CVE-2026-87853

In SSSD configured with the LDAP access provider and ldap_access_order including ppolicy or lockout, a fail-open condition in the LDAP ppolicy access check can occur if a user lookup returns zero results. This can incorrectly return success and cache an allow decision, permitting continued authorization for a deleted or deprovisioned user.

A flaw was found in sssd where a local unprivileged user can send a specially crafted request with a zero-length body to the NSS responder. This can lead to instability or termination of the NSS responder, causing denial of service.

A flaw was found in SSSD where a local attacker with privileges to connect to the PAM responder socket can send a specially crafted protocol request. If `pam_app_services` is enabled and the service item is omitted, a NULL pointer dereference can occur, crashing the PAM responder and disrupting authentication services.

A flaw was found in sssd in the PAM responder's protocol v1 parser, pam_parse_in_data(). A local client with access to the PAM responder's UNIX socket can exploit this by negotiating protocol v1 and sending an empty or truncated PAM request body, triggering an out-of-bounds read that may cause the PAM responder to terminate or restart, leading to a local denial of service.

A flaw was found in the sssd NSS responder. This input validation vulnerability allows a local attacker, by sending specially crafted service lookup requests to the NSS responder's UNIX socket, to cause an out-of-bounds read. This may lead to a denial of service by crashing the NSS responder process.

A flaw was found in SSSD. The extract_authtok_v1() function in the PAM responder does not validate the auth_token_length field against the remaining buffer size before processing. A local attacker can exploit this via a crafted protocol v1 request to the PAM responder socket, causing an out-of-bounds read and process crash, resulting in a denial of service.

A flaw was found in SSSD. The sss_nss_protocol_fill_initgr() function in the NSS responder pre-allocates reply space for all group entries but does not shrink the packet when groups are skipped, causing uninitialized heap bytes to be transmitted to the client. A local attacker can exploit this to disclose cached directory data and heap layout information from the sssd_nss process.

In SSSD, the sss_nss_protocol_parse_addr() function in the NSS responder does not validate the addrlen field against the packet size. A local attacker can send a crafted GETHOSTBYADDR request, causing an out-of-bounds read and process crash (DoS).

A path traversal vulnerability was found in SSSD's AD GPO provider. The ad_gpo_extract_smb_components() function does not sanitize .. sequences in the gPCFileSysPath LDAP attribute, allowing an attacker with AD GPO management access to write files outside the GPO cache directory as root. On default RHEL configurations with SELinux enforcing, this can be used to inject Kerberos configuration leading to authentication bypass.

A flaw was found in SSSD's LDAP sudo provider. When the ldap_sudo_search_base option is not explicitly configured, SSSD searches the entire LDAP directory tree for sudoRole objects. An authenticated attacker with write access to any subtree can inject a sudoRole object granting root-level sudo privileges on all SSSD-enrolled hosts.