CVE-2026-80731
HighCVSS 7.8Exploitation Probability (EPSS)
Low risk8th percentile - higher than 8% of all known CVEs
Summary
A vulnerability was found in the Linux kernel's dev_validate_header() function in the networking stack. For processes with CAP_SYS_RAWIO capability, it zero-padded short link-layer headers by reading dev->hard_header_len directly. If the device was reconfigured and this value increased in the meantime, the zeroing write went beyond the allocated buffer, causing an out-of-bounds write.
Risk Assessment
The vulnerability may lead to an out-of-bounds memory write in the kernel, potentially causing a system crash or privilege escalation. However, exploitation requires CAP_SYS_RAWIO capability, which limits its practical use.
Recommendation
Apply the official Linux kernel patch that removes the zero-padding branch for CAP_SYS_RAWIO immediately. After updating, reboot the system to load the new kernel.
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Original NVD description (English source)
In the Linux kernel, the following vulnerability has been resolved: net: remove CAP_SYS_RAWIO zero-padding in dev_validate_header dev_validate_header() reads dev->hard_header_len directly when zero-padding short link layer headers for CAP_SYS_RAWIO holders: if (capable(CAP_SYS_RAWIO)) { memset(ll_header + len, 0, dev->hard_header_len - len); return true; } Packet send paths call dev_validate_header() on skbs whose headroom was allocated from an earlier hard_header_len read. If the device is reconfigured so that dev->hard_header_len increases before validation, the memset writes past the reserved buffer, an out-of-bounds write. This out-of-bounds write is masked in some SOCK_RAW paths today because the same concurrent increase can first make skb_push() exceed the reserved headroom and trigger skb_under_panic(). Remove the zero-padding branch before making those hard_header_len reads consistent, so the snapshot fixes do not turn a loud panic into a silent overwrite. This path is only reached for variable length L2 protocols, where len < hard_header_len but len >= min_header_len. No remaining in-tree variable length L2 protocol implements header_ops->validate, and the CAP_SYS_RAWIO bypass that zero-pads and accepts short headers has no real value beyond allowing testing of intentionally malformed input. Drop the CAP_SYS_RAWIO branch. The remaining reads of dev->hard_header_len in dev_validate_header() are comparisons only and have no memory safety impact.
Vulnerability data from NVD (NIST) · CISA KEV · EPSS