{"id":"CVE-2026-31649","revision":"04c8785259b744368d3c54449a42174c","records":[{"revision":"04c8785259b744368d3c54449a42174c","observedAt":"2026-10-23T15:48:27.903+00:00","statement":{"source":"cve-program","id":"CVE-2026-31649","aliases":[],"title":"net: stmmac: fix integer underflow in chain mode","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nnet: stmmac: fix integer underflow in chain mode\n\nThe jumbo_frm() chain-mode implementation unconditionally computes\n\n    len = nopaged_len - bmax;\n\nwhere nopaged_len = skb_headlen(skb) (linear bytes only) and bmax is\nBUF_SIZE_8KiB or BUF_SIZE_2KiB.  However, the caller stmmac_xmit()\ndecides to invoke jumbo_frm() based on skb->len (total length including\npage fragments):\n\n    is_jumbo = stmmac_is_jumbo_frm(priv, skb->len, enh_desc);\n\nWhen a packet has a small linear portion (nopaged_len <= bmax) but a\nlarge total length due to page fragments (skb->len > bmax), the\nsubtraction wraps as an unsigned integer, producing a huge len value\n(~0xFFFFxxxx).  This causes the while (len != 0) loop to execute\nhundreds of thousands of iterations, passing skb->data + bmax * i\npointers far beyond the skb buffer to dma_map_single().  On IOMMU-less\nSoCs (the typical deployment for stmmac), this maps arbitrary kernel\nmemory to the DMA engine, constituting a kernel memory disclosure and\npotential memory corruption from hardware.\n\nFix this by introducing a buf_len local variable clamped to\nmin(nopaged_len, bmax).  Computing len = nopaged_len - buf_len is then\nalways safe: it is zero when the linear portion fits within a single\ndescriptor, causing the while (len != 0) loop to be skipped naturally,\nand the fragment loop in stmmac_xmit() handles page fragments afterward.","state":0,"publishedAt":"2026-04-24T14:45:02.52+00:00","modifiedAt":"2026-10-19T18:56:01.547+00:00","affected":[{"ecosystem":"Vendor product","name":"Linux","ranges":[],"versions":[],"rawVersionEvidence":"{\n                    \"product\": \"Linux\",\n                    \"vendor\": \"Linux\",\n                    \"defaultStatus\": \"unaffected\",\n                    \"repo\": \"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\n                    \"programFiles\": [\n                        \"drivers/net/ethernet/stmicro/stmmac/chain_mode.c\"\n                    ],\n                    \"versions\": [\n                        {\n                            \"version\": \"286a837217204b1ef105e3a554d0757e4fdfaac1\",\n                            \"lessThan\": \"513e06735f5be575b409d195822195348b164e48\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"286a837217204b1ef105e3a554d0757e4fdfaac1\",\n                            \"lessThan\": \"275bdf762e82082f064e60a92448fa2ac43cf95b\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"286a837217204b1ef105e3a554d0757e4fdfaac1\",\n                            \"lessThan\": \"a2b68a9a476b9544ff31f1fbcd5d80867a8a5e2f\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"286a837217204b1ef105e3a554d0757e4fdfaac1\",\n                            \"lessThan\": \"b7b8012193fd98236d7ae05d4b553f010a77b2ef\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"286a837217204b1ef105e3a554d0757e4fdfaac1\",\n                            \"lessThan\": \"2c91b39912278d0878f9ba60ba04d2518b18a08d\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"286a837217204b1ef105e3a554d0757e4fdfaac1\",\n                            \"lessThan\": \"6fca757c20396dc2e604dcc61922264e9e3dc803\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"286a837217204b1ef105e3a554d0757e4fdfaac1\",\n                            \"lessThan\": \"10d12b9240ebf96c785f0e2e4228318cd5f3a3eb\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"286a837217204b1ef105e3a554d0757e4fdfaac1\",\n                            \"lessThan\": \"51f4e090b9f87b40c21b6daadb5c06e6c0a07b67\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        }\n                    ]\n                }"},{"ecosystem":"Vendor product","name":"Linux","ranges":[],"versions":[],"rawVersionEvidence":"{\n                    \"product\": \"Linux\",\n                    \"vendor\": \"Linux\",\n                    \"defaultStatus\": \"affected\",\n                    \"repo\": \"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\n                    \"programFiles\": [\n                        \"drivers/net/ethernet/stmicro/stmmac/chain_mode.c\"\n                    ],\n                    \"versions\": [\n                        {\n                            \"version\": \"3.2\",\n                            \"status\": \"affected\"\n                        },\n                        {\n                            \"version\": \"0\",\n                            \"lessThan\": \"3.2\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"5.10.253\",\n                            \"lessThanOrEqual\": \"5.10.*\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"5.15.203\",\n                            \"lessThanOrEqual\": \"5.15.*\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"6.1.169\",\n                            \"lessThanOrEqual\": \"6.1.*\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"6.6.135\",\n                            \"lessThanOrEqual\": \"6.6.*\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"6.12.82\",\n                            \"lessThanOrEqual\": \"6.12.*\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"6.18.23\",\n                            \"lessThanOrEqual\": \"6.18.*\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"6.19.13\",\n                            \"lessThanOrEqual\": \"6.19.*\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"7.0\",\n                            \"lessThanOrEqual\": \"*\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"original_commit_for_fix\"\n                        }\n                    ]\n                }"}],"metrics":[{"system":"CVSS 3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","score":9.8,"severity":"CRITICAL"}],"references":["https://git.kernel.org/stable/c/513e06735f5be575b409d195822195348b164e48","https://git.kernel.org/stable/c/275bdf762e82082f064e60a92448fa2ac43cf95b","https://git.kernel.org/stable/c/a2b68a9a476b9544ff31f1fbcd5d80867a8a5e2f","https://git.kernel.org/stable/c/b7b8012193fd98236d7ae05d4b553f010a77b2ef","https://git.kernel.org/stable/c/2c91b39912278d0878f9ba60ba04d2518b18a08d","https://git.kernel.org/stable/c/6fca757c20396dc2e604dcc61922264e9e3dc803","https://git.kernel.org/stable/c/10d12b9240ebf96c785f0e2e4228318cd5f3a3eb","https://git.kernel.org/stable/c/51f4e090b9f87b40c21b6daadb5c06e6c0a07b67"],"sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2026-31649","license":"CVE Program Terms of Use","key":"cve-program:CVE-2026-31649","identifiers":["CVE-2026-31649"]},"retained":false,"historicalAffected":[]}],"coverage":[]}