net/sched: cls_route: fix fastmap use-after-free on filter
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.
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": [
{
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"version": "1109c00547fc66df45b9ff923544be4c1e1bec13",
"lessThan": "7897198b26445b4009a057bda1986b94a99e5d5f",
"versionType": "git"
},
{
"status": "affected",
"version": "1109c00547fc66df45b9ff923544be4c1e1bec13",
"lessThan": "820f083c294ad6d319c02a7d43294f2ed2565139",
"versionType": "git"
},
{
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"version": "1109c00547fc66df45b9ff923544be4c1e1bec13",
"lessThan": "5ec9001be6d0eb527251125632ec8fe88278897f",
"versionType": "git"
},
{
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"version": "1109c00547fc66df45b9ff923544be4c1e1bec13",
"lessThan": "b969984b2bdc85d721ce4047cd270cd37ec705a2",
"versionType": "git"
},
{
"status": "affected",
"version": "1109c00547fc66df45b9ff923544be4c1e1bec13",
"lessThan": "a17f636c9330eac879822ce29f998e5abd1b72c1",
"versionType": "git"
},
{
"status": "affected",
"version": "1109c00547fc66df45b9ff923544be4c1e1bec13",
"lessThan": "0e7a8cf8895b06d07c7311f028eba16ad742b9bc",
"versionType": "git"
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{
"status": "affected",
"version": "1109c00547fc66df45b9ff923544be4c1e1bec13",
"lessThan": "ae9aff87025219005a2d16b4fe83d6f24643e50d",
"versionType": "git"
},
{
"status": "affected",
"version": "1109c00547fc66df45b9ff923544be4c1e1bec13",
"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
- Added to Heist Feed
- Publisher date