FreeRDP is a free implementation of the Remote Desktop Protocol. Prior to version 3.21.0, in ClearCodec, when glyphData is present, clear_decompress calls freerdp_image_copy_no_overlap without validating the destination rectangle, allowing an out-of-bounds read/write via crafted RDPGFX surface updates. A malicious server can trigger a client‑side heap buffer overflow, causing a crash (DoS) and potential heap corruption with code‑execution risk depending on allocator behavior and surrounding heap layout. Version 3.21.0 contains a patch for the issue.
Weakness
A heap overflow condition is a buffer overflow, where the buffer that can be overwritten is allocated in the heap portion of memory, generally meaning that the buffer was allocated using a routine such as malloc().
Affected Software
| Name | Vendor | Start Version | End Version |
|---|---|---|---|
| Freerdp | Freerdp | * | 3.21.0 (excluding) |
| Red Hat Enterprise Linux 10 | RedHat | freerdp-2:3.10.3-5.el10_1.1 | * |
| Red Hat Enterprise Linux 10.0 Extended Update Support | RedHat | freerdp-2:3.10.3-3.el10_0.1 | * |
| Red Hat Enterprise Linux 7 Extended Lifecycle Support | RedHat | freerdp-0:2.1.1-5.el7_9.1 | * |
| Red Hat Enterprise Linux 8 | RedHat | freerdp-2:2.11.7-2.el8_10 | * |
| Red Hat Enterprise Linux 9 | RedHat | freerdp-2:2.11.7-1.el9_7.1 | * |
| Red Hat Enterprise Linux 9.0 Update Services for SAP Solutions | RedHat | freerdp-2:2.4.1-3.el9_0 | * |
| Red Hat Enterprise Linux 9.2 Update Services for SAP Solutions | RedHat | freerdp-2:2.4.1-6.el9_2.2 | * |
| Red Hat Enterprise Linux 9.4 Extended Update Support | RedHat | freerdp-2:2.11.2-1.el9_4.1 | * |
| Freerdp2 | Ubuntu | esm-apps/noble | * |
| Freerdp2 | Ubuntu | esm-infra/bionic | * |
| Freerdp2 | Ubuntu | esm-infra/focal | * |
| Freerdp2 | Ubuntu | jammy | * |
| Freerdp2 | Ubuntu | noble | * |
| Freerdp3 | Ubuntu | noble | * |
| Freerdp3 | Ubuntu | questing | * |
| Freerdp3 | Ubuntu | upstream | * |
Potential Mitigations
- Use automatic buffer overflow detection mechanisms that are offered by certain compilers or compiler extensions. Examples include: the Microsoft Visual Studio /GS flag, Fedora/Red Hat FORTIFY_SOURCE GCC flag, StackGuard, and ProPolice, which provide various mechanisms including canary-based detection and range/index checking.
- D3-SFCV (Stack Frame Canary Validation) from D3FEND [REF-1334] discusses canary-based detection in detail.
- Run or compile the software using features or extensions that randomly arrange the positions of a program’s executable and libraries in memory. Because this makes the addresses unpredictable, it can prevent an attacker from reliably jumping to exploitable code.
- Examples include Address Space Layout Randomization (ASLR) [REF-58] [REF-60] and Position-Independent Executables (PIE) [REF-64]. Imported modules may be similarly realigned if their default memory addresses conflict with other modules, in a process known as “rebasing” (for Windows) and “prelinking” (for Linux) [REF-1332] using randomly generated addresses. ASLR for libraries cannot be used in conjunction with prelink since it would require relocating the libraries at run-time, defeating the whole purpose of prelinking.
- For more information on these techniques see D3-SAOR (Segment Address Offset Randomization) from D3FEND [REF-1335].