CVE-2026-15813: 
Linux Red Hat vulnerability analysis and mitigation

CVE-2026-15813 is an out-of-bounds write vulnerability in the network packet de-fragmentation engine of kronosnet (versions <= 1.34). The internal reassembly code fails to properly validate sequence numbers of incoming payload fragments, allowing a remote attacker to trigger memory corruption or heap corruption by sending malformed packets with corrupted sequence parameters. It was reported on July 15, 2026, and published to the NVD and GitHub Advisory Database on July 20, 2026. Affected products include kronosnet and Red Hat Enterprise Linux (RHEL/RHCOS) distributions that bundle it. It carries a CVSS v3.1 base score of 6.5 (Medium/High) (Red Hat CVE, GitHub Advisory).

The root cause is classified as CWE-787 (Out-of-bounds Write). Kronosnet's defragmentation subsystem tracks reassembled payload chunks using sequence numbers, but lacks rigorous boundary validation when ordering incoming fragments. A network-adjacent or remote attacker with no privileges or user interaction required can craft and inject fragments with overlapping, out-of-order, or invalid sequence numbers; when the parser attempts to reassemble the payload using these deceptive offsets, it writes data beyond the bounds of the allocated reassembly buffer, causing heap corruption or out-of-bounds memory access. Exploitation requires high attack complexity, as specific heap layout conditions must be met (Red Hat Bugzilla, GitHub Advisory).

Successful exploitation can cause sudden application crashes or system instability in the kronosnet daemon, resulting in a Denial of Service (DoS) condition. Depending on heap layout and the data overwritten during corruption, there is a potential — though not guaranteed — path to arbitrary code execution within the daemon's context, which could affect the integrity of the host system. Confidentiality impact is assessed as none, while integrity impact is low and availability impact is high (Red Hat Bugzilla, GitHub Advisory).

The vulnerability affects kronosnet versions <= 1.34; upgrading to a version beyond 1.34 is the recommended remediation. Red Hat has acknowledged the issue and a patch is tracked via Bugzilla (Bug 2500854); users of Red Hat Enterprise Linux and RHCOS should monitor Red Hat security advisories for updated packages. No specific configuration-based workaround has been published; restricting network access to kronosnet-exposed interfaces can reduce exposure until a patch is applied (Red Hat Bugzilla, Red Hat CVE).