CVE-2023-42822 in xrdp
Summary
by MITRE • 10/25/2023
xrdp is an open source remote desktop protocol server. Access to the font glyphs in xrdp_painter.c is not bounds-checked . Since some of this data is controllable by the user, this can result in an out-of-bounds read within the xrdp executable. The vulnerability allows an out-of-bounds read within a potentially privileged process. On non-Debian platforms, xrdp tends to run as root. Potentially an out-of-bounds write can follow the out-of-bounds read. There is no denial-of-service impact, providing xrdp is running in forking mode. This issue has been addressed in release 0.9.23.1. Users are advised to upgrade. There are no known workarounds for this vulnerability.
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Analysis
by VulDB Data Team • 05/17/2025
The xrdp remote desktop protocol server represents a critical security vulnerability identified as CVE-2023-42822, which stems from inadequate bounds checking within the xrdp_painter.c source file. This flaw specifically targets the handling of font glyphs, creating a scenario where user-controllable data can trigger unauthorized memory access patterns. The vulnerability exists within the core rendering components of the xrdp service, making it particularly dangerous as it operates within a privileged execution context. When examining the technical implementation, the lack of proper input validation allows attackers to craft malicious font data that exceeds the allocated buffer boundaries, potentially exposing sensitive memory regions.
The operational impact of this vulnerability extends beyond simple memory corruption, as it creates potential pathways for information disclosure and privilege escalation. In non-Debian distributions, xrdp typically executes with root privileges, which transforms this out-of-bounds read condition into a severe security risk. The vulnerability's potential for follow-on exploitation becomes apparent when considering that an out-of-bounds read can often serve as a precursor to more serious attacks such as out-of-bounds write operations. This chaining potential makes the vulnerability particularly concerning for environments where xrdp serves as a primary remote access solution.
Security researchers have classified this vulnerability under the broader context of memory safety issues, with strong correlations to CWE-125 (Out-of-Bounds Read) and potentially CWE-787 (Out-of-Bounds Write) when considering the exploitation chain. The ATT&CK framework would categorize this as a privilege escalation technique through memory corruption, specifically leveraging the concept of "Exploitation for Privilege Escalation" where initial access leads to elevated system privileges. The vulnerability's presence in a remote desktop service makes it particularly attractive to threat actors who seek persistent access to target networks, as xrdp typically operates as a network service with minimal monitoring.
The mitigation strategy for CVE-2023-42822 centers exclusively on upgrading to version 0.9.23.1 or later, as no workarounds exist for this particular flaw. Organizations should prioritize this update across all systems running xrdp services, particularly those where the service operates with elevated privileges. The vulnerability's nature as a bounds checking failure suggests that additional defensive programming practices such as address sanitization and memory protection mechanisms should be considered as part of a broader security posture. Network segmentation and access controls should remain in place as additional layers of defense, though they cannot replace the fundamental need for patching this memory safety issue. The absence of a denial-of-service impact in forking mode does not diminish the severity of this vulnerability, as the potential for information disclosure and privilege escalation remains significant across all affected configurations.