CVE-2026-53038 Linux CVE debrief

Who should care

Linux kernel users and administrators should be aware of this vulnerability, as it could potentially allow for security bypass. Users with TPM chips supporting algorithms not yet in tpm_algorithms are particularly affected.

Technical summary

The Linux kernel vulnerability CVE-2026-53038 is caused by the improper handling of unsupported hash algorithms in the ima_fs component. When a TPM algorithm is not supported, ima_tpm_chip->allocated_banks[i].crypto_id is set to HASH_ALGO__LAST. However, this value is then used to access hash_algo_name[], leading to an out-of-bounds read. The issue arises because the TPM chip supports algorithms like sha3_256, which is not yet recognized in tpm_algorithms. The fix involves creating securityfs files with a '_tpm_alg_<ID>' postfix for unsupported algorithms.

Defensive priority

Medium

Recommended defensive actions

• Inventory Linux systems using TPM chips with potentially unsupported algorithms.
• Verify kernel version and update if necessary.
• Monitor for unusual activity in securityfs files.
• Implement compensating controls for ima_fs.
• Review the supplied official advisory or CVE record to validate affected scope, severity, and vendor guidance.
• Plan vendor-supported updates or mitigations through normal change control where exposure is confirmed.
• Check relevant monitoring, detection, and logs for exposed assets that need extra review.

Evidence notes

The vulnerability was discovered in the Linux kernel's ima_fs component. An out-of-bounds read occurs in hash_algo_name due to improper handling of unsupported TPM algorithms. The issue was resolved by creating securityfs files with a '_tpm_alg_<ID>' postfix for unsupported algorithms. Limited information is available about potential exploits or attacks.

Official resources