CVE-2020-11044: 
NixOS vulnerability analysis and mitigation

CVE-2020-11044 affects FreeRDP versions greater than 1.2 and before 2.0.0. The vulnerability was discovered in March 2020 and patched in version 2.0.0. The issue exists in the update_read_cache_bitmap_v3_order function where a double free condition can occur when processing corrupted data from a manipulated server (GitHub Advisory).

The vulnerability occurs in the update_read_cache_bitmap_v3_order function where the code first reads new_len from stream and passes it to realloc. If new_len is 0, realloc will free bitmapData->data and return NULL. When new_data is NULL, the code path leads to free_cache_bitmap_v3_order which attempts to free bitmapData->data again, resulting in a double free condition (GitHub Issue). The issue was fixed by adding a check to ensure new_len is greater than 0 before proceeding with the realloc operation (GitHub Commit).

When exploited, this vulnerability causes the FreeRDP client application to crash if corrupted data from a manipulated server is parsed, resulting in a denial of service condition (GitHub Advisory).

The vulnerability can be triggered by a malicious RDP server sending specially crafted bitmap data to a vulnerable FreeRDP client. The severity is rated as Low according to the CVSS scoring system (Ubuntu Security).

The vulnerability has been patched in FreeRDP version 2.0.0. Users are advised to upgrade to version 2.0.0 or later to address this security issue. No workarounds are available for this vulnerability (GitHub Advisory).