CISA Adds Three Actively Exploited Linux Kernel Vulnerabilities to KEV Catalog
The U.S. Cybersecurity and Infrastructure Security Agency (CISA) has added three vulnerabilities in the Linux Kernel to its Known Exploited Vulnerabilities (KEV) catalog, confirming that the flaws are being actively exploited.
On 18 September 2026, CISA updated the catalog with CVE-2025-39682, CVE-2026-53266, and CVE-2025-39964. Federal civilian agencies are required to remediate the issues within the mandated timeframe and to investigate systems for signs of compromise.
CVE-2025-39682 – kTLS Zero-Length Record Handling
The first vulnerability resides in the kernel TLS implementation known as kTLS. A specially crafted TLS record with zero length is not processed correctly, allowing subsequent records to be interpreted under incorrect assumptions. This flaw can be triggered over the network and may result in memory corruption.
CVE-2026-53266 – ebtables Out-of-Bounds Write
The second issue affects the ebtables packet-filtering framework used for network bridging. When rewriting the source MAC address of ARP packets, an out-of-bounds write occurs, potentially allowing an attacker to corrupt kernel memory and escalate privileges.
CVE-2025-39964 – AF_ALG Race Condition
The third vulnerability is located in the AF_ALG interface that exposes cryptographic algorithms to user space. A race condition arises when multiple concurrent writes are performed on the same socket, leading to data mixing and inconsistent internal socket state that can be abused by local attackers.
CISA continues to urge organizations to apply available patches and monitor for exploitation attempts against these Linux Kernel components.
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