CVE-2026-53264 (GCVE-0-2026-53264)
Vulnerability from cvelistv5
Published
2026-06-25 08:39
Modified
2026-08-05 12:34
Severity ?
VLAI Severity ?
EPSS score ?
Summary
In the Linux kernel, the following vulnerability has been resolved:
net/sched: act_api: use RCU with deferred freeing for action lifecycle
When NEWTFILTER and DELFILTER are run concurrently it is possible to create a
race with an associated action.
Let's illustrate with CPU0 running NEWTFILTER and CPU1 running DELFILTER:
0: mutex_lock() <-- holds the idr lock
0: rcu_read_lock()
0: p = idr_find(idr, index) <-- action p is valid (RCU protects IDR)
0: mutex_unlock() <-- releases the idr lock
1: refcount_dec_and_mutex_lock() <-- refcnt 1->0, mutex held
1: idr_remove(idr, index) <-- Action removed from IDR
1: mutex_unlock() <-- mutex released allowing us to delete the action
1: tcf_action_cleanup(p); kfree(p) <-- Kfrees p immediately, no deferral
0: refcount_inc_not_zero(&p->tcfa_refcnt) <-- ouch, UAF p points to freed memory
This patch fixes the race condition between NEWTFILTER and DELFILTER by
adding struct rcu_head to tc_action used in the deferral and introducing a
call_rcu() in the delete path to defer the final kfree().
Note: this is a revert of commit d7fb60b9cafb ("net_sched: get rid of tcfa_rcu")
but also modernization/simplification to directly use kfree_rcu().
Let's illustrate the new restored code path:
0: rcu_read_lock()
1: refcount_dec_and_mutex_lock() <-- refcnt 1->0, mutex held
1: idr_remove(idr, index)
1: mutex_unlock()
1: call_rcu(&p->tcfa_rcu, tcf_action_rcu_free) <-- defer kfree after grace period
0: p = idr_find(idr, index)
0: refcount_inc_not_zero(&p->tcfa_refcnt) <-- fails, refcnt already 0
1: rcu_read_unlock() <-- release so freeing can run after grace period
After CPU1 calls idr_remove(), the object is no longer reachable through the IDR.
CPU0's subsequent idr_find() will return NULL, and even if it still held a
stale pointer, the immediate kfree() is now deferred until after the RCU grace
period, so no UAF can occur.
References
Impacted products
| Vendor | Product | Version | ||
|---|---|---|---|---|
| Linux | Linux |
Version: d7fb60b9cafb982cb2e46a267646a8dfd4f2e5da Version: d7fb60b9cafb982cb2e46a267646a8dfd4f2e5da Version: d7fb60b9cafb982cb2e46a267646a8dfd4f2e5da Version: d7fb60b9cafb982cb2e46a267646a8dfd4f2e5da Version: d7fb60b9cafb982cb2e46a267646a8dfd4f2e5da Version: d7fb60b9cafb982cb2e46a267646a8dfd4f2e5da Version: d7fb60b9cafb982cb2e46a267646a8dfd4f2e5da Version: d7fb60b9cafb982cb2e46a267646a8dfd4f2e5da |
||
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A kernel heap UAF can be shaped into disclosure primitives, so confidentiality impact is High.\\nI:H - The stale freed action pointer can be reused after heap reallocation and then modified/dereferenced through refcount, bind count, ops, and action lifecycle fields. This is memory corruption that can plausibly support arbitrary write or code execution, so integrity impact is High.\\nA:H - Even without full exploitation, the UAF can dereference or mutate freed/reused kernel memory and can crash or oops the kernel. Availability impact is therefore High.\"}]}], \"affected\": [{\"repo\": \"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\", \"vendor\": \"Linux\", \"product\": \"Linux\", \"versions\": [{\"status\": \"affected\", \"version\": \"d7fb60b9cafb982cb2e46a267646a8dfd4f2e5da\", \"lessThan\": \"98b2e40879abf0245be5a5b7af69e0f6ff524ac3\", \"versionType\": \"git\"}, {\"status\": \"affected\", \"version\": \"d7fb60b9cafb982cb2e46a267646a8dfd4f2e5da\", \"lessThan\": \"18af5d2ef0c4f65787fd1280c8b23286b9f2a835\", \"versionType\": \"git\"}, {\"status\": \"affected\", \"version\": \"d7fb60b9cafb982cb2e46a267646a8dfd4f2e5da\", \"lessThan\": \"1f1b98fea6b9ea30507d0f2fbff6750292d097e2\", \"versionType\": \"git\"}, {\"status\": \"affected\", \"version\": \"d7fb60b9cafb982cb2e46a267646a8dfd4f2e5da\", \"lessThan\": \"8b136f18ac4b2ace5aaad3305b3f8a5d8165a009\", \"versionType\": \"git\"}, {\"status\": \"affected\", \"version\": \"d7fb60b9cafb982cb2e46a267646a8dfd4f2e5da\", \"lessThan\": \"5dd51e09020c65aa53cf128e5e3517cd53b3c113\", \"versionType\": \"git\"}, {\"status\": \"affected\", \"version\": \"d7fb60b9cafb982cb2e46a267646a8dfd4f2e5da\", \"lessThan\": \"b60e9391142e983fab2be53497aa8f71fdd09cd5\", \"versionType\": \"git\"}, {\"status\": \"affected\", \"version\": \"d7fb60b9cafb982cb2e46a267646a8dfd4f2e5da\", \"lessThan\": \"91d105d2cbe002f9c7b43a6183adedc37e1da1f7\", \"versionType\": \"git\"}, {\"status\": \"affected\", \"version\": \"d7fb60b9cafb982cb2e46a267646a8dfd4f2e5da\", \"lessThan\": \"5057e1aca011e51ef51498c940ef96f3d3e8a305\", \"versionType\": \"git\"}], \"programFiles\": [\"include/net/act_api.h\", \"net/sched/act_api.c\"], \"defaultStatus\": \"unaffected\"}, {\"repo\": \"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\", \"vendor\": \"Linux\", \"product\": \"Linux\", \"versions\": [{\"status\": \"affected\", \"version\": \"4.14\"}, {\"status\": \"unaffected\", \"version\": \"0\", \"lessThan\": \"4.14\", \"versionType\": \"semver\"}, {\"status\": \"unaffected\", \"version\": \"5.10.259\", \"versionType\": \"semver\", \"lessThanOrEqual\": \"5.10.*\"}, {\"status\": \"unaffected\", \"version\": \"5.15.210\", \"versionType\": \"semver\", \"lessThanOrEqual\": \"5.15.*\"}, {\"status\": \"unaffected\", \"version\": \"6.1.176\", \"versionType\": \"semver\", \"lessThanOrEqual\": \"6.1.*\"}, {\"status\": \"unaffected\", \"version\": \"6.6.143\", \"versionType\": \"semver\", \"lessThanOrEqual\": \"6.6.*\"}, {\"status\": \"unaffected\", \"version\": \"6.12.94\", \"versionType\": \"semver\", \"lessThanOrEqual\": \"6.12.*\"}, {\"status\": \"unaffected\", \"version\": \"6.18.36\", \"versionType\": \"semver\", \"lessThanOrEqual\": \"6.18.*\"}, {\"status\": \"unaffected\", \"version\": \"7.0.13\", \"versionType\": \"semver\", \"lessThanOrEqual\": \"7.0.*\"}, {\"status\": \"unaffected\", \"version\": \"7.1\", \"versionType\": \"original_commit_for_fix\", \"lessThanOrEqual\": \"*\"}], \"programFiles\": [\"include/net/act_api.h\", \"net/sched/act_api.c\"], \"defaultStatus\": \"affected\"}], \"references\": [{\"url\": \"https://git.kernel.org/stable/c/98b2e40879abf0245be5a5b7af69e0f6ff524ac3\"}, {\"url\": \"https://git.kernel.org/stable/c/18af5d2ef0c4f65787fd1280c8b23286b9f2a835\"}, {\"url\": \"https://git.kernel.org/stable/c/1f1b98fea6b9ea30507d0f2fbff6750292d097e2\"}, {\"url\": \"https://git.kernel.org/stable/c/8b136f18ac4b2ace5aaad3305b3f8a5d8165a009\"}, {\"url\": \"https://git.kernel.org/stable/c/5dd51e09020c65aa53cf128e5e3517cd53b3c113\"}, {\"url\": \"https://git.kernel.org/stable/c/b60e9391142e983fab2be53497aa8f71fdd09cd5\"}, {\"url\": \"https://git.kernel.org/stable/c/91d105d2cbe002f9c7b43a6183adedc37e1da1f7\"}, {\"url\": \"https://git.kernel.org/stable/c/5057e1aca011e51ef51498c940ef96f3d3e8a305\"}], \"x_generator\": {\"engine\": \"bippy-1.2.0\"}, \"descriptions\": [{\"lang\": \"en\", \"value\": \"In the Linux kernel, the following vulnerability has been resolved:\\n\\nnet/sched: act_api: use RCU with deferred freeing for action lifecycle\\n\\nWhen NEWTFILTER and DELFILTER are run concurrently it is possible to create a\\nrace with an associated action.\\n\\nLet\u0027s illustrate with CPU0 running NEWTFILTER and CPU1 running DELFILTER:\\n\\n 0: mutex_lock() \u003c-- holds the idr lock\\n 0: rcu_read_lock()\\n 0: p = idr_find(idr, index) \u003c-- action p is valid (RCU protects IDR)\\n 0: mutex_unlock() \u003c-- releases the idr lock\\n 1: refcount_dec_and_mutex_lock() \u003c-- refcnt 1-\u003e0, mutex held\\n 1: idr_remove(idr, index) \u003c-- Action removed from IDR\\n 1: mutex_unlock() \u003c-- mutex released allowing us to delete the action\\n 1: tcf_action_cleanup(p); kfree(p) \u003c-- Kfrees p immediately, no deferral\\n 0: refcount_inc_not_zero(\u0026p-\u003etcfa_refcnt) \u003c-- ouch, UAF p points to freed memory\\n\\nThis patch fixes the race condition between NEWTFILTER and DELFILTER by\\nadding struct rcu_head to tc_action used in the deferral and introducing a\\ncall_rcu() in the delete path to defer the final kfree().\\n\\nNote: this is a revert of commit d7fb60b9cafb (\\\"net_sched: get rid of tcfa_rcu\\\")\\nbut also modernization/simplification to directly use kfree_rcu().\\n\\nLet\u0027s illustrate the new restored code path:\\n\\n 0: rcu_read_lock()\\n 1: refcount_dec_and_mutex_lock() \u003c-- refcnt 1-\u003e0, mutex held\\n 1: idr_remove(idr, index)\\n 1: mutex_unlock()\\n 1: call_rcu(\u0026p-\u003etcfa_rcu, tcf_action_rcu_free) \u003c-- defer kfree after grace period\\n 0: p = idr_find(idr, index)\\n 0: refcount_inc_not_zero(\u0026p-\u003etcfa_refcnt) \u003c-- fails, refcnt already 0\\n 1: rcu_read_unlock() \u003c-- release so freeing can run after grace period\\n\\nAfter CPU1 calls idr_remove(), the object is no longer reachable through the IDR.\\nCPU0\u0027s subsequent idr_find() will return NULL, and even if it still held a\\nstale pointer, the immediate kfree() is now deferred until after the RCU grace\\nperiod, so no UAF can occur.\"}], \"cpeApplicability\": [{\"nodes\": [{\"negate\": false, \"cpeMatch\": [{\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"5.10.259\", \"versionStartIncluding\": \"4.14\"}, {\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"5.15.210\", \"versionStartIncluding\": \"4.14\"}, {\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"6.1.176\", \"versionStartIncluding\": \"4.14\"}, {\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"6.6.143\", \"versionStartIncluding\": \"4.14\"}, {\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"6.12.94\", \"versionStartIncluding\": \"4.14\"}, {\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"6.18.36\", \"versionStartIncluding\": \"4.14\"}, {\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"7.0.13\", \"versionStartIncluding\": \"4.14\"}, {\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"7.1\", \"versionStartIncluding\": \"4.14\"}], \"operator\": \"OR\"}]}], \"providerMetadata\": {\"orgId\": \"416baaa9-dc9f-4396-8d5f-8c081fb06d67\", \"shortName\": \"Linux\", \"dateUpdated\": \"2026-08-05T12:34:41.215Z\"}}}",
"cveMetadata": "{\"cveId\": \"CVE-2026-53264\", \"state\": \"PUBLISHED\", \"dateUpdated\": \"2026-08-05T12:34:41.215Z\", \"dateReserved\": \"2026-06-09T07:44:35.395Z\", \"assignerOrgId\": \"416baaa9-dc9f-4396-8d5f-8c081fb06d67\", \"datePublished\": \"2026-06-25T08:39:51.870Z\", \"assignerShortName\": \"Linux\"}",
"dataType": "CVE_RECORD",
"dataVersion": "5.2"
}
}
}
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Sightings
| Author | Source | Type | Date |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or seen somewhere by the user.
- Confirmed: The vulnerability is confirmed from an analyst perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: This vulnerability was exploited and seen by the user reporting the sighting.
- Patched: This vulnerability was successfully patched by the user reporting the sighting.
- Not exploited: This vulnerability was not exploited or seen by the user reporting the sighting.
- Not confirmed: The user expresses doubt about the veracity of the vulnerability.
- Not patched: This vulnerability was not successfully patched by the user reporting the sighting.
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