CVE-2026-89718

Received Received - Intake

Out-of-Bounds Access in Linux Kernel zram

Publication date: 2026-09-11

Last updated on: 2026-09-11

Assigner: kernel.org

Description

In the Linux kernel, the following vulnerability has been resolved: zram: fix out-of-bounds access in writeback_store() Patch series "zram: fix stale scan bounds after reinitialization". Both writeback_store() and read_block_state() derive their table scan bounds from zram->disksize before acquiring dev_lock. If the device is reset and reinitialized with a smaller disksize between that read and lock acquisition, the bound can describe the old table while the scan operates on the new one. This can lead to out-of-bounds slot accesses. Move both bound calculations under dev_lock so each bound remains consistent with the table throughout its scan. Keep the fixes separate because the affected interfaces originate from different commits and can be backported independently. This patch (of 2): writeback_store() calculates the table scan bounds before taking dev_lock. A reset followed by reconfiguration with a smaller disksize can therefore replace zram->table while writeback_store() is waiting for the lock. Once it acquires the lock, it sees an initialized device but scans the new table using the old upper bound, resulting in an out-of-bounds access. Calculate the number of pages while holding dev_lock so the scan bound matches the table protected by the lock.

CVSS Scores

EPSS Scores

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Meta Information

Published

2026-09-11

Last Modified

2026-09-11

Generated

2026-09-12

AI Q&A

2026-09-12

EPSS Evaluated

N/A

NVD

CVE-2026-89718

EUVD

EUVD-2026-76630

Affected Vendors & Products

Vendor	Product	Version / Range
linux	linux_kernel	*

Helpful Resources

Exploitability

CWE

KEV

CWE ID	Description
CWE-UNKNOWN

Attack-Flow Graph

Executive Summary

This vulnerability is in the Linux kernel's zram module. It involves an out-of-bounds memory access in the writeback_store() function. The issue occurs when the device is reset and reinitialized with a smaller size while the function is waiting to acquire a lock. This causes the function to use an outdated table size for scanning, leading to potential memory corruption or crashes.

Detection Guidance

This vulnerability is specific to the Linux kernel's zram module and requires kernel-level inspection. Detect it by checking kernel logs for out-of-bounds access errors or crashes related to zram. Use commands like 'dmesg | grep zram' or 'journalctl -k | grep zram' to review kernel messages. Ensure your kernel version is patched or updated to a version containing the fix.

Impact Analysis

If exploited, this vulnerability could allow an attacker to cause a denial-of-service (system crash) or potentially execute arbitrary code with kernel privileges. It affects systems using zram for compressed swap or storage, which are common in Linux environments.

Mitigation Strategies

Immediately update your Linux kernel to a patched version that includes the fix for CVE-2026-89718. If updating is not immediately possible, avoid resetting and reinitializing zram devices with smaller disksizes until the patch is applied. Monitor kernel logs for any signs of exploitation or crashes.

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