CVE-2026-80913 in Linux
Summary
by MITRE • 09/04/2026
In the Linux kernel, the following vulnerability has been resolved:
selinux: require every boolean value to be defined
p_bools.nprim comes from the policy image independently of how many booleans follow it, and cond_index_bool() fills bool_val_to_struct[] at
value - 1, so a count larger than the values present leaves NULL entries. Every user of that array then walks it by index and dereferences each entry: cond_evaluate_expr() on the access-vector path, security_get_bools() and security_get_bool_value() behind selinuxfs, and security_set_bools(). A sparse class value is absorbed by policydb_class_isvalid() and its siblings; booleans have no such predicate, and no consumer that could use one.
Reject a boolean value that no boolean defines, once, where the array is built. Conforming policies define every boolean they declare and are unaffected.
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Analysis
by VulDB Data Team • 09/04/2026
The Linux Security Modules subsystem within the kernel contains a critical logic flaw in its SELinux policy parsing mechanism related to how boolean values are indexed and validated. The vulnerability stems from an inconsistency between the declared count of booleans in a security policy image and the actual number of defined boolean entries. Specifically, the variable p_bools.nprim indicates the total number of primary elements expected from the policy file, while the function cond_index_bool populates the bool_val_to_struct array using indices derived directly from these values minus one. If a policy declares more booleans than it actually defines, or if there is a mismatch in indexing logic, this process results in NULL pointers being stored at specific indices within the boolean value-to-structure mapping array. This creates an uninitialized pointer state that persists until explicitly accessed by various kernel functions responsible for evaluating security policies and managing SELinux states.
The operational impact of this flaw is severe because multiple core components of the SELinux subsystem blindly dereference entries in the bool_val_to_struct array without performing prior validation checks to ensure the entry is not NULL. Functions such as cond_evaluate_expr, which handles access-vector evaluation during policy enforcement, rely on these pointers to determine permission states. Similarly, user-space interactions via selinuxfs utilize security_get_bools and security_get_bool_value to retrieve current boolean settings, while security_set_bools allows modifications to these values. In all these cases, the code assumes that every index corresponding to a declared boolean will contain a valid structure pointer. When this assumption fails due to the aforementioned indexing error, any attempt to access an undefined or missing boolean entry results in a NULL pointer dereference. This typically manifests as a kernel panic or system crash, leading to a denial of service condition for systems relying on SELinux enforcement.
From a classification perspective, this vulnerability aligns with CWE-476, which describes a NULL Pointer Dereference issue arising from improper validation of user-controlled input or policy data structures. The root cause is effectively an out-of-bounds access where the code attempts to utilize memory locations that were never properly initialized due to logical errors in array population based on external policy definitions. In terms of attack vectors and tactical behavior, this flaw can be leveraged for local privilege escalation if a malicious user or compromised process with write access to SELinux boolean settings can trigger the evaluation path leading to the dereference. Alternatively, it serves as a reliable denial-of-service vector against any system running an improperly formatted policy image that exploits this indexing gap. The ATT&CK framework categorizes such kernel exploitation techniques under privilege escalation and impact categories, specifically highlighting how attackers target operating system components to disrupt availability or gain higher-level access through memory corruption errors.
The resolution implemented in the Linux kernel addresses this by introducing a validation check at the point where the bool_val_to_struct array is built. The fix ensures that every boolean value referenced during policy loading corresponds to an actually defined boolean entry, rejecting any policy image that attempts to reference undefined booleans. This approach enforces strict conformance with SELinux policy standards, ensuring that only well-formed policies are loaded into memory. Conforming security policies that correctly define all declared booleans remain unaffected by this change and continue to operate normally. For system administrators and developers, the mitigation involves updating to kernel versions where this validation is present and auditing custom or third-party SELinux policy modules for compliance with these stricter indexing requirements. This prevents the introduction of malformed state into the security module’s internal data structures, thereby eliminating the possibility of NULL pointer dereferences during runtime evaluation and management operations.