CVE-2026-104042 in Red Hat
Summary
by MITRE • 10/06/2026
A flaw was found in sssd. A local attacker can cause a Denial of Service (DoS) by sending a crafted Pluggable Authentication Module (PAM) request containing a zero-length authentication token to the responder socket. Due to missing input validation, the service attempts to read beyond buffer boundaries when processing the token, causing the PAM responder to crash.
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Analysis
by VulDB Data Team • 10/06/2026
The System Security Services Daemon serves as a critical component in Linux and Unix environments for managing identity access control mechanisms such as LDAP, Active Directory, and local files. It provides essential services including authentication, authorization, account management, and name resolution through various interfaces, most notably the Pluggable Authentication Module interface. The security of this daemon is paramount because it acts as a gatekeeper for system access, meaning any compromise or instability in its operation can lead to significant disruptions in service availability. In recent assessments, researchers have identified a critical flaw within the PAM responder component that allows local attackers to trigger a denial of service condition through malformed input handling.
The technical root cause of this vulnerability lies in insufficient validation of incoming authentication tokens during the processing phase of the Pluggable Authentication Module requests. Specifically, when the daemon receives a crafted request containing a zero-length authentication token, it fails to verify the length or validity of the data before attempting to process it. This lack of input sanitization leads directly to an out-of-bounds memory read operation. Instead of gracefully rejecting empty or invalid tokens as expected by secure coding standards, the service attempts to access memory locations beyond the allocated buffer boundaries associated with the token field.
This improper handling results in a crash of the PAM responder process within SSSD. Because the daemon typically runs as a privileged system service responsible for authenticating users against backend identity providers, its sudden termination disrupts all ongoing and subsequent authentication attempts on the affected host. Local attackers who possess any level of shell access can exploit this flaw by sending specifically crafted requests to the responder socket. The impact is immediate and severe in terms of availability, as legitimate users are unable to log in or maintain sessions until the service is manually restarted. This represents a classic denial of service scenario where resource exhaustion or process failure prevents authorized use of the system.
From a classification perspective, this vulnerability aligns with CWE-125, which describes Out-of-bounds Read vulnerabilities resulting from improper validation of user-supplied input leading to memory access violations. Furthermore, in terms of tactical behavior within the MITRE ATT&CK framework, this exploitation technique falls under Tactic TA0004 Impact and specifically relates to techniques that disrupt service availability such as Resource Hijacking or Service Stop via process termination. The attack vector is classified as Local because it requires an attacker to have prior access to the system shell, distinguishing it from remote code execution vulnerabilities but maintaining high severity due to the critical nature of authentication services.
Mitigation strategies for this vulnerability primarily involve applying vendor-provided patches that update the SSSD package to a version where input validation has been strengthened. Administrators should ensure that their systems are updated with the latest security errata released by their respective distribution maintainers, as these updates typically include fixes for buffer boundary checks and stricter enforcement of token length requirements before processing begins. In environments where immediate patching is not feasible due to operational constraints, implementing strict file permissions on the SSSD socket can limit access to trusted users only, thereby reducing the attack surface available to local attackers who might attempt to exploit this flaw. Additionally, monitoring system logs for unexpected termination of sssd processes can aid in early detection and rapid response to potential exploitation attempts.