{"id":"CVE-2026-31422","title":"net/sched: cls_flow: fix NULL pointer dereference on shared blocks","summary":"In the Linux kernel, the following vulnerability has been resolved:\n\nnet/sched: cls_flow: fix NULL pointer dereference on shared blocks\n\nflow_change() calls tcf_block_q() and dereferences q->handle to derive\na default baseclass.  Shared …","severity":"none","vendor":"Linux","product":"Linux","affected":["Linux >= 1abf272022cf1d18469405f47b4ec49c6a3125db < 57f94ac7e953eece5ed4819605a18f3cdfc63dcc","Linux >= 1abf272022cf1d18469405f47b4ec49c6a3125db < 942813276edeb1741fa5b0a73471beb4e495fa08","Linux >= 1abf272022cf1d18469405f47b4ec49c6a3125db < cc707a4fd4c3b6ab2722e06bc359aa010e13d408","Linux >= 1abf272022cf1d18469405f47b4ec49c6a3125db < 4a09f72007201c9f667dc47f64517ec23eea65e5","Linux >= 1abf272022cf1d18469405f47b4ec49c6a3125db < 9bf5fc36a43f7b8b5507c96e74fb81f1e8b4957e","Linux >= 1abf272022cf1d18469405f47b4ec49c6a3125db < a208c3e1232997e9317887294c20008dfcb75449","Linux >= 1abf272022cf1d18469405f47b4ec49c6a3125db < 415ea0c973c754b9f375225807810eb9045f4293","Linux >= 1abf272022cf1d18469405f47b4ec49c6a3125db < 1a280dd4bd1d616a01d6ffe0de284c907b555504","Linux 4.15"],"published":"2026-04-13","updated":"2026-09-08","sourceUpdated":"2026-09-08T08:46:58.481Z","source":"CVEORG","sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2026-31422","references":[{"url":"https://git.kernel.org/stable/c/57f94ac7e953eece5ed4819605a18f3cdfc63dcc"},{"url":"https://git.kernel.org/stable/c/942813276edeb1741fa5b0a73471beb4e495fa08"},{"url":"https://git.kernel.org/stable/c/cc707a4fd4c3b6ab2722e06bc359aa010e13d408"},{"url":"https://git.kernel.org/stable/c/4a09f72007201c9f667dc47f64517ec23eea65e5"},{"url":"https://git.kernel.org/stable/c/9bf5fc36a43f7b8b5507c96e74fb81f1e8b4957e"},{"url":"https://git.kernel.org/stable/c/a208c3e1232997e9317887294c20008dfcb75449"},{"url":"https://git.kernel.org/stable/c/415ea0c973c754b9f375225807810eb9045f4293"},{"url":"https://git.kernel.org/stable/c/1a280dd4bd1d616a01d6ffe0de284c907b555504"}],"tags":["cve.org"],"epss":0.00122,"epssPercentile":0.02321,"ingestedAt":"2026-09-08T15:33:26.991Z","slug":"CVE-2026-31422","body":"## Overview\n\nIn the Linux kernel, the following vulnerability has been resolved:\n\nnet/sched: cls_flow: fix NULL pointer dereference on shared blocks\n\nflow_change() calls tcf_block_q() and dereferences q->handle to derive\na default baseclass.  Shared blocks leave block->q NULL, causing a NULL\nderef when a flow filter without a fully qualified baseclass is created\non a shared block.\n\nCheck tcf_block_shared() before accessing block->q and return -EINVAL\nfor shared blocks.  This avoids the null-deref shown below:\n\n=======================================================================\nKASAN: null-ptr-deref in range [0x0000000000000038-0x000000000000003f]\nRIP: 0010:flow_change (net/sched/cls_flow.c:508)\nCall Trace:\n tc_new_tfilter (net/sched/cls_api.c:2432)\n rtnetlink_rcv_msg (net/core/rtnetlink.c:6980)\n [...]\n=======================================================================\n\n## Affected\n\n- `Linux >= 1abf272022cf1d18469405f47b4ec49c6a3125db < 57f94ac7e953eece5ed4819605a18f3cdfc63dcc`\n- `Linux >= 1abf272022cf1d18469405f47b4ec49c6a3125db < 942813276edeb1741fa5b0a73471beb4e495fa08`\n- `Linux >= 1abf272022cf1d18469405f47b4ec49c6a3125db < cc707a4fd4c3b6ab2722e06bc359aa010e13d408`\n- `Linux >= 1abf272022cf1d18469405f47b4ec49c6a3125db < 4a09f72007201c9f667dc47f64517ec23eea65e5`\n- `Linux >= 1abf272022cf1d18469405f47b4ec49c6a3125db < 9bf5fc36a43f7b8b5507c96e74fb81f1e8b4957e`\n- `Linux >= 1abf272022cf1d18469405f47b4ec49c6a3125db < a208c3e1232997e9317887294c20008dfcb75449`\n- `Linux >= 1abf272022cf1d18469405f47b4ec49c6a3125db < 415ea0c973c754b9f375225807810eb9045f4293`\n- `Linux >= 1abf272022cf1d18469405f47b4ec49c6a3125db < 1a280dd4bd1d616a01d6ffe0de284c907b555504`\n- `Linux 4.15`\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.","depth":"sunlit","depthScore":3,"depthScoreParts":{"impact":2.8,"likelihood":0,"exploitation":0,"ransomware":0},"changes":[]}