{"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 ..."}