CVE-2026-80924 in Linux
Summary
by MITRE • 09/09/2026
In the Linux kernel, the following vulnerability has been resolved:
crypto: krb5 - use kfree_sensitive() for derived key buffers
crypto_krb5_prepare_encryption() and crypto_krb5_prepare_checksum() free the buffer holding the freshly derived keys with plain kfree(), leaving the key material behind in the freed slab object.
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Analysis
by VulDB Data Team • 09/09/2026
The Linux kernel cryptographic subsystem contains a memory management flaw within the Kerberos 5 encryption implementation that results in the exposure of sensitive cryptographic material to unauthorized processes or attackers who can access kernel heap memory. Specifically, the functions crypto_krb5_prepare_encryption and crypto_krb5_prepare_checksum are responsible for deriving keys used for data integrity and confidentiality during network authentication sessions. Upon completion of their tasks, these routines deallocate the memory buffers containing the derived keying material using the standard kfree function rather than a secure deletion routine. This oversight leaves residual copies of the secret keys in the freed slab cache objects, creating a window where sensitive information remains accessible until that specific memory region is reallocated and overwritten by subsequent kernel operations.
This vulnerability represents a classic instance of improper cleanup of sensitive data after use, which falls under CWE-243 Creation of Chroot Jail Without Correctly Setting Up Initial Working Directory in the broader context of security misconfiguration, but more accurately maps to CWE-798 Use of Hard-coded Credentials or CWE-312 Cleartext Storage of Sensitive Information when considering the persistence of secrets in memory. From an offensive perspective, this flaw aligns with ATT&CK technique T1005 Data from Local System as it enables potential attackers who have achieved local privilege escalation to extract cryptographic keys through kernel heap spraying or direct slab cache inspection tools like kmemleak or custom exploit modules that read freed memory regions. The impact is severe because Kerberos keys are often long-lived and used across multiple authentication sessions, meaning their exposure could compromise not only the current session but also past communications if replay attacks are feasible or future sessions if key reuse occurs within certain configurations.
The operational impact of this vulnerability extends beyond simple data leakage to include potential lateral movement and persistence in enterprise environments relying on Kerberos for centralized identity management. If an attacker gains low-privilege access to a system, they may exploit this flaw to dump kernel memory and extract active session keys or long-term service ticket encryption keys. These extracted credentials can then be used to impersonate legitimate users or services across the network without triggering traditional authentication alerts, effectively bypassing multi-factor protections that rely on password-based entry points. Furthermore, because Kerberos is foundational to many Windows Active Directory environments integrated with Linux systems via Samba or native clients, this vulnerability poses a significant risk to hybrid infrastructure security postures where cross-platform trust relationships are established.
Mitigation strategies primarily involve applying the latest kernel updates provided by distribution vendors that include patches replacing kfree with kfree_sensitive for all buffers holding derived cryptographic keys in the krb5 module. The kfree_sensitive function ensures that memory is zeroed out before being returned to the slab allocator, thereby preventing residual data from persisting in freed objects and reducing the attack surface for heap-based information disclosure exploits. In addition to patching system administrators should enforce strict kernel parameter restrictions such as disabling core dumps via /proc/sys/kernel/core_pattern or setting vm.mmap_min_addr to prevent user-space applications from mapping low memory addresses that might expose sensitive kernel structures. Regular auditing of kernel module usage and ensuring that only necessary cryptographic modules are loaded can further reduce the risk profile by limiting potential attack vectors associated with complex subsystems like Kerberos implementation details within the Linux crypto API framework.