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

Type: advisorySource: Official CVE List1 source record

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.

Announced Source revision 1
Original source ↗

CVE-2026-74583

Primary source · Revision 1

Imported from structured advisory data. Source references identify upstream records or fields; verify affected versions and your deployed configuration.

Security context

Source reference: cve:CVE-2026-74583

Linux

Source reference: /containers/cna/affected/0/product

Affected versions
Not stated in this record
Fixed versions
Not stated in this record
Prerequisites
Not stated in this record

Linux

Source reference: /containers/cna/affected/1/product

Affected versions
Not stated in this record
Fixed versions
Not stated in this record
Prerequisites
Not stated in this record

Structured affected-version data

Original package identities and version rules from this source.

[
  {
    "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
    "vendor": "Linux",
    "product": "Linux",
    "versions": [
      {
        "status": "affected",
        "version": "1109c00547fc66df45b9ff923544be4c1e1bec13",
        "lessThan": "7897198b26445b4009a057bda1986b94a99e5d5f",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "1109c00547fc66df45b9ff923544be4c1e1bec13",
        "lessThan": "820f083c294ad6d319c02a7d43294f2ed2565139",
        "versionType": "git"
      },
      {
        "status": "affected",
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        "lessThan": "5ec9001be6d0eb527251125632ec8fe88278897f",
        "versionType": "git"
      },
      {
        "status": "affected",
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        "versionType": "git"
      },
      {
        "status": "affected",
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        "lessThan": "a17f636c9330eac879822ce29f998e5abd1b72c1",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "1109c00547fc66df45b9ff923544be4c1e1bec13",
        "lessThan": "0e7a8cf8895b06d07c7311f028eba16ad742b9bc",
        "versionType": "git"
      },
      {
        "status": "affected",
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        "lessThan": "ae9aff87025219005a2d16b4fe83d6f24643e50d",
        "versionType": "git"
      },
      {
        "status": "affected",
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        "lessThan": "47d7f7051253bdc02b1d245d87e38f16d31a74df",
        "versionType": "git"
      }
    ],
    "programFiles": [
      "net/sched/cls_route.c"
    ],
    "defaultStatus": "unaffected"
  },
  {
    "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
    "vendor": "Linux",
    "product": "Linux",
    "versions": [
      {
        "status": "affected",
        "version": "3.18"
      },
      {
        "status": "unaffected",
        "version": "0",
        "lessThan": "3.18",
        "versionType": "semver"
      },
      {
        "status": "unaffected",
        "version": "5.10.265",
        "versionType": "semver",
        "lessThanOrEqual": "5.10.*"
      },
      {
        "status": "unaffected",
        "version": "5.15.216",
        "versionType": "semver",
        "lessThanOrEqual": "5.15.*"
      },
      {
        "status": "unaffected",
        "version": "6.1.183",
        "versionType": "semver",
        "lessThanOrEqual": "6.1.*"
      },
      {
        "status": "unaffected",
        "version": "6.6.152",
        "versionType": "semver",
        "lessThanOrEqual": "6.6.*"
      },
      {
        "status": "unaffected",
        "version": "6.12.104",
        "versionType": "semver",
        "lessThanOrEqual": "6.12.*"
      },
      {
        "status": "unaffected",
        "version": "6.18.45",
        "versionType": "semver",
        "lessThanOrEqual": "6.18.*"
      },
      {
        "status": "unaffected",
        "version": "7.1.9",
        "versionType": "semver",
        "lessThanOrEqual": "7.1.*"
      },
      {
        "status": "unaffected",
        "version": "7.2",
        "versionType": "original_commit_for_fix",
        "lessThanOrEqual": "*"
      }
    ],
    "programFiles": [
      "net/sched/cls_route.c"
    ],
    "defaultStatus": "affected"
  }
]
Related CVEs
CVE-2026-74583

Source reference: /cveMetadata/cveId

Publisher severity

high

Source reference: /containers/cna/metrics

Event
#33221 · Revision 1
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Publisher date
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