CVE-2026-73282 in OpenSSH
Summary
by MITRE • 08/11/2026
In ssh in OpenSSH before 10.5, a use-after-free for realloc data can occur if a certain pair of remote-forwarding operations are concurrent.
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Analysis
by VulDB Data Team • 08/12/2026
The vulnerability in OpenSSH versions prior to 10.5 represents a critical use-after-free condition that emerges during concurrent remote forwarding operations. This flaw occurs when specific combinations of remote forwarding commands are executed simultaneously, creating a race condition that allows for improper memory management. The issue stems from the ssh daemon's handling of realloc operations within the remote forwarding code path, where freed memory locations are accessed after reallocation has occurred. Such memory corruption vulnerabilities are particularly dangerous as they can lead to arbitrary code execution or denial of service conditions.
The technical implementation of this vulnerability involves the ssh daemon's internal memory management routines that handle concurrent remote forwarding requests. When two remote forwarding operations occur simultaneously, the realloc function may return a pointer to memory that has already been freed by another operation in the same thread or process. This creates a scenario where subsequent memory access operations target deallocated memory regions, potentially leading to heap corruption and unpredictable behavior.
From an operational perspective, this vulnerability presents significant risks to systems relying on OpenSSH for secure remote access and tunneling operations. Attackers could exploit this condition by carefully orchestrating concurrent remote forwarding requests to trigger the use-after-free scenario, potentially gaining unauthorized access to the target system or causing service disruption. The vulnerability affects both client and server implementations of OpenSSH, making it particularly concerning for environments where multiple concurrent SSH sessions or forwarding operations are common.
Security implications extend beyond immediate exploitation potential as this type of memory corruption can serve as a foundation for more sophisticated attacks within the context of the ATT&CK framework's privilege escalation and execution techniques. The vulnerability aligns with CWE-416 which specifically addresses use-after-free conditions, making it a well-documented and dangerous class of memory safety issue. Organizations should prioritize immediate patching of affected OpenSSH installations to mitigate this risk, as the vulnerability represents a fundamental flaw in memory management that could be leveraged for system compromise.
Mitigation strategies include applying the official OpenSSH 10.5 patch which addresses the specific race condition in remote forwarding operations and implementing monitoring for unusual concurrent SSH forwarding activities. System administrators should also consider limiting concurrent remote forwarding operations where possible and implementing additional security controls around SSH access. The fix implemented in version 10.5 resolves the memory management issue by ensuring proper synchronization of realloc operations during concurrent remote forwarding scenarios, preventing the access to freed memory that previously enabled exploitation of this vulnerability.