{"apiVersion":"1.0","identifier":"CVE-2026-74583","description":"In the Linux kernel, the following vulnerability has been resolved: net/sched: cls_route: fix fastmap use-after-free on filter The route4 classifier maintains a 16-slot fastmap cache that stores raw struct route4_filter pointers indexed by (id, iif). The reader (route4_classify) populates this cache via route4_set_fastmap() for every classified packet that hits a filter. The writer (route4_delete, route4_change) clears the cache via route4_reset_fastmap() before RCU-deferred kfree of the filter. This creates a UAF race: 1. Reader walks the RCU-protected bucket chain, finds filter f 2. Writer unlinks f, calls route4_reset_fastmap(), then tcf_queue_work() 3. Reader calls route4_set_fastmap() and writes f into the cache *after* the writer-s reset, caching a pointer about to be freed 4. After the RCU grace period, kfree(f) executes 5. Next classified packet on the same (id, iif) tuple hits the stale fastmap entry and reads f->res from freed memory Reproduced with an mdelay(100) accelerator in route4_set_fastmap() and a concurrent add/delete stress test (provided by both zdi and Santosh). Both triggered KASAN slab-use-after-free reports in the route4 fastmap paths. Fix: Introduce a per-filter boolean dying flag to suppress stale fastmap republishing by in-flight readers.","publishedAt":"2026-08-21T17:16:44","lastModifiedAt":"2026-08-25T06:18:32","sourceUrl":"https://nvd.nist.gov/vuln/detail/CVE-2026-74583","cvssScore":7.8,"cvssVector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","epssProbability":0.00117,"riskScore":0.79,"affectedProduct":"Linux kernel","affectedVersions":"unknown","vulnerabilityType":"Kernel","operatingSystems":[],"links":{"self":"https://www.redsauce.net/api/cves/CVE-2026-74583","webPages":{"es":"https://www.redsauce.net/es/cves/CVE-2026-74583","en":"https://www.redsauce.net/en/cves/CVE-2026-74583","fr":"https://www.redsauce.net/fr/cves/CVE-2026-74583","pt":"https://www.redsauce.net/pt/cves/CVE-2026-74583","de":"https://www.redsauce.net/de/cves/CVE-2026-74583","sk":"https://www.redsauce.net/sk/cves/CVE-2026-74583","el":"https://www.redsauce.net/el/cves/CVE-2026-74583"},"source":"https://nvd.nist.gov/vuln/detail/CVE-2026-74583"}}