{ "cvss": 7.8, "datePublished": "2026-05-01T14:16:19.907", "dateUpdated": "2026-09-08T09:17:59.693", "description": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet/packet: fix TOCTOU race on mmap'd vnet_hdr in tpacket_snd()\n\nIn tpacket_snd(), when PACKET_VNET_HDR is enabled, vnet_hdr points\ndirectly into the mmap'd TX ring buffer shared with userspace. The\nkernel validates the header via __packet_snd_vnet_parse() but then\nre-reads all fields later in virtio_net_hdr_to_skb(). A concurrent\nuserspace thread can modify the vnet_hdr fields between validation\nand use, bypassing all safety checks.\n\nThe non-TPACKET path (packet_snd()) already correctly copies vnet_hdr\nto a stack-local variable. All other vnet_hdr consumers in the kernel\n(tun.c, tap.c, virtio_net.c) also use stack copies. The TPACKET TX\npath is the only caller of virtio_net_hdr_to_skb() that reads directly\nfrom user-controlled shared memory.\n\nFix this by copying vnet_hdr from the mmap'd ring buffer to a\nstack-local variable before validation and use, consistent with the\napproach used in packet_snd() and all other callers.", "id": "CVE-2026-31700", "raw": { "affected": [ { "affectedData": [ { "defaultStatus": "unaffected", "product": "Linux", "programFiles": [ "net/packet/af_packet.c" ], "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "vendor": "Linux", "versions": [ { "lessThan": "0f4c9754956b86de158a4af5278c5cf5bda9439e", "status": "affected", "version": "1d036d25e5609ba73fee6a88db01c306b140d512", "versionType": "git" }, { "lessThan": "714aa973da8163925eda7efd49361ccbee21ee46", "status": "affected", "version": "1d036d25e5609ba73fee6a88db01c306b140d512", "versionType": "git" }, { "lessThan": "1490f82353bdabc09265a74e645b07f05cf4188e", "status": "affected", "version": "1d036d25e5609ba73fee6a88db01c306b140d512", "versionType": "git" }, { "lessThan": "74e2db36fe50e3ad9d5300d7fd0e6e2a15a6d121", "status": "affected", "version": "1d036d25e5609ba73fee6a88db01c306b140d512", "versionType": "git" }, { "lessThan": "3a1bf9116ea31470b89692585c3910dfe830dcdd", "status": "affected", "version": "1d036d25e5609ba73fee6a88db01c306b140d512", "versionType": "git" }, { "lessThan": "28324a3b62d9ce7f9bdd65a8ce63f382041d1b27", "status": "affected", "version": "1d036d25e5609ba73fee6a88db01c306b140d512", "versionType": "git" }, { "lessThan": "48a6ef291a17639e1b6ae0fbe9c8b2bb87d7804b", "status": "affected", "version": "1d036d25e5609ba73fee6a88db01c306b140d512", "versionType": "git" }, { "lessThan": "2c054e17d9d41f1020376806c7f750834ced4dc5", "status": "affected", "version": "1d036d25e5609ba73fee6a88db01c306b140d512", "versionType": "git" } ] }, { "defaultStatus": "affected", "product": "Linux", "programFiles": [ "net/packet/af_packet.c" ], "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "vendor": "Linux", "versions": [ { "status": "affected", "version": "4.6" }, { "lessThan": "4.6", "status": "unaffected", "version": "0", "versionType": "semver" }, { "lessThanOrEqual": "5.10.*", "status": "unaffected", "version": "5.10.259", "versionType": "semver" }, { "lessThanOrEqual": "5.15.*", "status": "unaffected", "version": "5.15.210", "versionType": "semver" }, { "lessThanOrEqual": "6.1.*", "status": "unaffected", "version": "6.1.176", "versionType": "semver" }, { "lessThanOrEqual": "6.6.*", "status": "unaffected", "version": "6.6.136", "versionType": "semver" }, { "lessThanOrEqual": "6.12.*", "status": "unaffected", "version": "6.12.84", "versionType": "semver" }, { "lessThanOrEqual": "6.18.*", "status": "unaffected", "version": "6.18.25", "versionType": "semver" }, { "lessThanOrEqual": "7.0.*", "status": "unaffected", "version": "7.0.2", "versionType": "semver" }, { "lessThanOrEqual": "*", "status": "unaffected", "version": "7.1", "versionType": "original_commit_for_fix" } ] } ], "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67" }, { "affectedData": [ { "defaultStatus": "unknown", "product": "SIMATIC S7-1500 CPU 1518-4 PN/DP MFP", "vendor": "Siemens", "versions": [ { "lessThan": "*", "status": "affected", "version": "V3.1.6", "versionType": "custom" } ] }, { "defaultStatus": "unknown", "product": "SIMATIC S7-1500 CPU 1518-4 PN/DP MFP", "vendor": "Siemens", "versions": [ { "lessThan": "*", "status": "affected", "version": "V3.1.6", "versionType": "custom" } ] }, { "defaultStatus": "unknown", "product": "SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP", "vendor": "Siemens", "versions": [ { "lessThan": "*", "status": "affected", "version": "V3.1.6", "versionType": "custom" } ] }, { "defaultStatus": "unknown", "product": "SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP", "vendor": "Siemens", "versions": [ { "lessThan": "*", "status": "affected", "version": "V3.1.6", "versionType": "custom" } ] }, { "defaultStatus": "unknown", "product": "SIPLUS S7-1500 CPU 1518-4 PN/DP MFP", "vendor": "Siemens", "versions": [ { "lessThan": "*", "status": "affected", "version": "V3.1.6", "versionType": "custom" } ] } ], "source": "0b142b55-0307-4c5a-b3c9-f314f3fb7c5e" } ], "configurations": [ { "nodes": [ { "cpeMatch": [ { "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "matchCriteriaId": "7A6CE177-C7BA-4E34-9D61-035565B5FFF5", "versionEndExcluding": "6.6.136", "versionStartIncluding": "4.6", "vulnerable": true }, { "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "matchCriteriaId": "D4ECA0DE-AFF5-4688-B219-4CA2336CA5B7", "versionEndExcluding": "6.12.84", "versionStartIncluding": "6.7", "vulnerable": true }, { "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "matchCriteriaId": "8B0A7E0E-F6D8-45DB-8CD9-01839FE40A6C", "versionEndExcluding": "6.18.25", "versionStartIncluding": "6.13", "vulnerable": true }, { "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "matchCriteriaId": "1BD58F1E-7C20-4C0D-92A2-FAC5CBFBE8A8", "versionEndExcluding": "7.0.2", "versionStartIncluding": "6.19", "vulnerable": true }, { "criteria": "cpe:2.3:o:linux:linux_kernel:7.1:rc1:*:*:*:*:*:*", "matchCriteriaId": "B1EF7059-E670-45F4-B422-54C40FA86390", "vulnerable": true }, { "criteria": "cpe:2.3:o:linux:linux_kernel:7.1:rc2:*:*:*:*:*:*", "matchCriteriaId": "0D38F0BF-A728-4133-A358-D44A2F7EE6D6", "vulnerable": true } ], "negate": false, "operator": "OR" } ] } ], "cveTags": [], "descriptions": [ { "lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet/packet: fix TOCTOU race on mmap'd vnet_hdr in tpacket_snd()\n\nIn tpacket_snd(), when PACKET_VNET_HDR is enabled, vnet_hdr points\ndirectly into the mmap'd TX ring buffer shared with userspace. The\nkernel validates the header via __packet_snd_vnet_parse() but then\nre-reads all fields later in virtio_net_hdr_to_skb(). A concurrent\nuserspace thread can modify the vnet_hdr fields between validation\nand use, bypassing all safety checks.\n\nThe non-TPACKET path (packet_snd()) already correctly copies vnet_hdr\nto a stack-local variable. All other vnet_hdr consumers in the kernel\n(tun.c, tap.c, virtio_net.c) also use stack copies. The TPACKET TX\npath is the only caller of virtio_net_hdr_to_skb() that reads directly\nfrom user-controlled shared memory.\n\nFix this by copying vnet_hdr from the mmap'd ring buffer to a\nstack-local variable before validation and use, consistent with the\napproach used in packet_snd() and all other callers." } ], "id": "CVE-2026-31700", "lastModified": "2026-09-08T09:17:59.693", "metrics": { "cvssMetricV31": [ { "cvssData": { "attackComplexity": "LOW", "attackVector": "LOCAL", "availabilityImpact": "HIGH", "baseScore": 7.8, "baseSeverity": "HIGH", "confidentialityImpact": "HIGH", "integrityImpact": "HIGH", "privilegesRequired": "LOW", "scope": "UNCHANGED", "userInteraction": "NONE", "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H", "version": "3.1" }, "exploitabilityScore": 1.8, "impactScore": 5.9, "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "type": "Secondary" } ] }, "published": "2026-05-01T14:16:19.907", "references": [ { "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "url": "https://git.kernel.org/stable/c/0f4c9754956b86de158a4af5278c5cf5bda9439e" }, { "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "url": "https://git.kernel.org/stable/c/1490f82353bdabc09265a74e645b07f05cf4188e" }, { "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": [ "Patch" ], "url": "https://git.kernel.org/stable/c/28324a3b62d9ce7f9bdd65a8ce63f382041d1b27" }, { "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": [ "Patch" ], "url": "https://git.kernel.org/stable/c/2c054e17d9d41f1020376806c7f750834ced4dc5" }, { "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": [ "Patch" ], "url": "https://git.kernel.org/stable/c/3a1bf9116ea31470b89692585c3910dfe830dcdd" }, { "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": [ "Patch" ], "url": "https://git.kernel.org/stable/c/48a6ef291a17639e1b6ae0fbe9c8b2bb87d7804b" }, { "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "url": "https://git.kernel.org/stable/c/714aa973da8163925eda7efd49361ccbee21ee46" }, { "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": [ "Patch" ], "url": "https://git.kernel.org/stable/c/74e2db36fe50e3ad9d5300d7fd0e6e2a15a6d121" }, { "source": "0b142b55-0307-4c5a-b3c9-f314f3fb7c5e", "url": "https://cert-portal.siemens.com/productcert/html/ssa-019113.html" } ], "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "vulnStatus": "Modified", "weaknesses": [ { "description": [ { "lang": "en", "value": "CWE-362" } ], "source": "nvd@nist.gov", "type": "Primary" } ] }, "severity": "HIGH", "source": "nvd", "title": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet/packet: fix TOCTOU race on mmap'd vnet_hdr i..." }