CVE-2026-23323: 
Linux Debian vulnerability analysis and mitigation

CVE-2026-23323 is an out-of-bounds write vulnerability in the Linux kernel's Apple Silicon SMC hardware monitoring driver (macsmc-hwmon). The driver contained two critical bugs: incorrect sensor array assignment causing out-of-bounds memory access, and flawed float conversion logic in macsmc_hwmon_write_f32(). Affected kernel versions include 6.19.1 through 6.19.6 and 7.0-rc1 through 7.0-rc7. It was disclosed on March 25, 2026, and carries a CVSS v3.1 base score of 7.8 (High) (Red Hat Advisory, Red Hat Bugzilla).

The vulnerability is classified as CWE-787 (Out-of-bounds Write) and stems from two distinct bugs in the macsmc-hwmon driver. First, the voltage sensor population loop used the wrong string prefix ("volt-" instead of "voltage-") and incorrectly assigned voltage sensors to the temperature sensor array (hwmon->temp.sensors) rather than the voltage sensor array (hwmon->volt.sensors), leading to out-of-bounds memory access or data corruption when both sensor types are present. Second, the macsmc_hwmon_write_f32() function contained flawed exponent logic for values >= 2^24 and lacked proper mantissa masking, potentially causing incorrect values to be written to the System Management Controller (SMC). Exploitation requires local access with low privileges on Apple Silicon systems running affected kernel versions (Red Hat Bugzilla, Kernel Patch 1).

Successful exploitation on affected Apple Silicon systems could result in memory corruption and system instability due to out-of-bounds writes during sensor enumeration, incorrect hardware sensor readings disrupting thermal management and fan control, and potential system crashes. The vulnerability is limited to systems running Linux on Apple Silicon hardware with the macsmc-hwmon driver active, and requires local low-privileged access, making it a concern primarily for multi-user systems and container environments where untrusted local users are present (Red Hat Advisory).

There is no known public proof-of-concept exploit and no evidence of in-the-wild exploitation at this time. The vulnerability is not listed in the CISA Known Exploited Vulnerabilities (KEV) catalog. The EPSS score is approximately 0.018% (0.000180), indicating a very low probability of exploitation in the near term (Red Hat Advisory).

Update the Linux kernel to version 6.19.7 or later (for systems on the 6.19.x branch), or to 7.0-rc3 or later (for systems on the 7.0 development branch). Patches are available in the stable kernel repositories at commits 5dd69b864911ae3847365e8bafe7854e79fbeecb and 625ef35b70d3883fb9a41cd5a988e64dd3e447d6. As a temporary workaround for systems that cannot be immediately updated, disabling the macsmc-hwmon driver (if not critical to operations) can mitigate the risk (Red Hat Bugzilla, Kernel Patch 1, Kernel Patch 2).