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CVE-2026-91949— FreeRDP 3.0.0 through 3.30.0 Protocol Negotiation Bypass

Quick assessment

Affected
FreeRDP FreeRDP
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

FreeRDP 服务器在 3.31.0 版本之前存在协议协商绕过漏洞，允许未经身份验证的攻击者即便服务器策略已禁用，也能建立 RDSTLS 连接。攻击者可发送不兼容的协议请求，在收到协商失败后，仍能完成 TLS 握手并进入 RDSTLS，从而绕过认证前的传输限制。

CVSS 9.3 · Critical

Possible ATT&CK Techniques 1 AI

T1076

Affected Version Matrix 2

VendorProduct Version RangeStatus
FreeRDP FreeRDP 3.0.0< 3.31.0 affected
3.31.0 unaffected
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I. Basic Information for CVE-2026-91949

Vulnerability Information
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Vulnerability Title
FreeRDP 3.0.0 through 3.30.0 Protocol Negotiation Bypass
Source: CVE Program / CVE List V5
Vulnerability Description
FreeRDP server versions before 3.31.0 contain a protocol negotiation bypass vulnerability that allows unauthenticated attackers to establish RDSTLS connections despite server policy disabling them. Attackers can send incompatible protocol requests, receive negotiation failures, then complete TLS handshake and enter RDSTLS to bypass pre-authentication transport restrictions.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:L/A:N
Source: CVE Program / CVE List V5
Vulnerability Type
保护机制失效
Source: CVE Program / CVE List V5

Affected Products

Vendor Product Affected Versions CPE Subscribe
FreeRDP FreeRDP 3.0.0 ~ 3.31.0 -

II. Public POCs for CVE-2026-91949

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III. Intelligence Information for CVE-2026-91949

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Vendor Advisories for CVE-2026-91949 (2)

Same Patch Batch · FreeRDP · 2026-09-15 · 20 CVEs total

CVE-2026-91964 8.8 HIGH FreeRDP 2.0.0 through 3.30.0 Heap Buffer Overflow via RoutingToken
CVE-2026-91955 7.5 HIGH FreeRDP before 3.31.0 Denial of Service via Desktop Dimensions
CVE-2026-91948 7.5 HIGH FreeRDP before 3.31.0 Out-of-bounds Write via SHOW_PROTOCOL
CVE-2026-91947 7.5 HIGH FreeRDP Server before 3.31.0 Use-After-Free via DRDYNVC
CVE-2026-91958 6.6 MEDIUM FreeRDP 3.11.0 through 3.30.0 Heap Buffer Overflow via Monitor Index
CVE-2026-91954 6.5 MEDIUM FreeRDP before 3.31.0 NULL Pointer Dereference via NSCodec
CVE-2026-91956 6.5 MEDIUM FreeRDP before 3.31.0 Out-of-Bounds Read via URBDRC
CVE-2026-91951 6.5 MEDIUM FreeRDP 3.14.0 through 3.30.0 Out-of-bounds Write via urbdrc
CVE-2026-91946 6.5 MEDIUM FreeRDP before 3.31.0 Information Disclosure via RDPGFX ResetGraphics
CVE-2026-91953 6.5 MEDIUM FreeRDP before 3.31.0 Heap Buffer Overflow via LB_LOAD_BALANCE_INFO
CVE-2026-91961 6.5 MEDIUM FreeRDP before 3.31.0 Denial of Service via URBDRC
CVE-2026-91963 6.5 MEDIUM FreeRDP 2.0.0 through 3.30.0 Uninitialized Heap Memory Disclosure via urbdrc
CVE-2026-91952 6.5 MEDIUM FreeRDP before 3.31.0 Denial of Service via pool_decode_rect
CVE-2026-91945 6.5 MEDIUM FreeRDP before 3.31.0 Out-of-bounds Read via Smartcard ATR
CVE-2026-91960 6.5 MEDIUM FreeRDP before 3.31.0 Integer Overflow Double Free
CVE-2026-91959 6.5 MEDIUM FreeRDP before 3.31.0 Buffer Over-read via RTS Gateway
CVE-2026-91950 6.5 MEDIUM FreeRDP before 3.31.0 Out-of-Bounds Read via UINT32 Wraparound
CVE-2026-91962 6.3 MEDIUM FreeRDP before 3.31.0 Integer Overflow via audin Apple backends
CVE-2026-91957 3.1 LOW FreeRDP before 3.31.0 Use-After-Free via smartcard worker

IV. Related Vulnerabilities

Same product: FreeRDP
Same vendor: FreeRDP
Same weakness: CWE-693

V. Comments for CVE-2026-91949

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