CVE-2026-53134
MediumCVSS 5.5Exploitation Probability (EPSS)
Low risk7th percentile — higher than 7% of all known CVEs
Summary
A vulnerability in the Linux kernel's netfilter nft_fib module causes a leak of uninitialized kernel stack data to userspace. The issue occurs when the OIFNAME result register is declared with IFNAMSIZ length but only one register is written on lookup failure, leaving three registers stale. Additionally, the NFTA_FIB_F_PRESENT flag was accepted for incorrect result types, also leading to data leaks.
Risk Assessment
An attacker could exploit this vulnerability to read uninitialized kernel stack data, potentially exposing sensitive system information or data from other processes. This could facilitate privilege escalation or bypass of security mechanisms.
Recommendation
Immediately update the Linux kernel to a version containing the fix (commit: 9b2c2e0c8c5e). If an update is not possible, restrict access to packet filtering using nft_fib and monitor the system for unusual behavior.
Original NVD description (English source)
In the Linux kernel, the following vulnerability has been resolved: netfilter: nft_fib: fix stale stack leak via the OIFNAME register For NFT_FIB_RESULT_OIFNAME the destination register is declared with len = IFNAMSIZ (four 32-bit registers), but on the lookup-fail, RTN_LOCAL and oif-mismatch paths nft_fib{4,6}_eval() only writes one register via "*dest = 0". The remaining three registers are left as whatever was on the stack in nft_do_chain()'s struct nft_regs, and a downstream expression that loads the register span can leak that uninitialised kernel stack to userspace. The NFTA_FIB_F_PRESENT existence check has the same shape: it is only meaningful for NFT_FIB_RESULT_OIF, yet it was accepted for any result type while the eval stores a single byte via nft_reg_store8(), leaving the rest of the declared span stale. Fix both: - replace the bare "*dest = 0" in the eval with nft_fib_store_result(), which strscpy_pad()s the whole IFNAMSIZ for OIFNAME (and is already used on the other early-return path), and - restrict NFTA_FIB_F_PRESENT to NFT_FIB_RESULT_OIF and declare its destination as a single u8, so the marked span matches the one byte the eval writes.