The Linux kernel contains a flaw in the handling of High‑Availability Seamless Redundancy (HSR) supervision frames. The code fails to fully linearize the entire Type‑Length‑Value (TLV) header before accessing it, so a truncated frame can force an out‑of‑bounds read of kernel memory. This out‑of‑bounds read may expose sensitive kernel data to an attacker. The weakness is classified as CWE‑805: Out‑of‑Bounds Read. No evidence of remote code execution is provided; the impact is limited to data leakage.

All Linux kernel releases that implement the HSR interface and do not contain the recent commit are affected. Any system that parses HSR supervision frames—whether running the mainline kernel or a branch kernel—remains vulnerable until the patch is applied. Exact version ranges are not documented in the advisory, so all kernels capable of HSR operation should be examined for the presence of the fix.

The CVSS score of 9.8 indicates a critical severity. The EPSS score of less than 1% suggests that exploitation is currently rare. The description infers that an attacker with network access can craft a malicious HSR frame and send it to the target over an untrusted network, leveraging the unprivileged kernel path that processes supervision frames. The vulnerability is not listed in the CISA KEV catalog. Even though there is no documented privilege escalation, the data leakage could aid further attacks.