CVE-2025-68726: 
Linux Debian vulnerability analysis and mitigation

CVE-2025-68726 is a memory corruption vulnerability in the Linux kernel's cryptographic framework, specifically affecting the handling of reqsize in AEAD (Authenticated Encryption with Associated Data) algorithms. The flaw was introduced when commit afddce13ce81d added the cra_reqsize field to the crypto_alg struct as a replacement for type-specific reqsize fields, but the underlying AEAD framework functions were never updated to properly initialize reqsize from this new field. This causes memory corruptions and kernel crashes when AEAD algorithms use cra_reqsize instead of the proper crypto_*_set_reqsize() calls. The vulnerability was disclosed on December 24, 2025, and affects Linux kernel versions from commit afddce13ce81d up to the patched releases. Feedly estimates this as a Medium severity issue with an EPSS score of 0.00017 (Red Hat CVE, Red Hat Bugzilla).

The root cause is improper initialization of the reqsize field in the AEAD algorithm framework (CWE-665: Improper Initialization). When commit afddce13ce81d introduced cra_reqsize to crypto_alg, it was designed for ahash and acomp algorithm types, but was subsequently recommended for use across all crypto algorithm types. AEAD algorithm drivers that adopted cra_reqsize instead of calling crypto_aead_set_reqsize() triggered memory corruption because the AEAD init path did not read cra_reqsize to set the request context size, leading to undersized memory allocations for crypto requests. The fix adds proper set_reqsize calls in the AEAD init function to correctly propagate cra_reqsize into the framework. A detailed crash reproduction is documented at the reporter's GitHub gist (Red Hat CVE).

Exploitation of this vulnerability can result in kernel memory corruption and system crashes (denial of service) on Linux systems that use AEAD cryptographic algorithms. Because the corruption occurs in kernel memory during cryptographic request processing, it could potentially be leveraged for privilege escalation or arbitrary code execution in the kernel context, though no such exploitation has been demonstrated. Systems heavily relying on AEAD-based cryptography (e.g., IPsec, TLS offload, disk encryption) are most at risk of instability (Red Hat CVE).

There is no public proof-of-concept exploit and no evidence of in-the-wild exploitation as of the time of disclosure. The EPSS score is very low at 0.00017, reflecting the limited likelihood of near-term exploitation. The vulnerability is not listed in the CISA Known Exploited Vulnerabilities (KEV) catalog. Triggering the bug requires the ability to invoke AEAD cryptographic operations on an affected kernel, which typically requires local access or a privileged context (Red Hat CVE).

Patches are available for multiple Linux kernel stable branches. The fix has been applied in kernel versions 6.17.13, 6.18.2, and 6.19-rc1 via commits 64377e66e187, 9b04d8f00569, and 12b413f5460c respectively. Administrators should update to the latest patched kernel version for their distribution. As a temporary measure, systems that do not require AEAD-based cryptographic operations may disable or avoid loading affected AEAD algorithm modules. Monitor system logs for kernel panics or memory corruption errors related to crypto subsystem activity (Red Hat CVE, Kernel Patch 6.18.2, Kernel Patch 6.17.13).