CVE-2026-74583

CVE CVE-2026-74583EUVD EUVD-2026-64005Published 2026-08-21T16:31:55.000ZLast changed 2026-08-25T05:40:10.000ZCVSS 7.8

What the advisory describes

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.

Source: EUVD (ENISA), in the words of the advisory.

Products the advisory names

These come from the advisory itself, not from any check we performed.

• Linux — Linux patch: 5.15.216; patch: 7.2; 1109c00547fc66df45b9ff923544be4c1e1bec13 <47d7f7051253bdc02b1d245d87e38f16d31a74df; 1109c00547fc66df45b9ff923544be4c1e1bec13 <ae9aff87025219005a2d16b4fe83d6f24643e50d; patch: 6.6.152; 1109c00547fc66df45b9ff923544be4c1e1bec13 <a17f636c9330eac879822ce29f998e5abd1b72c1; 1109c00547fc66df45b9ff923544be4c1e1bec13 <5ec9001be6d0eb527251125632ec8fe88278897f; patch: 6.12.104; patch: 6.1.183; 1109c00547fc66df45b9ff923544be4c1e1bec13 <b969984b2bdc85d721ce4047cd270cd37ec705a2; 1109c00547fc66df45b9ff923544be4c1e1bec13 <7897198b26445b4009a057bda1986b94a99e5d5f; patch: 5.10.265; 1109c00547fc66df45b9ff923544be4c1e1bec13 <820f083c294ad6d319c02a7d43294f2ed2565139; patch: 0; patch: 6.18.45; 3.18; 1109c00547fc66df45b9ff923544be4c1e1bec13 <0e7a8cf8895b06d07c7311f028eba16ad742b9bc; patch: 7.1.9

The versions shown are the advisory's own. Patchlage compares no version numbers and derives no judgement from them — which version is installed is something a person has to look up.

Carried in the product catalogue

An estate covering these products can be recorded in Patchlage. An advisory about them appears in the next morning's situation report.

• Linux — Linux

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