CVE-2026-12610: Fedoraproject SSSD Use-After-Free Flaw

CVE-2026-12610 Overview

CVE-2026-12610 is a use-after-free vulnerability [CWE-825] in the System Security Services Daemon (SSSD) Pluggable Authentication Module (PAM) responder. The flaw occurs when a user authenticates with a YubiKey or smartcard, where a memory pointer is incorrectly handled after being freed. A local attacker with high privileges can manipulate smartcard or YubiKey contents to crash the PAM responder, causing a denial of service that disrupts authentication across the system. The vulnerability also carries potential for privilege escalation, though exploitation is difficult due to attack complexity. The flaw affects Fedora SSSD and Red Hat Enterprise Linux versions 8, 9, and 10.

Critical Impact
Local attackers can crash the SSSD PAM responder by manipulating smartcard or YubiKey contents, disrupting authentication services and potentially enabling privilege escalation.

Affected Products

Fedora Project SSSD
Red Hat Enterprise Linux 8.0
Red Hat Enterprise Linux 9.0 and 10.0

Discovery Timeline

2026-06-30 - CVE-2026-12610 published to NVD
2026-06-30 - Last updated in NVD database

Technical Details for CVE-2026-12610

Vulnerability Analysis

The vulnerability resides in the SSSD PAM responder, the component responsible for processing authentication requests from the PAM stack. When a user authenticates with a YubiKey or smartcard, the PAM responder allocates and manages memory structures tied to the authentication token. The flaw causes the responder to reference a memory pointer that has already been freed, resulting in a use-after-free condition classified under [CWE-825] (Expired Pointer Dereference).

An attacker with local access and control over the smartcard or YubiKey contents can trigger the flaw during the authentication handshake. Successful exploitation crashes the PAM responder, halting authentication services for all users depending on SSSD. Because SSSD is the identity broker on many enterprise Linux systems, disruption affects login, sudo, and network identity operations.

Root Cause

The root cause is improper lifecycle management of a memory pointer within the PAM responder code path handling smartcard authentication. After the object referenced by the pointer is freed, subsequent code paths continue to dereference it. Attackers can influence the contents read from the token to steer the dereference toward attacker-controlled data.

Attack Vector

Exploitation requires local access and high privileges to place a crafted smartcard or YubiKey in front of the SSSD PAM responder. The attacker manipulates data on the token so that the malformed input drives the PAM responder into the vulnerable code path. Denial of service is the reliable outcome. Privilege escalation is theoretically possible if the attacker can control the freed memory region, but the high attack complexity limits practical exploitation.

No public proof-of-concept exploit is available at the time of publication. The vulnerability is not listed in the CISA Known Exploited Vulnerabilities catalog. The EPSS probability is 0.155%.

Detection Methods for CVE-2026-12610

Indicators of Compromise

Unexpected crashes or restarts of the sssd_pam process recorded in journalctl or /var/log/sssd/sssd_pam.log.
Core dumps generated by SSSD PAM responder processes in /var/lib/systemd/coredump/ or abrt directories.
Authentication failures across multiple users occurring immediately after a smartcard or YubiKey insertion event.
PAM stack error messages referencing SSSD communication failures during smartcard login attempts.

Detection Strategies

Monitor systemd service status for the SSSD service and its PAM child processes, alerting on unexpected termination.
Correlate udev events for smartcard or YubiKey device insertion with subsequent SSSD process crashes.
Deploy audit rules on /etc/sssd/sssd.conf and PAM configuration files to detect changes that could enable exploitation.

Monitoring Recommendations

Forward SSSD logs and systemd journal entries to a centralized SIEM for baseline analysis of authentication reliability.
Track PAM authentication failure rates per host to identify anomalous spikes indicative of exploitation attempts.
Alert on repeated smartcard authentication attempts from the same session that trigger SSSD faults.

How to Mitigate CVE-2026-12610

Immediate Actions Required

Apply vendor patches from Red Hat and Fedora as soon as they are released for the affected SSSD packages.
Restrict physical access to systems that accept smartcard or YubiKey authentication until the patch is applied.
Review which local accounts hold sufficient privileges to attach smartcard devices and reduce that population.
Enable core dump collection and log forwarding for SSSD to capture forensic evidence if the flaw is triggered.

Patch Information

Red Hat tracks the fix under the Red Hat CVE Details advisory and the Red Hat Bug Report. Upstream development and the fix commit are tracked in GitHub SSSD Issue #8796. Administrators should update sssd packages using dnf update sssd on Fedora and Red Hat Enterprise Linux 8, 9, and 10 once fixed versions are published.

Workarounds

Temporarily disable smartcard and YubiKey authentication in /etc/sssd/sssd.conf by removing pam_cert_auth = True until a patched version is deployed.
Fall back to password-based authentication for local console and PAM logins on affected hosts.
Configure systemd to automatically restart the sssd service on failure to reduce the availability impact of a crash.

bash

# Configuration example: disable smartcard auth in sssd.conf
[pam]
pam_cert_auth = False

# Ensure sssd restarts on failure
sudo systemctl edit sssd.service
# Add under [Service]:
# Restart=on-failure
# RestartSec=5s
sudo systemctl daemon-reload
sudo systemctl restart sssd