CVE-2026-53016: Linux Kernel CCP Buffer Overflow – Local Privilege Escalation

Technical summary

CVE-2026-53016 is a buffer overflow in the Linux kernel's CCP cryptographic driver (drivers/crypto/ccp/). The vulnerability occurs in the ccp_aes_complete() function when handling AES-CTR requests with RFC3686 parameters submitted through AF_ALG (Algorithm socket family). RFC3686-CTR specifies an 8-byte IV, but ccp_aes_complete() restores AES_BLOCK_SIZE (16 bytes) into the caller's IV buffer, overflowing it by 8 bytes. The fix involves calling crypto_skcipher_ivsize() to determine and use the algorithm's actual IV length rather than hardcoding the block size. This is classified as a CWE-787 (Out-of-bounds Write) and CWE-805 (Buffer Access with Incorrect Length Value).

Business impact

Local privilege escalation and denial of service are the primary business risks. An authenticated local user can trigger this overflow to corrupt kernel memory, potentially gaining root privileges or causing system crashes that disrupt availability. Containerized environments and multi-tenant systems face elevated risk, as any container or user namespace with access to the crypto API could mount an attack. The impact extends to any Linux system running vulnerable kernel versions where CCP crypto acceleration is in use, particularly in cloud, edge, and specialized computing environments relying on AMD processors.

Affected systems

This vulnerability affects the Linux kernel across all versions shipping the CCP crypto driver without the fix. The vulnerability is specific to systems using AF_ALG with RFC3686-CTR-AES via the CCP driver, which is primarily enabled on AMD-based systems. Systems not using the CCP driver, systems with CCP disabled, or systems not submitting RFC3686 requests are unaffected. Check if your kernel is compiled with CONFIG_CRYPTO_DEV_CCP or CONFIG_CRYPTO_DEV_CCP_DD enabled and if userspace applications use AF_ALG crypto sockets.

Exploitability

Exploitation requires local access and prior authentication (the vector requires PR:L). No network-based attack is possible. An attacker with shell access or a containerized application can craft RFC3686-CTR-AES requests via AF_ALG to trigger the overflow. The vulnerability is deterministic and highly reliable once access is achieved. However, the requirement for local privilege context prevents remote exploitation. The lack of CISA KEV listing suggests active exploitation in the wild is not yet documented, though the vulnerability is trivial to trigger once access is obtained.

Remediation

Apply a kernel patch that modifies ccp_aes_complete() to call crypto_skcipher_ivsize() and copy only the algorithm's IV length instead of AES_BLOCK_SIZE. Vendors have begun releasing patched versions; verify against your distribution's security advisories for specific kernel versions. Short-term mitigation includes disabling the CCP crypto driver (CONFIG_CRYPTO_DEV_CCP=n) if not actively required, or restricting AF_ALG access via AppArmor, SELinux, or seccomp policies. Long-term, upgrade to a patched kernel once available for your platform.

Patch guidance

Monitor your Linux distribution's security advisories for patched kernel versions addressing CVE-2026-53016. Patches typically involve a single-line or multi-line change to ccp_aes_complete() in the CCP driver. Verify the patch against upstream kernel repositories or vendor advisories before deployment. Test in a non-production environment first, particularly if custom kernel modules or specialized crypto workloads are in use. Apply through your standard change management process; kernel updates typically require a reboot.

Detection guidance

Monitor kernel logs for segmentation faults, memory corruption warnings, or audit logs showing AF_ALG crypto requests. Systems logging crypto_skcipher operations or CCP driver messages may show anomalies preceding a crash. Intrusion detection systems can flag repeated AF_ALG socket creation patterns or unusual crypto API syscall sequences. However, memory corruption may be silent; rely primarily on patch deployment and version verification rather than behavioral detection. Verify kernel version with `uname -r` and check CCP driver availability with `lsmod | grep ccp`.

Why prioritize this

This is a HIGH-severity local privilege escalation affecting all authenticated users. While not actively exploited at scale (KEV status: false), the vulnerability is trivial to trigger and provides direct kernel access to local attackers. Containerized and cloud workloads should prioritize patching. Organizations with strict local access controls or environments not using CCP can defer slightly, but upstream and end-of-life kernels pose risk. Given the June 2026 publication date, rapid patch availability from vendors is likely.

Risk score, explained

CVSS 3.1 score of 7.8 (HIGH) reflects: local attack vector (AV:L), low complexity (AC:L), low privilege requirement (PR:L), no user interaction needed (UI:N), and impact limited to a single system (S:U). High confidentiality, integrity, and availability impacts (C:H/I:H/A:H) account for kernel memory corruption enabling privilege escalation or DoS. The score appropriately captures the severity for local attackers while excluding remote vectors.

Frequently asked questions