CVE-2026-53134

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.

Affected Software

References

• https://git.kernel.org/stable/c/3544210609f6d1db282bbdeca639104ef624c393
• https://git.kernel.org/stable/c/6744e49fe51bfba26522acc2d0e9703cb41d8e50
• https://git.kernel.org/stable/c/84d8f58cf28a0415413f43ba7148f7bacd4c1b6e
• https://git.kernel.org/stable/c/8c84885e9790823828bb8084736ea15769b1ac16
• https://git.kernel.org/stable/c/ab185e0c4fb82dfba6fb86f8271e06f931d9c64c
• https://git.kernel.org/stable/c/d19ddef8c327a4773ff81f8e51027d1e0b4cf069
• https://git.kernel.org/stable/c/eb8a8124484dbc3c2b543e207da39bbccb703d31
• https://git.kernel.org/stable/c/eca18feed38b3377a2ec5d1f22af1170c55d0171