{ "cvss": 5.5, "datePublished": "2026-04-13T14:16:11.740", "dateUpdated": "2026-11-05T22:18:29.940", "description": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet/sched: cls_fw: fix NULL pointer dereference on shared blocks\n\nThe old-method path in fw_classify() calls tcf_block_q() and\ndereferences q->handle. Shared blocks leave block->q NULL, causing a\nNULL deref when an empty cls_fw filter is attached to a shared block\nand a packet with a nonzero major skb mark is classified.\n\nReject the configuration in fw_change() when the old method (no\nTCA_OPTIONS) is used on a shared block, since fw_classify()'s\nold-method path needs block->q which is NULL for shared blocks.\n\nThe fixed null-ptr-deref calling stack:\n KASAN: null-ptr-deref in range [0x0000000000000038-0x000000000000003f]\n RIP: 0010:fw_classify (net/sched/cls_fw.c:81)\n Call Trace:\n tcf_classify (./include/net/tc_wrapper.h:197 net/sched/cls_api.c:1764 net/sched/cls_api.c:1860)\n tc_run (net/core/dev.c:4401)\n __dev_queue_xmit (net/core/dev.c:4535 net/core/dev.c:4790)", "id": "CVE-2026-31421", "raw": { "affected": [ { "affectedData": [ { "defaultStatus": "unaffected", "product": "Linux", "programFiles": [ "net/sched/cls_fw.c" ], "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "vendor": "Linux", "versions": [ { "lessThan": "d6d5bd62a09650856e1e2010eb09853eba0d64e1", "status": "affected", "version": "1abf272022cf1d18469405f47b4ec49c6a3125db", "versionType": "git" }, { "lessThan": "febf64ca79a2d6540ab6e5e197fa0f4f7e84473e", "status": "affected", "version": "1abf272022cf1d18469405f47b4ec49c6a3125db", "versionType": "git" }, { "lessThan": "3d41f9a314afa94b1c7c7c75405920123220e8cd", "status": "affected", "version": "1abf272022cf1d18469405f47b4ec49c6a3125db", "versionType": "git" }, { "lessThan": "18328eff2f97d1a6adcdb6d4a0f42f2f83a31e28", "status": "affected", "version": "1abf272022cf1d18469405f47b4ec49c6a3125db", "versionType": "git" }, { "lessThan": "5cf41031922c154aa5ccda8bcdb0f5e6226582ec", "status": "affected", "version": "1abf272022cf1d18469405f47b4ec49c6a3125db", "versionType": "git" }, { "lessThan": "3cb055df9e8625ce699a259d8178d67b37f2b160", "status": "affected", "version": "1abf272022cf1d18469405f47b4ec49c6a3125db", "versionType": "git" }, { "lessThan": "96426c348def662b06bfdc65be3002905604927a", "status": "affected", "version": "1abf272022cf1d18469405f47b4ec49c6a3125db", "versionType": "git" }, { "lessThan": "faeea8bbf6e958bf3c00cb08263109661975987c", "status": "affected", "version": "1abf272022cf1d18469405f47b4ec49c6a3125db", "versionType": "git" } ] }, { "defaultStatus": "affected", "product": "Linux", "programFiles": [ "net/sched/cls_fw.c" ], "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "vendor": "Linux", "versions": [ { "status": "affected", "version": "4.15" }, { "lessThan": "4.15", "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": "6.1.168", "versionType": "semver" }, { "lessThanOrEqual": "6.6.*", "status": "unaffected", "version": "6.6.134", "versionType": "semver" }, { "lessThanOrEqual": "6.12.*", "status": "unaffected", "version": "6.12.81", "versionType": "semver" }, { "lessThanOrEqual": "6.18.*", "status": "unaffected", "version": "6.18.22", "versionType": "semver" }, { "lessThanOrEqual": "6.19.*", "status": "unaffected", "version": "6.19.12", "versionType": "semver" }, { "lessThanOrEqual": "*", "status": "unaffected", "version": "7.0", "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": "V3.1.5", "versionType": "custom" } ] }, { "defaultStatus": "unknown", "product": "SIMATIC S7-1500 CPU 1518-4 PN/DP MFP", "vendor": "Siemens", "versions": [ { "lessThan": "*", "status": "affected", "version": "V3.1.7", "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 1518-4 PN/DP MFP", "vendor": "Siemens", "versions": [ { "lessThan": "*", "status": "affected", "version": "V3.1.5", "versionType": "custom" } ] }, { "defaultStatus": "unknown", "product": "SIMATIC S7-1500 CPU 1518-4 PN/DP MFP", "vendor": "Siemens", "versions": [ { "lessThan": "*", "status": "affected", "version": "V3.1.7", "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": "V3.1.5", "versionType": "custom" } ] }, { "defaultStatus": "unknown", "product": "SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP", "vendor": "Siemens", "versions": [ { "lessThan": "*", "status": "affected", "version": "V3.1.7", "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": "V3.1.5", "versionType": "custom" } ] }, { "defaultStatus": "unknown", "product": "SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP", "vendor": "Siemens", "versions": [ { "lessThan": "*", "status": "affected", "version": "V3.1.7", "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" } ] }, { "defaultStatus": "unknown", "product": "SIPLUS S7-1500 CPU 1518-4 PN/DP MFP", "vendor": "Siemens", "versions": [ { "lessThan": "*", "status": "affected", "version": "V3.1.5", "versionType": "custom" } ] }, { "defaultStatus": "unknown", "product": "SIPLUS S7-1500 CPU 1518-4 PN/DP MFP", "vendor": "Siemens", "versions": [ { "lessThan": "*", "status": "affected", "version": "V3.1.7", "versionType": "custom" } ] } ], "source": "0b142b55-0307-4c5a-b3c9-f314f3fb7c5e" } ], "configurations": [ { "nodes": [ { "cpeMatch": [ { "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "matchCriteriaId": "202FFB00-4CA7-44CB-ACA1-E88A2BF2264B", "versionEndExcluding": "5.10.253", "versionStartIncluding": "4.15", "vulnerable": true }, { "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "matchCriteriaId": "20DDB3E9-AABF-4107-ADB0-5362AA067045", "versionEndExcluding": "5.15.203", "versionStartIncluding": "5.11", "vulnerable": true }, { "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "matchCriteriaId": "E2DDDCA1-6DAB-4018-B920-8F045DDD8D3B", "versionEndExcluding": "6.1.168", "versionStartIncluding": "5.16", "vulnerable": true }, { "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "matchCriteriaId": "F56F925B-BAF8-4F4B-B62F-1496AF19A307", "versionEndExcluding": "6.6.134", "versionStartIncluding": "6.2", "vulnerable": true }, { "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "matchCriteriaId": "6EF80433-B33B-43C5-8E64-0FA7B8DCE1BC", "versionEndExcluding": "6.12.81", "versionStartIncluding": "6.7", "vulnerable": true }, { "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "matchCriteriaId": "C9DF8BCE-36D3-475D-9D21-19E4F02F9029", "versionEndExcluding": "6.18.22", "versionStartIncluding": "6.13", "vulnerable": true }, { "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "matchCriteriaId": "0A2B9540-02D5-41B4-B16A-82AF66FD4F36", "versionEndExcluding": "6.19.12", "versionStartIncluding": "6.19", "vulnerable": true }, { "criteria": "cpe:2.3:o:linux:linux_kernel:7.0:rc1:*:*:*:*:*:*", "matchCriteriaId": "F253B622-8837-4245-BCE5-A7BF8FC76A16", "vulnerable": true }, { "criteria": "cpe:2.3:o:linux:linux_kernel:7.0:rc2:*:*:*:*:*:*", "matchCriteriaId": "4AE85AD8-4641-4E7C-A2F4-305E2CD9EE64", "vulnerable": true }, { "criteria": "cpe:2.3:o:linux:linux_kernel:7.0:rc3:*:*:*:*:*:*", "matchCriteriaId": "F666C8D8-6538-46D4-B318-87610DE64C34", "vulnerable": true }, { "criteria": "cpe:2.3:o:linux:linux_kernel:7.0:rc4:*:*:*:*:*:*", "matchCriteriaId": "02259FDA-961B-47BC-AE7F-93D7EC6E90C2", "vulnerable": true }, { "criteria": "cpe:2.3:o:linux:linux_kernel:7.0:rc5:*:*:*:*:*:*", "matchCriteriaId": "58A9FEFF-C040-420D-8F0A-BFDAAA1DF258", "vulnerable": true }, { "criteria": "cpe:2.3:o:linux:linux_kernel:7.0:rc6:*:*:*:*:*:*", "matchCriteriaId": "1D2315C0-D46F-4F85-9754-F9E5E11374A6", "vulnerable": true } ], "negate": false, "operator": "OR" } ] } ], "cveTags": [], "descriptions": [ { "lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet/sched: cls_fw: fix NULL pointer dereference on shared blocks\n\nThe old-method path in fw_classify() calls tcf_block_q() and\ndereferences q->handle. Shared blocks leave block->q NULL, causing a\nNULL deref when an empty cls_fw filter is attached to a shared block\nand a packet with a nonzero major skb mark is classified.\n\nReject the configuration in fw_change() when the old method (no\nTCA_OPTIONS) is used on a shared block, since fw_classify()'s\nold-method path needs block->q which is NULL for shared blocks.\n\nThe fixed null-ptr-deref calling stack:\n KASAN: null-ptr-deref in range [0x0000000000000038-0x000000000000003f]\n RIP: 0010:fw_classify (net/sched/cls_fw.c:81)\n Call Trace:\n tcf_classify (./include/net/tc_wrapper.h:197 net/sched/cls_api.c:1764 net/sched/cls_api.c:1860)\n tc_run (net/core/dev.c:4401)\n __dev_queue_xmit (net/core/dev.c:4535 net/core/dev.c:4790)" } ], "id": "CVE-2026-31421", "lastModified": "2026-11-05T22:18:29.940", "metrics": { "cvssMetricV31": [ { "cvssData": { "attackComplexity": "LOW", "attackVector": "LOCAL", "availabilityImpact": "HIGH", "baseScore": 5.5, "baseSeverity": "MEDIUM", "confidentialityImpact": "NONE", "integrityImpact": "NONE", "privilegesRequired": "LOW", "scope": "UNCHANGED", "userInteraction": "NONE", "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H", "version": "3.1" }, "exploitabilityScore": 1.8, "impactScore": 3.6, "source": "nvd@nist.gov", "type": "Primary" } ], "ssvcV203": [ { "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "ssvcData": { "id": "CVE-2026-31421", "options": [ { "exploitation": "none" }, { "automatable": "no" }, { "technicalImpact": "partial" } ], "role": "CISA Coordinator", "timestamp": "2026-11-05T21:32:36.737622Z", "version": "2.0.3" } } ] }, "published": "2026-04-13T14:16:11.740", "references": [ { "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": [ "Patch" ], "url": "https://git.kernel.org/stable/c/18328eff2f97d1a6adcdb6d4a0f42f2f83a31e28" }, { "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": [ "Patch" ], "url": "https://git.kernel.org/stable/c/3cb055df9e8625ce699a259d8178d67b37f2b160" }, { "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": [ "Patch" ], "url": "https://git.kernel.org/stable/c/3d41f9a314afa94b1c7c7c75405920123220e8cd" }, { "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": [ "Patch" ], "url": "https://git.kernel.org/stable/c/5cf41031922c154aa5ccda8bcdb0f5e6226582ec" }, { "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": [ "Patch" ], "url": "https://git.kernel.org/stable/c/96426c348def662b06bfdc65be3002905604927a" }, { "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": [ "Patch" ], "url": "https://git.kernel.org/stable/c/d6d5bd62a09650856e1e2010eb09853eba0d64e1" }, { "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": [ "Patch" ], "url": "https://git.kernel.org/stable/c/faeea8bbf6e958bf3c00cb08263109661975987c" }, { "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": [ "Patch" ], "url": "https://git.kernel.org/stable/c/febf64ca79a2d6540ab6e5e197fa0f4f7e84473e" }, { "source": "0b142b55-0307-4c5a-b3c9-f314f3fb7c5e", "url": "https://cert-portal.siemens.com/productcert/html/ssa-019113.html" }, { "source": "0b142b55-0307-4c5a-b3c9-f314f3fb7c5e", "url": "https://cert-portal.siemens.com/productcert/html/ssa-082556.html" }, { "source": "0b142b55-0307-4c5a-b3c9-f314f3fb7c5e", "url": "https://cert-portal.siemens.com/productcert/html/ssa-457936.html" } ], "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "vulnStatus": "Modified", "weaknesses": [ { "description": [ { "lang": "en", "value": "CWE-476" } ], "source": "nvd@nist.gov", "type": "Primary" } ] }, "severity": "MEDIUM", "source": "nvd", "title": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet/sched: cls_fw: fix NULL pointer dereference ..." }