CVE-2026-26955
HighCVSS 8.8Exploitation Probability (EPSS)
Low risk42th percentile - higher than 42% of all known CVEs
Summary
In FreeRDP prior to version 3.23.0, a heap buffer overflow vulnerability exists in clients using the GDI surface pipeline. A malicious RDP server can send an RDPGFX ClearCodec surface command with an out-of-bounds destination rectangle, causing a write beyond allocated memory. This allows overwriting the `codecs*` pointer in the `gdiGfxSurface` structure, leading to arbitrary code execution.
Risk Assessment
The organization is at risk of remote code execution on FreeRDP client machines via a malicious RDP server. An attacker could gain full control of the victim's system, leading to data theft, malware installation, or lateral movement within the network.
Recommendation
Upgrade FreeRDP to version 3.23.0 or later immediately, which includes a fix for this vulnerability. If upgrading is not possible, restrict RDP connections to trusted servers only.
Other vulnerabilities in FreeRDP
See all- CVE-2026-23732High
FreeRDP before version 3.21.0 has a vulnerability in FastGlyph parsing where data length is not validated against the minimum size implied by cx/cy. A malicious server can trigger a client-side global buffer overflow, causing a crash (DoS).
- CVE-2026-22856High
FreeRDP is a free implementation of the Remote Desktop Protocol. Prior to 3.20.1, a race in the serial channel IRP thread tracking allows a heap use‑after‑free when one thread removes an entry from serial->IrpThreads while another reads it. This vulnerability is fixed in 3.20.1.
- CVE-2013-4119High
FreeRDP before 1.1.0-beta+2013071101 allows remote attackers to cause a denial of service (NULL pointer dereference and application crash) by disconnecting before authentication has finished.
- CVE-2013-4118High
FreeRDP before 1.1.0-beta1 allows remote attackers to cause a denial of service via NULL pointer dereference, leading to application crash.
- CVE-2014-0250High
Multiple integer overflows in client/X11/xf_graphics.c in FreeRDP allow remote attackers to have an unspecified impact via the width and height to the xf_Pointer_New or xf_Bitmap_Decompress function, which causes an incorrect amount of memory to be allocated.
- CVE-2026-91949Critical
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.
- CVE-2026-63633Critical
In FreeRDP before 3.28.0, freerdp_dsp_decode_opus calls Stream_EnsureRemainingCapacity on the context buffer even though opus_decode writes to the caller-supplied stream. A malicious RDP server negotiating WAVE_FORMAT_OPUS can cause large decoded frames to be written beyond the allocated buffer, leading to client heap corruption, crash, and potential code execution.
- CVE-2026-55194Critical
In FreeRDP before 3.27.0, rpc_client_recv_fragment ensures response reassembly stream capacity using only the server-declared alloc_hint rather than the actual StubLength. A malicious TS Gateway can send a response with a small alloc_hint and a much larger frag_length, causing a buffer overflow in the pdu->s buffer. This can crash the client and may permit code execution.
- CVE-2026-55191Critical
In FreeRDP before 3.27.0, clients negotiating RDPGFX AVC444 calculate the intermediate YUV444 allocation size using 32-bit multiplication in avc444_ensure_buffer. A malicious RDP server can supply surface dimensions causing integer wrap, leading to an undersized buffer allocation. This can cause a client crash and may permit code execution.
- CVE-2026-73242Critical
FreeRDP, a free implementation of the Remote Desktop Protocol, prior to version 3.30.0 has a vulnerability in the kerberos_DecryptMessage function that fails to bound the peer-controlled GSS Wrap-token EC field before using it with RRC in IOV pointer offsets. A malicious RDP peer can trigger out-of-bounds reads and in-place writes during CredSSP/NLA Kerberos decryption.
Original NVD description (English source)
FreeRDP is a free implementation of the Remote Desktop Protocol. Prior to version 3.23.0, a malicious RDP server can trigger a heap buffer overflow in FreeRDP clients using the GDI surface pipeline (e.g., `xfreerdp`) by sending an RDPGFX ClearCodec surface command with an out-of-bounds destination rectangle. The `gdi_SurfaceCommand_ClearCodec()` handler does not call `is_within_surface()` to validate the command rectangle against the destination surface dimensions, allowing attacker-controlled `cmd->left`/`cmd->top` (and subcodec rectangle offsets) to reach image copy routines that write into `surface->data` without bounds enforcement. The OOB write corrupts an adjacent `gdiGfxSurface` struct's `codecs*` pointer with attacker-controlled pixel data, and corruption of `codecs*` is sufficient to reach an indirect function pointer call (`NSC_CONTEXT.decode` at `nsc.c:500`) on a subsequent codec command — full instruction pointer (RIP) control demonstrated in exploitability harness. Users should upgrade to version 3.23.0 to receive a patch.
Vulnerability data from NVD (NIST) · CISA KEV · EPSS