{"api_version":"1","generated_at":"2026-04-25T23:29:13+00:00","cve":"CVE-2026-31649","urls":{"html":"https://cve.report/CVE-2026-31649","api":"https://cve.report/api/cve/CVE-2026-31649.json","docs":"https://cve.report/api","cve_org":"https://www.cve.org/CVERecord?id=CVE-2026-31649","nvd":"https://nvd.nist.gov/vuln/detail/CVE-2026-31649"},"summary":{"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":"PUBLISHED","assigner":"Linux","published_at":"2026-04-24 15:16:44","updated_at":"2026-04-24 17:51:40"},"problem_types":[],"metrics":[],"references":[{"url":"https://git.kernel.org/stable/c/6fca757c20396dc2e604dcc61922264e9e3dc803","name":"https://git.kernel.org/stable/c/6fca757c20396dc2e604dcc61922264e9e3dc803","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/a2b68a9a476b9544ff31f1fbcd5d80867a8a5e2f","name":"https://git.kernel.org/stable/c/a2b68a9a476b9544ff31f1fbcd5d80867a8a5e2f","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/10d12b9240ebf96c785f0e2e4228318cd5f3a3eb","name":"https://git.kernel.org/stable/c/10d12b9240ebf96c785f0e2e4228318cd5f3a3eb","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/2c91b39912278d0878f9ba60ba04d2518b18a08d","name":"https://git.kernel.org/stable/c/2c91b39912278d0878f9ba60ba04d2518b18a08d","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/275bdf762e82082f064e60a92448fa2ac43cf95b","name":"https://git.kernel.org/stable/c/275bdf762e82082f064e60a92448fa2ac43cf95b","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/51f4e090b9f87b40c21b6daadb5c06e6c0a07b67","name":"https://git.kernel.org/stable/c/51f4e090b9f87b40c21b6daadb5c06e6c0a07b67","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/513e06735f5be575b409d195822195348b164e48","name":"https://git.kernel.org/stable/c/513e06735f5be575b409d195822195348b164e48","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/b7b8012193fd98236d7ae05d4b553f010a77b2ef","name":"https://git.kernel.org/stable/c/b7b8012193fd98236d7ae05d4b553f010a77b2ef","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-31649","name":"CVE Program record","refsource":"CVE.ORG","tags":["canonical"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-31649","name":"NVD vulnerability detail","refsource":"NVD","tags":["canonical","analysis"]}],"affected":[{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 286a837217204b1ef105e3a554d0757e4fdfaac1 513e06735f5be575b409d195822195348b164e48 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 286a837217204b1ef105e3a554d0757e4fdfaac1 275bdf762e82082f064e60a92448fa2ac43cf95b git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 286a837217204b1ef105e3a554d0757e4fdfaac1 a2b68a9a476b9544ff31f1fbcd5d80867a8a5e2f git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 286a837217204b1ef105e3a554d0757e4fdfaac1 b7b8012193fd98236d7ae05d4b553f010a77b2ef git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 286a837217204b1ef105e3a554d0757e4fdfaac1 2c91b39912278d0878f9ba60ba04d2518b18a08d git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 286a837217204b1ef105e3a554d0757e4fdfaac1 6fca757c20396dc2e604dcc61922264e9e3dc803 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 286a837217204b1ef105e3a554d0757e4fdfaac1 10d12b9240ebf96c785f0e2e4228318cd5f3a3eb git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 286a837217204b1ef105e3a554d0757e4fdfaac1 51f4e090b9f87b40c21b6daadb5c06e6c0a07b67 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 3.2","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 3.2 semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 5.10.253 5.10.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 5.15.203 5.15.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 6.1.169 6.1.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 6.6.135 6.6.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 6.12.82 6.12.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 6.18.23 6.18.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 6.19.13 6.19.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 7.0 * original_commit_for_fix","platforms":[]}],"timeline":[],"solutions":[],"workarounds":[],"exploits":[],"credits":[],"nvd_cpes":[],"vendor_comments":[],"enrichments":{"kev":null,"epss":null,"legacy_qids":[]},"source_records":{"cve_program":{"containers":{"cna":{"affected":[{"defaultStatus":"unaffected","product":"Linux","programFiles":["drivers/net/ethernet/stmicro/stmmac/chain_mode.c"],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","vendor":"Linux","versions":[{"lessThan":"513e06735f5be575b409d195822195348b164e48","status":"affected","version":"286a837217204b1ef105e3a554d0757e4fdfaac1","versionType":"git"},{"lessThan":"275bdf762e82082f064e60a92448fa2ac43cf95b","status":"affected","version":"286a837217204b1ef105e3a554d0757e4fdfaac1","versionType":"git"},{"lessThan":"a2b68a9a476b9544ff31f1fbcd5d80867a8a5e2f","status":"affected","version":"286a837217204b1ef105e3a554d0757e4fdfaac1","versionType":"git"},{"lessThan":"b7b8012193fd98236d7ae05d4b553f010a77b2ef","status":"affected","version":"286a837217204b1ef105e3a554d0757e4fdfaac1","versionType":"git"},{"lessThan":"2c91b39912278d0878f9ba60ba04d2518b18a08d","status":"affected","version":"286a837217204b1ef105e3a554d0757e4fdfaac1","versionType":"git"},{"lessThan":"6fca757c20396dc2e604dcc61922264e9e3dc803","status":"affected","version":"286a837217204b1ef105e3a554d0757e4fdfaac1","versionType":"git"},{"lessThan":"10d12b9240ebf96c785f0e2e4228318cd5f3a3eb","status":"affected","version":"286a837217204b1ef105e3a554d0757e4fdfaac1","versionType":"git"},{"lessThan":"51f4e090b9f87b40c21b6daadb5c06e6c0a07b67","status":"affected","version":"286a837217204b1ef105e3a554d0757e4fdfaac1","versionType":"git"}]},{"defaultStatus":"affected","product":"Linux","programFiles":["drivers/net/ethernet/stmicro/stmmac/chain_mode.c"],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","vendor":"Linux","versions":[{"status":"affected","version":"3.2"},{"lessThan":"3.2","status":"unaffected","version":"0","versionType":"semver"},{"lessThanOrEqual":"5.10.*","status":"unaffected","version":"5.10.253","versionType":"semver"},{"lessThanOrEqual":"5.15.*","status":"unaffected","version":"5.15.203","versionType":"semver"},{"lessThanOrEqual":"6.1.*","status":"unaffected","version":"6.1.169","versionType":"semver"},{"lessThanOrEqual":"6.6.*","status":"unaffected","version":"6.6.135","versionType":"semver"},{"lessThanOrEqual":"6.12.*","status":"unaffected","version":"6.12.82","versionType":"semver"},{"lessThanOrEqual":"6.18.*","status":"unaffected","version":"6.18.23","versionType":"semver"},{"lessThanOrEqual":"6.19.*","status":"unaffected","version":"6.19.13","versionType":"semver"},{"lessThanOrEqual":"*","status":"unaffected","version":"7.0","versionType":"original_commit_for_fix"}]}],"cpeApplicability":[{"nodes":[{"cpeMatch":[{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"5.10.253","versionStartIncluding":"3.2","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"5.15.203","versionStartIncluding":"3.2","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"6.1.169","versionStartIncluding":"3.2","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"6.6.135","versionStartIncluding":"3.2","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"6.12.82","versionStartIncluding":"3.2","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"6.18.23","versionStartIncluding":"3.2","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"6.19.13","versionStartIncluding":"3.2","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"7.0","versionStartIncluding":"3.2","vulnerable":true}],"negate":false,"operator":"OR"}]}],"descriptions":[{"lang":"en","value":"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."}],"providerMetadata":{"dateUpdated":"2026-04-24T14:45:02.520Z","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","shortName":"Linux"},"references":[{"url":"https://git.kernel.org/stable/c/513e06735f5be575b409d195822195348b164e48"},{"url":"https://git.kernel.org/stable/c/275bdf762e82082f064e60a92448fa2ac43cf95b"},{"url":"https://git.kernel.org/stable/c/a2b68a9a476b9544ff31f1fbcd5d80867a8a5e2f"},{"url":"https://git.kernel.org/stable/c/b7b8012193fd98236d7ae05d4b553f010a77b2ef"},{"url":"https://git.kernel.org/stable/c/2c91b39912278d0878f9ba60ba04d2518b18a08d"},{"url":"https://git.kernel.org/stable/c/6fca757c20396dc2e604dcc61922264e9e3dc803"},{"url":"https://git.kernel.org/stable/c/10d12b9240ebf96c785f0e2e4228318cd5f3a3eb"},{"url":"https://git.kernel.org/stable/c/51f4e090b9f87b40c21b6daadb5c06e6c0a07b67"}],"title":"net: stmmac: fix integer underflow in chain mode","x_generator":{"engine":"bippy-1.2.0"}}},"cveMetadata":{"assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","assignerShortName":"Linux","cveId":"CVE-2026-31649","datePublished":"2026-04-24T14:45:02.520Z","dateReserved":"2026-03-09T15:48:24.128Z","dateUpdated":"2026-04-24T14:45:02.520Z","state":"PUBLISHED"},"dataType":"CVE_RECORD","dataVersion":"5.2"},"nvd":{"publishedDate":"2026-04-24 15:16:44","lastModifiedDate":"2026-04-24 17:51:40","problem_types":[],"metrics":[],"configurations":[]},"legacy_mitre":{"record":{"CveYear":"2026","CveId":"31649","Ordinal":"1","Title":"net: stmmac: fix integer underflow in chain mode","CVE":"CVE-2026-31649","Year":"2026"},"notes":[{"CveYear":"2026","CveId":"31649","Ordinal":"1","NoteData":"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.","Type":"Description","Title":"net: stmmac: fix integer underflow in chain mode"}]}}}