In FreeRDP less than or equal to 2.0.0, there is an out-of-bounds read in rfx_process_message_tileset. Invalid data fed to RFX decoder results in garbage on screen (as colors). This has been patched in 2.1.0. References: https://github.com/FreeRDP/FreeRDP/security/advisories/GHSA-5mr4-28w3-rc84 https://pub.freerdp.com/cve/CVE-2020-11043/
Created freerdp tracking bugs for this issue: Affects: fedora-all [bug 1848039] Created freerdp1.2 tracking bugs for this issue: Affects: fedora-all [bug 1848040]
This flaw affects the freerdp CLIENT. In libfreerdp/codec/rfx.c's rfx_process_message_tileset() routine, blockLen is populated by parsing a UINT32 from the input stream. If an incorrect value is supplied and parsed into blockLen, a subsequent stream length check will pass even if there is not enough bytes left in the stream, which can lead to an out-of-bounds read. The length check looks like: if (Stream_GetRemainingLength(s) < blockLen - 6) . Thus, if blockLen == 6, then the check will pass even if the remaining stream length is 0 since 0 is not less than 0. After this, the routine reads 13 bytes from the stream, which could be out-of-bounds. This results in undefined behavior that could display garbage tile data on the screen or crash the client. The patch uses Stream_SafeSeek() to ensure the out-of-bounds read won't occur. Upstream patch: https://github.com/FreeRDP/FreeRDP/commit/3a06ce058f690b7fc1edad2f352c453376c2ebfe
Mitigation: To mitigate this flaw, do not use /rfx, /gfx or /network:auto command line options in the freerdp client.
This issue has been addressed in the following products: Red Hat Enterprise Linux 7 Via RHSA-2020:4031 https://access.redhat.com/errata/RHSA-2020:4031
This bug is now closed. Further updates for individual products will be reflected on the CVE page(s): https://access.redhat.com/security/cve/cve-2020-11043
This issue has been addressed in the following products: Red Hat Enterprise Linux 8 Via RHSA-2020:4647 https://access.redhat.com/errata/RHSA-2020:4647