CVE-2026-109832 in Red Hat
Summary
by MITRE • 10/13/2026
A flaw was found in gnome-remote-desktop as shipped in Red Hat Enterprise Linux. In the VNC TLS I/O handlers, retryable GnuTLS results (GNUTLS_E_AGAIN and GNUTLS_E_INTERRUPTED) are handled with an unbounded busy loop instead of yielding to the event loop. A remote attacker who can reach an enabled VNC TLS listener can cause the event-loop thread to spin at high CPU with no forward progress, resulting in denial of service.
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Analysis
by VulDB Data Team • 10/15/2026
The vulnerability identified within gnome-remote-desktop on Red Hat Enterprise Linux represents a significant resource exhaustion flaw rooted in improper error handling during secure network communications. Specifically, this issue resides within the Virtual Network Computing TLS I/O handlers that manage encrypted data streams using GnuTLS. When establishing or maintaining a VNC session over TLS, the application relies on an event loop to process asynchronous input and output operations efficiently. However, when the underlying cryptographic library returns retryable status codes such as GNUTLS_E_AGAIN or GNUTLS_E_INTERRUPTED, indicating that the operation would block if not handled asynchronously, the current implementation fails to yield control back to the main event loop. Instead of pausing execution until the socket is ready for further I/O operations, the software enters an unbounded busy loop. This design flaw prevents the thread from performing any other tasks or sleeping, effectively monopolizing a CPU core indefinitely while waiting for conditions that may never resolve in a timely manner under certain network states or attacker-induced delays.
From a technical perspective, this behavior constitutes a classic denial of service vector driven by inefficient concurrency control and lack of proper blocking semantics. In asynchronous programming models common in desktop environments like GNOME, yielding to the event loop is critical for maintaining system responsiveness and preventing thread starvation. By spinning continuously without releasing the processor time slice, the affected process consumes one hundred percent of a CPU core's capacity. This high-CPU state can lead to broader system instability, affecting not only the remote desktop service but also other applications running on the host machine due to resource contention. The flaw is particularly dangerous because it requires no authentication or complex exploitation techniques; any entity capable of reaching the enabled VNC TLS listener port can trigger this condition simply by initiating a connection and manipulating network conditions to provoke these specific GnuTLS return codes repeatedly.
The operational impact of this vulnerability is severe, primarily manifesting as a denial of service against both the targeted system and potentially other services sharing its resources. An attacker who has network access to the VNC port can cause the gnome-remote-desktop process to consume excessive CPU cycles indefinitely. This results in unresponsive user interfaces on the affected machine, inability for legitimate users to establish new sessions, and potential degradation of performance for critical background processes. In environments where system stability is paramount, such as enterprise workstations or servers running remote management tools, this flaw can render the host unusable until the offending process is manually terminated by an administrator with appropriate privileges. The lack of forward progress means that automated recovery mechanisms relying on normal application behavior may fail to detect and mitigate the issue promptly.
Mitigation strategies should focus on both immediate remediation and long-term architectural improvements. Administrators running Red Hat Enterprise Linux systems affected by this flaw are advised to apply the vendor-provided software updates as soon as they become available, which will patch the I/O handler logic to correctly yield control during retryable GnuTLS states. In the interim, if updating is not immediately feasible, restricting network access to the VNC TLS port via firewall rules can prevent remote exploitation by limiting connectivity to trusted IP ranges only. Furthermore disabling the gnome-remote-desktop service entirely on systems where it is not required reduces the attack surface significantly. From a development standpoint, future iterations must ensure that all asynchronous I/O operations properly integrate with the event loop framework, utilizing non-blocking calls and appropriate sleep or poll mechanisms when retryable errors occur to prevent CPU starvation.
This vulnerability aligns with CWE-400, which describes uncontrolled resource consumption, specifically in the context of a busy wait loop leading to denial of service. It also relates to CWE-835 regarding loops that do not terminate properly due to logic errors rather than explicit infinite constructs. In terms of offensive security frameworks, this flaw can be leveraged within MITRE ATT&CK technique T1499, Endpoint Denial of Service, where an adversary uses resource exhaustion methods to disrupt the availability of a system or service. The simplicity of triggering this condition highlights the importance of rigorous testing for asynchronous I/O patterns in desktop environment components that expose network services, ensuring that error handling paths do not inadvertently create performance bottlenecks exploitable by remote actors.