CVE-2026-104033
Description
A flaw was found in SSSD. When configured to enforce account expiration using LDAP (Lightweight Directory Access Protocol) shadow attributes, SSSD fails to treat an expiration value of zero as an expired account. A user with valid credentials for an expired account can exploit this flaw to bypass access controls and authenticate to the system. This allows unauthorized access to persist after the account was intended to be deactivated.
Statement
This vulnerability is rated Moderate because it allows an expired LDAP account to authenticate without authorization, but exploitation requires pre-existing valid credentials and cannot lead to remote code execution or privilege escalation beyond the account's existing privileges. The flaw only affects environments explicitly configured to enforce shadow-based expiration through SSSD using LDAP access control policies. Systems utilizing default SSSD configurations, alternative expiration mechanisms, or centralized directory-level account lockouts are not vulnerable to this bypass.
Mitigation
Until a fix is available, deployments using SSSD's LDAP shadow-based expiration (access_provider = ldap with ldap_access_order including expire and ldap_account_expire_policy = shadow) should not rely on shadowExpire=0 to expire accounts. Set the shadowExpire attribute to a positive past day value so that SSSD correctly treats the account as expired, or enforce account disablement or expiration through directory-side controls that do not depend solely on this client-side SSSD check. If SSSD has cached the affected account's attributes, invalidate the cached entry (for example with sss_cache -u <username>) or restart the sssd service so the updated directory values take effect; note that restarting the service or clearing cached data can briefly interrupt active authentication sessions on the host.
Common Vulnerability Scoring System (CVSS) Score Details
Info alert:Important note
CVSS scores for open source components depend on vendor-specific factors (e.g. version or build chain). Therefore, Red Hat's score and impact rating can be different from NVD and other vendors. Red Hat remains the authoritative CVE Naming Authority (CNA) source for its products and services (see Red Hat classifications).
The following CVSS metrics and score provided are preliminary and subject to review.
CVSS v3 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 5.4 | N/A | 5.4 |
| Attack Vector | Network | N/A | Network |
| Attack Complexity | Low | N/A | Low |
| Privileges Required | Low | N/A | Low |
| User Interaction | None | N/A | None |
| Scope | Unchanged | N/A | Unchanged |
| Confidentiality | Low | N/A | Low |
| Integrity Impact | Low | N/A | Low |
| Availability Impact | None | N/A | None |
Vector
Red Hat: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N
cve.org: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N
Understanding the Weakness (CWE)
Availability
Technical Impact: DoS: Crash, Exit, or Restart; DoS: Resource Consumption (CPU); DoS: Resource Consumption (Memory); DoS: Instability
This weakness will generally lead to undefined behavior and therefore crashes. In the case of overflows involving loop index variables, the likelihood of infinite loops is also high.
Integrity
Technical Impact: Modify Memory
If the value in question is important to data (as opposed to flow), simple data corruption has occurred. Also, if the wrap around results in other conditions such as buffer overflows, further memory corruption may occur.
Confidentiality,Availability,Access Control
Technical Impact: Execute Unauthorized Code or Commands; Bypass Protection Mechanism
This weakness can sometimes trigger buffer overflows which can be used to execute arbitrary code. This is usually outside the scope of a program's implicit security policy.
Acknowledgements
This issue was discovered by Found by AISLE in partnership with Red Hat.
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