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CVE-2026-74583

net/sched: cls_route: fix fastmap use-after-free on filter

Published
Last modified
published
Not listed in CISA KEV
Fix
Fixed in 5.10.265, 5.15.216, 6.1.183, 6.6.152, 6.12.104, and 2 more
None on Exploit-DB, Metasploit or GitHub
  • Exploitation: none
  • Automatable: no
  • Technical impact: total

Summary

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.

Timeline

  1. CVE published
  2. CISA SSVC assessment

    Exploitation: none · Automatable: no · Technical impact: total

  3. Record last updated

Affected versions

  • Linux Linux

    From 1109c00547fc66df45b9ff923544be4c1e1bec13 · fixed in 7897198b26445b4009a057bda1986b94a99e5d5f; From 1109c00547fc66df45b9ff923544be4c1e1bec13 · fixed in 820f083c294ad6d319c02a7d43294f2ed2565139; From 1109c00547fc66df45b9ff923544be4c1e1bec13 · fixed in 5ec9001be6d0eb527251125632ec8fe88278897f; From 1109c00547fc66df45b9ff923544be4c1e1bec13 · fixed in b969984b2bdc85d721ce4047cd270cd37ec705a2; From 1109c00547fc66df45b9ff923544be4c1e1bec13 · fixed in a17f636c9330eac879822ce29f998e5abd1b72c1; From 1109c00547fc66df45b9ff923544be4c1e1bec13 · fixed in 0e7a8cf8895b06d07c7311f028eba16ad742b9bc; From 1109c00547fc66df45b9ff923544be4c1e1bec13 · fixed in ae9aff87025219005a2d16b4fe83d6f24643e50d; From 1109c00547fc66df45b9ff923544be4c1e1bec13 · fixed in 47d7f7051253bdc02b1d245d87e38f16d31a74df

  • Linux Linux

    3.18

  • KernelLinux

    From 3.18.0 · fixed in 5.10.265; From 5.11.0 · fixed in 5.15.216; From 5.16.0 · fixed in 6.1.183; From 6.2.0 · fixed in 6.6.152; From 6.7.0 · fixed in 6.12.104; From 6.13.0 · fixed in 6.18.45; From 6.19.0 · fixed in 7.1.9

References 8

git.kernel.org