CVE-2026-93146 in Linux
Summary
by MITRE • 09/18/2026
In the Linux kernel, the following vulnerability has been resolved:
time/namespace: Validate nanosecond field in proc_timens_set_offset()
The function validates tv_sec to be within [-KTIME_SEC_MAX, KTIME_SEC_MAX]
but never validates that tv_nsec is within the valid range of [0, NSEC_PER_SEC-1] before using it in timespec64_add().
timespec64_add() expects both timespec64 structures to have normalized values with tv_nsec in the range [0, 999999999]. If off->val.tv_nsec
contains invalid values (negative or >= NSEC_PER_SEC), it could lead to incorrect calculations or unexpected behavior.
Add validation to ensure tv_nsec is within the valid range before performing the addition.
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Analysis
by VulDB Data Team • 09/18/2026
The Linux kernel's time namespace implementation contains a critical input validation deficiency in the proc_timens_set_offset function, which serves as an interface for configuring time offsets within isolated namespaces. This vulnerability stems from an incomplete boundary check where the code verifies that the seconds component of the timespec64 structure falls within acceptable limits defined by KTIME_SEC_MAX but fails to validate the nanoseconds component against its valid range of zero to NSEC_PER_SEC minus one. By neglecting this specific validation step, the kernel allows user-space applications to supply malformed time offset values that violate internal structural invariants required for correct arithmetic operations on time structures.
The technical flaw manifests when these invalid nanosecond values are passed directly into timespec64_add without normalization or range checking. This function assumes both input structures contain normalized values where the nanoseconds field is strictly between zero and nine hundred ninety-nine million, nine hundred ninety-nine thousand, nine hundred ninety-nine. When a negative value or a value exceeding this maximum threshold is provided, the arithmetic operation produces incorrect results rather than raising an error or normalizing the data automatically. This deviation from expected behavior can lead to unpredictable system states within time namespaces, potentially causing processes to observe erroneous timestamps that disrupt scheduling, logging, and synchronization mechanisms dependent on accurate temporal data.
From a security perspective, this issue is classified under CWE-20 Improper Input Validation as it involves failing to verify the integrity of user-supplied input before processing. The attack vector aligns with ATT&CK technique T1530 Data from Information Repositories or potentially T1497 Virtualization/Sandbox Evasion if exploited in a containerized environment, although its primary classification is an improper validation leading to logic errors rather than direct code execution. An attacker could exploit this by crafting specific syscalls that set time namespace offsets with out-of-bounds nanosecond values, thereby inducing logical inconsistencies within the kernel's time management subsystem. While immediate exploitation for privilege escalation may be complex due to the nature of the resulting incorrect calculations, such flaws can contribute to denial of service conditions or serve as building blocks in more sophisticated attacks targeting timing-based security controls.
The resolution involves implementing explicit range checks on the tv_nsec field prior to its use in arithmetic operations. By ensuring that only values within the canonical range are accepted, the kernel maintains internal consistency and prevents undefined behavior arising from malformed inputs. This fix reinforces the principle of defense in depth by validating input at the boundary where it enters the trusted computing base. System administrators should ensure their kernels are updated with this patch to maintain the integrity of time-sensitive operations across all namespaces. Developers integrating similar functionality must adhere strictly to structural constraints defined by kernel APIs, verifying both major and minor components of composite data structures before performing mathematical transformations that rely on normalized inputs.