL FreeRDP before 3.29.0 HTTP Proxy Request Injection via Redirection
CVE-2026-67305 9.4 CRITICAL FreeRDP Windows Client before 3.29.0 Heap Buffer Overflow via Cliprdr
CVE-2026-67299 7.5 HIGH FreeRDP before 3.29.0 Use-After-Free via WindowIcon async message
CVE-2026-67304 7.5 HIGH FreeRDP before 3.29.0 NULL Dereference via smartcard cleanup
CVE-2026-67297 7.5 HIGH FreeRDP before 3.29.0 Resource Exhaustion via chunked HTTP response
CVE-2026-67301 7.5 HIGH FreeRDP before 3.29.0 Out-of-bounds Read via Polygon async message-proxy
CVE-2026-67290 7.5 HIGH FreeRDP before 3.29.0 Heap Out-of-Bounds Read via TSMF
CVE-2026-67296 7.5 HIGH FreeRDP before 3.29.0 Denial of Service via RDPEI PDU
CVE-2026-67291 7.5 HIGH FreeRDP before 3.29.0 Heap Out-of-Bounds Read via GLYPH_FRAGMENT_ADD
CVE-2026-67300 7.5 HIGH FreeRDP before 3.29.0 Use-After-Free via async message proxy
CVE-2026-67288 7.5 HIGH FreeRDP before 3.29.0 Denial of Service via smartcard cache
CVE-2026-67298 7.5 HIGH FreeRDP 3.28.0 Heap Buffer Overflow via RAIL orderLength Underflow
CVE-2026-67292 6.5 MEDIUM FreeRDP before 3.29.0 WebSocket Ping Buffer Over-disclosure
CVE-2026-67295 6.3 MEDIUM FreeRDP before 3.29.0 Path Traversal via drive redirection
CVE-2026-67294 5.9 MEDIUM FreeRDP before 3.29.0 TLS Certificate EKU Bypass
CVE-2026-67306 5.4 MEDIUM FreeRDP before 3.29.0 Out-of-Bounds Read via Planar RLE
CVE-2026-67303 4.3 MEDIUM FreeRDP before 3.29.0 Denial of Service via serial DeviceControl
CVE-2026-67302 4.3 MEDIUM FreeRDP rdpecam StartStreamsRequest divide-by-zero denial of service
CVE-2026-67293 4.2 MEDIUM FreeRDP before 3.29.0 Improper Certificate Hostname Validation
CVE-2026-66401 2.1 LOW FreeRDP before 3.29.0 Out-of-Bounds Read via UVC H.264

IV. Related Vulnerabilities

Same product: FreeRDP
Same vendor: FreeRDP
Same weakness: CWE-295

V. Comments for CVE-2026-66402

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