Bug 2533959 (CVE-2026-91953)

Summary: CVE-2026-91953 FreeRDP: FreeRDP: Heap buffer overflow via oversized LB_LOAD_BALANCE_INFO routing token can lead to heap corruption.
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security <prodsec-ir-bot>
Status: NEW --- QA Contact:
Severity: medium Docs Contact:
Priority: medium    
Version: unspecifiedCC: rhel-process-autobot, watson-tool-maintainers
Target Milestone: ---Keywords: Security
Target Release: ---   
Hardware: All   
OS: Linux   
Whiteboard:
Fixed In Version: Doc Type: ---
Doc Text:
A flaw was found in FreeRDP. A malicious RDP (Remote Desktop Protocol) server or a man-in-the-middle attacker could exploit a heap buffer overflow vulnerability during connection negotiation, prior to authentication. By sending a specially crafted Server Redirection PDU (Protocol Data Unit) with an oversized LB_LOAD_BALANCE_INFO field, an attacker could cause a denial of service or heap corruption on the client system.
 Story Points: ---
Clone Of: Environment:
Last Closed: Type: ---
Regression: --- Mount Type: ---
Documentation: --- CRM:
Verified Versions: Category: ---
oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: --- Target Upstream Version:
Embargoed:
Bug Depends On: 2534072, 2534073    
Bug Blocks:    

Description OSIDB Bzimport 2026-09-15 15:52:13 UTC 
FreeRDP versions before 3.31.0 contain a heap buffer overflow vulnerability in nego_send_negotiation_request() that fails to validate the LB_LOAD_BALANCE_INFO field length before writing to a fixed 512-byte buffer. A malicious RDP server or man-in-the-middle can send a Server Redirection PDU with an oversized LB_LOAD_BALANCE_INFO value to overflow the buffer with attacker-controlled content, causing denial of service or heap corruption before authentication completes.
Comment 1 Jon Orris 2026-10-05 04:23:37 UTC 
This issue has been addressed in the following products:

  Red Hat Enterprise Linux 10

Via RHSA-2026:75570 https://access.redhat.com/errata/RHSA-2026:75570
Comment 2 Jon Orris 2026-10-06 14:28:33 UTC 
This issue has been addressed in the following products:

  Red Hat Enterprise Linux 8

Via RHSA-2026:76747 https://access.redhat.com/errata/RHSA-2026:76747
Comment 3 Jon Orris 2026-10-08 06:53:07 UTC 
This issue has been addressed in the following products:

  Red Hat Enterprise Linux 9

Via RHSA-2026:76755 https://access.redhat.com/errata/RHSA-2026:76755