CVE-2026-53218

Description

In the Linux kernel, the following vulnerability has been resolved: netfilter: nft_exthdr: fix register tracking for F_PRESENT flag nft_exthdr_init() passes user-controlled priv->len to nft_parse_register_store(), which marks that many bytes in the register bitmap as initialized. However, when NFT_EXTHDR_F_PRESENT is set, the eval paths write only 1 byte (nft_reg_store8) or 4 bytes (*dest = 0 on TCP/DCCP error path). When len > 4, registers beyond the first are never written, retaining uninitialized stack data from nft_regs. Bail out if userspace requests too much data when F_PRESENT is set.

References

• https://git.kernel.org/stable/c/19748967d59c31d24d21d40b728570788310b237
• https://git.kernel.org/stable/c/46fc15a044e9938e7ea77786fb37edd2cd74f031
• https://git.kernel.org/stable/c/67b27434c43b68a97becda98c9f0c8cf6cba2134
• https://git.kernel.org/stable/c/772cecf198da732faebb5dcfc46d66a505be8495
• https://git.kernel.org/stable/c/78069a6d8bc86c9e036eb82c2af4a19cc1871a53