{"cve":"CVE-2026-74583","nvd":{"published":"2026-08-21T17:16:44.643","modified":"2026-10-16T20:17:40.370","status":"Received","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nnet/sched: cls_route: fix fastmap use-after-free on filter\n\nThe route4 classifier maintains a 16-slot fastmap cache that stores raw\nstruct route4_filter pointers indexed by (id, iif). The reader\n(route4_classify) populates this cache via route4_set_fastmap() for every\nclassified packet that hits a filter. The writer (route4_delete,\nroute4_change) clears the cache via route4_reset_fastmap() before\nRCU-deferred kfree of the filter.\n\nThis creates a UAF race:\n 1. Reader walks the RCU-protected bucket chain, finds filter f\n 2. Writer unlinks f, calls route4_reset_fastmap(), then tcf_queue_work()\n 3. Reader calls route4_set_fastmap() and writes f into the cache\n    *after* the writer's reset, caching a pointer about to be freed\n 4. After the RCU grace period, kfree(f) executes\n 5. Next classified packet on the same (id, iif) tuple hits the stale\n    fastmap entry and reads f->res from freed memory\n\nReproduced with an mdelay(100) accelerator in route4_set_fastmap() and a\nconcurrent add/delete stress test (provided by both zdi and Santosh).\nBoth triggered KASAN slab-use-after-free reports in the route4 fastmap\npaths.\n\nFix:\nIntroduce a per-filter boolean dying flag to suppress stale fastmap\nrepublishing by in-flight readers.","cvss_v4":null,"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","score":7.8},"cwes":[],"references":["https://git.kernel.org/stable/c/0e7a8cf8895b06d07c7311f028eba16ad742b9bc","https://git.kernel.org/stable/c/47d7f7051253bdc02b1d245d87e38f16d31a74df","https://git.kernel.org/stable/c/5ec9001be6d0eb527251125632ec8fe88278897f","https://git.kernel.org/stable/c/7897198b26445b4009a057bda1986b94a99e5d5f","https://git.kernel.org/stable/c/820f083c294ad6d319c02a7d43294f2ed2565139"],"products":[],"source":"nvd","synced_at":"2026-10-19T22:49:38.260478770+00:00"},"epss":{"cve":"CVE-2026-74583","score":0.00117,"percentile":0.01651,"date":"2026-10-25"},"kev":null,"osv":[],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}