{ "dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": { "cveId": "CVE-2026-31649", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2026-03-09T15:48:24.128Z", "datePublished": "2026-04-24T14:45:02.520Z", "dateUpdated": "2026-08-05T12:24:08.585Z" }, "containers": { "cna": { "providerMetadata": { "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-08-05T12:24:08.585Z" }, "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." } ], "metrics": [ { "cvssV3_1": { "version": "3.1", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H", "baseScore": 9.8, "baseSeverity": "CRITICAL" }, "scenarios": [ { "lang": "en", "value": "AV:N - The vulnerable stmmac transmit path can be reached over the network when an unauthenticated peer causes a network-facing service or forwarding/router workload to transmit large non-linear skbs through an affected stmmac interface. This is a plausible deployment for embedded/router/NFS/TLS systems using this Ethernet MAC.\nAC:L - Once the system is using affected chain mode, the trigger is a non-linear packet whose total length exceeds the jumbo threshold while the linear head does not, which common scatter-gather/sendpage paths can produce. There is no race or attacker-uncontrolled timing requirement.\nPR:N - In the highest reasonable scenario, a remote unauthenticated client can trigger large page-backed responses or forwarded traffic through the vulnerable device. No local account or administrative capability is required for that network-triggered path.\nUI:N - No victim user action is needed beyond the system already running the affected driver and network service or forwarding configuration. The attacker can trigger transmission by network interaction.\nS:U - The vulnerability is in the host kernel network driver and impacts the same host kernel security authority. It does not cross a VM, IOMMU, or other separate security scope boundary by itself.\nC:H - The underflow makes the driver DMA-map addresses far beyond the skb buffer, exposing arbitrary kernel memory to the DMA engine and potentially onto the wire. That supports high confidentiality impact.\nI:H - The erroneous descriptor programming gives hardware DMA access to unintended kernel memory ranges and the fix description identifies potential memory corruption from hardware. Under the required tie-breaker, this is scored as high integrity impact.\nA:H - The huge wrapped loop and invalid DMA mappings can exhaust/overwrite TX descriptors, hit DMA/IOMMU faults, hang transmission, or crash the kernel. This is high availability impact." } ] } ], "affected": [ { "product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "drivers/net/ethernet/stmicro/stmmac/chain_mode.c" ], "versions": [ { "version": "286a837217204b1ef105e3a554d0757e4fdfaac1", "lessThan": "513e06735f5be575b409d195822195348b164e48", "status": "affected", "versionType": "git" }, { "version": "286a837217204b1ef105e3a554d0757e4fdfaac1", "lessThan": "275bdf762e82082f064e60a92448fa2ac43cf95b", "status": "affected", "versionType": "git" }, { "version": "286a837217204b1ef105e3a554d0757e4fdfaac1", "lessThan": "a2b68a9a476b9544ff31f1fbcd5d80867a8a5e2f", "status": "affected", "versionType": "git" }, { "version": "286a837217204b1ef105e3a554d0757e4fdfaac1", "lessThan": "b7b8012193fd98236d7ae05d4b553f010a77b2ef", "status": "affected", "versionType": "git" }, { "version": "286a837217204b1ef105e3a554d0757e4fdfaac1", "lessThan": "2c91b39912278d0878f9ba60ba04d2518b18a08d", "status": "affected", "versionType": "git" }, { "version": "286a837217204b1ef105e3a554d0757e4fdfaac1", "lessThan": "6fca757c20396dc2e604dcc61922264e9e3dc803", "status": "affected", "versionType": "git" }, { "version": "286a837217204b1ef105e3a554d0757e4fdfaac1", "lessThan": "10d12b9240ebf96c785f0e2e4228318cd5f3a3eb", "status": "affected", "versionType": "git" }, { "version": "286a837217204b1ef105e3a554d0757e4fdfaac1", "lessThan": "51f4e090b9f87b40c21b6daadb5c06e6c0a07b67", "status": "affected", "versionType": "git" } ] }, { "product": "Linux", "vendor": "Linux", "defaultStatus": "affected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "drivers/net/ethernet/stmicro/stmmac/chain_mode.c" ], "versions": [ { "version": "3.2", "status": "affected" }, { "version": "0", "lessThan": "3.2", "status": "unaffected", "versionType": "semver" }, { "version": "5.10.253", "lessThanOrEqual": "5.10.*", "status": "unaffected", "versionType": "semver" }, { "version": "5.15.203", "lessThanOrEqual": "5.15.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.1.169", "lessThanOrEqual": "6.1.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.6.135", "lessThanOrEqual": "6.6.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.12.82", "lessThanOrEqual": "6.12.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.18.23", "lessThanOrEqual": "6.18.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.19.13", "lessThanOrEqual": "6.19.*", "status": "unaffected", "versionType": "semver" }, { "version": "7.0", "lessThanOrEqual": "*", "status": "unaffected", "versionType": "original_commit_for_fix" } ] } ], "cpeApplicability": [ { "nodes": [ { "operator": "OR", "negate": false, "cpeMatch": [ { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "3.2", "versionEndExcluding": "5.10.253" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "3.2", "versionEndExcluding": "5.15.203" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "3.2", "versionEndExcluding": "6.1.169" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "3.2", "versionEndExcluding": "6.6.135" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "3.2", "versionEndExcluding": "6.12.82" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "3.2", "versionEndExcluding": "6.18.23" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "3.2", "versionEndExcluding": "6.19.13" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "3.2", "versionEndExcluding": "7.0" } ] } ] } ], "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" } }, "adp": [ { "x_adpType": "supplier", "providerMetadata": { 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