{"id":"CVE-2026-53267","title":"netfilter: nft_ct: bail out on template ct in get eval","summary":"In the Linux kernel, the following vulnerability has been resolved:\n\nnetfilter: nft_ct: bail out on template ct in get eval\n\nI noticed this issue while looking at a historic syzbot report [1].\n\nA rule like the one below is enough to trig…","severity":"high","cvss":7.8,"cvssVector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","cvssSource":"cna","vendor":"Linux","product":"Linux","affected":["Linux >= 45d9bcda21f4c13be75e3571b0f0ef39e77934b5 < af80f78ce984649e1698b841cd33f4fa505ad828","Linux >= 45d9bcda21f4c13be75e3571b0f0ef39e77934b5 < 8470f676eadeab99132708acb1a85915664d6115","Linux >= 45d9bcda21f4c13be75e3571b0f0ef39e77934b5 < f071b0bf078146368d18e4eec386bf2ddc0ab7e0","Linux >= 45d9bcda21f4c13be75e3571b0f0ef39e77934b5 < 2e154b5f53f1b0b490c7b8b02499f90feb86b1d5","Linux >= 45d9bcda21f4c13be75e3571b0f0ef39e77934b5 < 3027ecbdb5fdf9200251c21d4818e4c447ef78e1","Linux 4.1"],"ssvc":{"exploitation":"none","automatable":"no","technicalImpact":"total","timestamp":"2026-10-16T15:28:07.142807Z"},"published":"2026-06-25","updated":"2026-10-16","sourceUpdated":"2026-10-16T15:31:44.472Z","source":"CVEORG","sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2026-53267","references":[{"url":"https://git.kernel.org/stable/c/af80f78ce984649e1698b841cd33f4fa505ad828"},{"url":"https://git.kernel.org/stable/c/8470f676eadeab99132708acb1a85915664d6115"},{"url":"https://git.kernel.org/stable/c/f071b0bf078146368d18e4eec386bf2ddc0ab7e0"},{"url":"https://git.kernel.org/stable/c/2e154b5f53f1b0b490c7b8b02499f90feb86b1d5"},{"url":"https://git.kernel.org/stable/c/3027ecbdb5fdf9200251c21d4818e4c447ef78e1"}],"tags":["cve.org"],"epss":0.0012,"epssPercentile":0.01678,"ingestedAt":"2026-10-16T17:24:46.740Z","slug":"CVE-2026-53267","body":"## Overview\n\nIn the Linux kernel, the following vulnerability has been resolved:\n\nnetfilter: nft_ct: bail out on template ct in get eval\n\nI noticed this issue while looking at a historic syzbot report [1].\n\nA rule like the one below is enough to trigger the bug:\n\n    table ip t {\n        chain pre {\n            type filter hook prerouting priority raw;\n            ct zone set 1\n            ct original saddr 1.2.3.4 accept\n        }\n    }\n\nThe first expression attaches a per-cpu template ct via\nnft_ct_set_zone_eval() (nf_ct_tmpl_alloc -> kzalloc, tuple is all\nzero, nf_ct_l3num(ct) == 0). The next expression then calls\nnft_ct_get_eval() on the same skb, treats the template as a real ct\nand hits the 16-byte memcpy path. With dreg at NFT_REG32_15 this\noverflows past struct nft_regs on the kernel stack; with smaller\ndreg values it silently clobbers adjacent registers.\n\nReject template ct at the eval entry and in nft_ct_get_fast_eval(),\nmirroring the check nft_ct_set_eval() already has. Additionally,\nbound the address copy in NFT_CT_SRC / NFT_CT_DST by priv->len\ninstead of by nf_ct_l3num(ct): nf_ct_get_tuple() zeroes the tuple\nbefore pkt_to_tuple() fills in only the protocol-relevant leading\nbytes, so the trailing bytes of tuple->{src,dst}.u3.all are\nwell-defined zero. priv->len is validated at rule load, so the\ncopy size is now bounded by the destination register rather than\nby an untrusted field on the conntrack.\n\n[1]: https://syzkaller.appspot.com/bug?id=389cf09cb72926114fce90dc85a2c3231dcb647c\n\n## Affected\n\n- `Linux >= 45d9bcda21f4c13be75e3571b0f0ef39e77934b5 < af80f78ce984649e1698b841cd33f4fa505ad828`\n- `Linux >= 45d9bcda21f4c13be75e3571b0f0ef39e77934b5 < 8470f676eadeab99132708acb1a85915664d6115`\n- `Linux >= 45d9bcda21f4c13be75e3571b0f0ef39e77934b5 < f071b0bf078146368d18e4eec386bf2ddc0ab7e0`\n- `Linux >= 45d9bcda21f4c13be75e3571b0f0ef39e77934b5 < 2e154b5f53f1b0b490c7b8b02499f90feb86b1d5`\n- `Linux >= 45d9bcda21f4c13be75e3571b0f0ef39e77934b5 < 3027ecbdb5fdf9200251c21d4818e4c447ef78e1`\n- `Linux 4.1`\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.","depth":"twilight","depthScore":43,"depthScoreParts":{"impact":42.9,"likelihood":0,"exploitation":0,"ransomware":0},"changes":[]}