CVE-2026-46319 (GCVE-0-2026-46319)
Vulnerability from cvelistv5 – Published: 2026-06-09 12:11 – Updated: 2026-06-09 12:11
VLAI
Title
net/sched: act_ct: Only release RCU read lock after ct_ft
Summary
In the Linux kernel, the following vulnerability has been resolved:
net/sched: act_ct: Only release RCU read lock after ct_ft
When looking up a flow table in act_ct in tcf_ct_flow_table_get(),
rhashtable_lookup_fast() internally opens and closes an RCU read critical
section before returning ct_ft.
The tcf_ct_flow_table_cleanup_work() can complete before refcount_inc_not_zero()
is invoked on the returned ct_ft resulting in a UAF on the already freed ct_ft
object. This vulnerability can lead to privilege escalation.
Analysis from zdi-disclosures@trendmicro.com:
When initializing act_ct, tcf_ct_init() is called, which internally triggers
tcf_ct_flow_table_get().
static int tcf_ct_flow_table_get(struct net *net, struct tcf_ct_params *params)
{
struct zones_ht_key key = { .net = net, .zone = params->zone };
struct tcf_ct_flow_table *ct_ft;
int err = -ENOMEM;
mutex_lock(&zones_mutex);
ct_ft = rhashtable_lookup_fast(&zones_ht, &key, zones_params); // [1]
if (ct_ft && refcount_inc_not_zero(&ct_ft->ref)) // [2]
goto out_unlock;
...
}
static __always_inline void *rhashtable_lookup_fast(
struct rhashtable *ht, const void *key,
const struct rhashtable_params params)
{
void *obj;
rcu_read_lock();
obj = rhashtable_lookup(ht, key, params);
rcu_read_unlock();
return obj;
}
At [1], rhashtable_lookup_fast() looks up and returns the corresponding ct_ft
from zones_ht . The lookup is performed within an RCU read critical section
through rcu_read_lock() / rcu_read_unlock(), which prevents the object from
being freed. However, at the point of function return, rcu_read_unlock() has
already been called, and there is nothing preventing ct_ft from being freed
before reaching refcount_inc_not_zero(&ct_ft->ref) at [2]. This interval becomes
the race window, during which ct_ft can be freed.
Free Process:
tcf_ct_flow_table_put() is executed through the path tcf_ct_cleanup() call_rcu()
tcf_ct_params_free_rcu() tcf_ct_params_free() tcf_ct_flow_table_put().
static void tcf_ct_flow_table_put(struct tcf_ct_flow_table *ct_ft)
{
if (refcount_dec_and_test(&ct_ft->ref)) {
rhashtable_remove_fast(&zones_ht, &ct_ft->node, zones_params);
INIT_RCU_WORK(&ct_ft->rwork, tcf_ct_flow_table_cleanup_work); // [3]
queue_rcu_work(act_ct_wq, &ct_ft->rwork);
}
}
At [3], tcf_ct_flow_table_cleanup_work() is scheduled as RCU work
static void tcf_ct_flow_table_cleanup_work(struct work_struct *work)
{
struct tcf_ct_flow_table *ct_ft;
struct flow_block *block;
ct_ft = container_of(to_rcu_work(work), struct tcf_ct_flow_table,
rwork);
nf_flow_table_free(&ct_ft->nf_ft);
block = &ct_ft->nf_ft.flow_block;
down_write(&ct_ft->nf_ft.flow_block_lock);
WARN_ON(!list_empty(&block->cb_list));
up_write(&ct_ft->nf_ft.flow_block_lock);
kfree(ct_ft); // [4]
module_put(THIS_MODULE);
}
tcf_ct_flow_table_cleanup_work() frees ct_ft at [4]. When this function executes
between [1] and [2], UAF occurs.
This race condition has a very short race window, making it generally
difficult to trigger. Therefore, to trigger the vulnerability an msleep(100) was
inserted after[1]
Severity
No CVSS data available.
Assigner
References
8 references
Impacted products
2 products
| Vendor | Product | Version | |
|---|---|---|---|
| Linux | Linux |
Affected:
138470a9b2cc2e26e6018300394afc3858a54e6a , < ece578ca61e572df96cfc80456357ebfae0b4b9e
(git)
Affected: 138470a9b2cc2e26e6018300394afc3858a54e6a , < a2e0c045c87aa252eb61412e67dd91f2c2b19f81 (git) Affected: 138470a9b2cc2e26e6018300394afc3858a54e6a , < 67c9ecc9f2575273ed1323e312881fc98ac83d6d (git) Affected: 138470a9b2cc2e26e6018300394afc3858a54e6a , < f23424a0ddadb494d4bd57056a7ca703312d3a7b (git) Affected: 138470a9b2cc2e26e6018300394afc3858a54e6a , < 17dfb67cb399b660105d9a8c6100851c0d0cdc70 (git) Affected: 138470a9b2cc2e26e6018300394afc3858a54e6a , < 4c727c6967a41b37efe0f26332ca9ec5b74785a3 (git) Affected: 138470a9b2cc2e26e6018300394afc3858a54e6a , < 3e20e1b3058e0b94638e7b931c138e840e266724 (git) Affected: 138470a9b2cc2e26e6018300394afc3858a54e6a , < f462dca0c8415bf0058d0ffa476354c4476d0f09 (git) |
|
| Linux | Linux |
Affected:
5.7
Unaffected: 0 , < 5.7 (semver) Unaffected: 5.10.258 , ≤ 5.10.* (semver) Unaffected: 5.15.209 , ≤ 5.15.* (semver) Unaffected: 6.1.175 , ≤ 6.1.* (semver) Unaffected: 6.6.141 , ≤ 6.6.* (semver) Unaffected: 6.12.91 , ≤ 6.12.* (semver) Unaffected: 6.18.33 , ≤ 6.18.* (semver) Unaffected: 7.0.10 , ≤ 7.0.* (semver) Unaffected: 7.1-rc1 , ≤ * (original_commit_for_fix) |
{
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"vendor": "Linux",
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"status": "unaffected",
"version": "5.15.209",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.1.*",
"status": "unaffected",
"version": "6.1.175",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.6.*",
"status": "unaffected",
"version": "6.6.141",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.12.*",
"status": "unaffected",
"version": "6.12.91",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.18.*",
"status": "unaffected",
"version": "6.18.33",
"versionType": "semver"
},
{
"lessThanOrEqual": "7.0.*",
"status": "unaffected",
"version": "7.0.10",
"versionType": "semver"
},
{
"lessThanOrEqual": "*",
"status": "unaffected",
"version": "7.1-rc1",
"versionType": "original_commit_for_fix"
}
]
}
],
"cpeApplicability": [
{
"nodes": [
{
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"versionEndExcluding": "5.10.258",
"versionStartIncluding": "5.7",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "5.15.209",
"versionStartIncluding": "5.7",
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},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
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"vulnerable": true
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{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
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{
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],
"negate": false,
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],
"descriptions": [
{
"lang": "en",
"value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet/sched: act_ct: Only release RCU read lock after ct_ft\n\nWhen looking up a flow table in act_ct in tcf_ct_flow_table_get(),\nrhashtable_lookup_fast() internally opens and closes an RCU read critical\nsection before returning ct_ft.\nThe tcf_ct_flow_table_cleanup_work() can complete before refcount_inc_not_zero()\nis invoked on the returned ct_ft resulting in a UAF on the already freed ct_ft\nobject. This vulnerability can lead to privilege escalation.\n\nAnalysis from zdi-disclosures@trendmicro.com:\nWhen initializing act_ct, tcf_ct_init() is called, which internally triggers\ntcf_ct_flow_table_get().\n\nstatic int tcf_ct_flow_table_get(struct net *net, struct tcf_ct_params *params)\n\n{\n struct zones_ht_key key = { .net = net, .zone = params-\u003ezone };\n struct tcf_ct_flow_table *ct_ft;\n int err = -ENOMEM;\n\n mutex_lock(\u0026zones_mutex);\n ct_ft = rhashtable_lookup_fast(\u0026zones_ht, \u0026key, zones_params); // [1]\n if (ct_ft \u0026\u0026 refcount_inc_not_zero(\u0026ct_ft-\u003eref)) // [2]\n goto out_unlock;\n ...\n}\n\nstatic __always_inline void *rhashtable_lookup_fast(\n struct rhashtable *ht, const void *key,\n const struct rhashtable_params params)\n{\n void *obj;\n\n rcu_read_lock();\n obj = rhashtable_lookup(ht, key, params);\n rcu_read_unlock();\n\n return obj;\n}\n\nAt [1], rhashtable_lookup_fast() looks up and returns the corresponding ct_ft\nfrom zones_ht . The lookup is performed within an RCU read critical section\nthrough rcu_read_lock() / rcu_read_unlock(), which prevents the object from\nbeing freed. However, at the point of function return, rcu_read_unlock() has\nalready been called, and there is nothing preventing ct_ft from being freed\nbefore reaching refcount_inc_not_zero(\u0026ct_ft-\u003eref) at [2]. This interval becomes\nthe race window, during which ct_ft can be freed.\n\nFree Process:\n\ntcf_ct_flow_table_put() is executed through the path tcf_ct_cleanup() call_rcu()\ntcf_ct_params_free_rcu() tcf_ct_params_free() tcf_ct_flow_table_put().\n\nstatic void tcf_ct_flow_table_put(struct tcf_ct_flow_table *ct_ft)\n{\n if (refcount_dec_and_test(\u0026ct_ft-\u003eref)) {\n rhashtable_remove_fast(\u0026zones_ht, \u0026ct_ft-\u003enode, zones_params);\n INIT_RCU_WORK(\u0026ct_ft-\u003erwork, tcf_ct_flow_table_cleanup_work); // [3]\n queue_rcu_work(act_ct_wq, \u0026ct_ft-\u003erwork);\n }\n}\n\nAt [3], tcf_ct_flow_table_cleanup_work() is scheduled as RCU work\n\nstatic void tcf_ct_flow_table_cleanup_work(struct work_struct *work)\n\n{\n struct tcf_ct_flow_table *ct_ft;\n struct flow_block *block;\n\n ct_ft = container_of(to_rcu_work(work), struct tcf_ct_flow_table,\n rwork);\n nf_flow_table_free(\u0026ct_ft-\u003enf_ft);\n block = \u0026ct_ft-\u003enf_ft.flow_block;\n down_write(\u0026ct_ft-\u003enf_ft.flow_block_lock);\n WARN_ON(!list_empty(\u0026block-\u003ecb_list));\n up_write(\u0026ct_ft-\u003enf_ft.flow_block_lock);\n kfree(ct_ft); // [4]\n\n module_put(THIS_MODULE);\n}\n\ntcf_ct_flow_table_cleanup_work() frees ct_ft at [4]. When this function executes\nbetween [1] and [2], UAF occurs.\n\nThis race condition has a very short race window, making it generally\ndifficult to trigger. Therefore, to trigger the vulnerability an msleep(100) was\ninserted after[1]"
}
],
"providerMetadata": {
"dateUpdated": "2026-06-09T12:11:12.128Z",
"orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"shortName": "Linux"
},
"references": [
{
"url": "https://git.kernel.org/stable/c/ece578ca61e572df96cfc80456357ebfae0b4b9e"
},
{
"url": "https://git.kernel.org/stable/c/a2e0c045c87aa252eb61412e67dd91f2c2b19f81"
},
{
"url": "https://git.kernel.org/stable/c/67c9ecc9f2575273ed1323e312881fc98ac83d6d"
},
{
"url": "https://git.kernel.org/stable/c/f23424a0ddadb494d4bd57056a7ca703312d3a7b"
},
{
"url": "https://git.kernel.org/stable/c/17dfb67cb399b660105d9a8c6100851c0d0cdc70"
},
{
"url": "https://git.kernel.org/stable/c/4c727c6967a41b37efe0f26332ca9ec5b74785a3"
},
{
"url": "https://git.kernel.org/stable/c/3e20e1b3058e0b94638e7b931c138e840e266724"
},
{
"url": "https://git.kernel.org/stable/c/f462dca0c8415bf0058d0ffa476354c4476d0f09"
}
],
"title": "net/sched: act_ct: Only release RCU read lock after ct_ft",
"x_generator": {
"engine": "bippy-1.2.0"
}
}
},
"cveMetadata": {
"assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"assignerShortName": "Linux",
"cveId": "CVE-2026-46319",
"datePublished": "2026-06-09T12:11:12.128Z",
"dateReserved": "2026-05-13T15:03:33.112Z",
"dateUpdated": "2026-06-09T12:11:12.128Z",
"state": "PUBLISHED"
},
"dataType": "CVE_RECORD",
"dataVersion": "5.2",
"vulnerability-lookup:meta": {
"epss": {
"cve": "CVE-2026-46319",
"date": "2026-06-10",
"epss": "0.00024",
"percentile": "0.0726"
},
"nvd": "{\"cve\":{\"id\":\"CVE-2026-46319\",\"sourceIdentifier\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"published\":\"2026-06-09T13:16:37.210\",\"lastModified\":\"2026-06-09T13:16:37.210\",\"vulnStatus\":\"Received\",\"cveTags\":[],\"descriptions\":[{\"lang\":\"en\",\"value\":\"In the Linux kernel, the following vulnerability has been resolved:\\n\\nnet/sched: act_ct: Only release RCU read lock after ct_ft\\n\\nWhen looking up a flow table in act_ct in tcf_ct_flow_table_get(),\\nrhashtable_lookup_fast() internally opens and closes an RCU read critical\\nsection before returning ct_ft.\\nThe tcf_ct_flow_table_cleanup_work() can complete before refcount_inc_not_zero()\\nis invoked on the returned ct_ft resulting in a UAF on the already freed ct_ft\\nobject. This vulnerability can lead to privilege escalation.\\n\\nAnalysis from zdi-disclosures@trendmicro.com:\\nWhen initializing act_ct, tcf_ct_init() is called, which internally triggers\\ntcf_ct_flow_table_get().\\n\\nstatic int tcf_ct_flow_table_get(struct net *net, struct tcf_ct_params *params)\\n\\n{\\n struct zones_ht_key key = { .net = net, .zone = params-\u003ezone };\\n struct tcf_ct_flow_table *ct_ft;\\n int err = -ENOMEM;\\n\\n mutex_lock(\u0026zones_mutex);\\n ct_ft = rhashtable_lookup_fast(\u0026zones_ht, \u0026key, zones_params); // [1]\\n if (ct_ft \u0026\u0026 refcount_inc_not_zero(\u0026ct_ft-\u003eref)) // [2]\\n goto out_unlock;\\n ...\\n}\\n\\nstatic __always_inline void *rhashtable_lookup_fast(\\n struct rhashtable *ht, const void *key,\\n const struct rhashtable_params params)\\n{\\n void *obj;\\n\\n rcu_read_lock();\\n obj = rhashtable_lookup(ht, key, params);\\n rcu_read_unlock();\\n\\n return obj;\\n}\\n\\nAt [1], rhashtable_lookup_fast() looks up and returns the corresponding ct_ft\\nfrom zones_ht . The lookup is performed within an RCU read critical section\\nthrough rcu_read_lock() / rcu_read_unlock(), which prevents the object from\\nbeing freed. However, at the point of function return, rcu_read_unlock() has\\nalready been called, and there is nothing preventing ct_ft from being freed\\nbefore reaching refcount_inc_not_zero(\u0026ct_ft-\u003eref) at [2]. This interval becomes\\nthe race window, during which ct_ft can be freed.\\n\\nFree Process:\\n\\ntcf_ct_flow_table_put() is executed through the path tcf_ct_cleanup() call_rcu()\\ntcf_ct_params_free_rcu() tcf_ct_params_free() tcf_ct_flow_table_put().\\n\\nstatic void tcf_ct_flow_table_put(struct tcf_ct_flow_table *ct_ft)\\n{\\n if (refcount_dec_and_test(\u0026ct_ft-\u003eref)) {\\n rhashtable_remove_fast(\u0026zones_ht, \u0026ct_ft-\u003enode, zones_params);\\n INIT_RCU_WORK(\u0026ct_ft-\u003erwork, tcf_ct_flow_table_cleanup_work); // [3]\\n queue_rcu_work(act_ct_wq, \u0026ct_ft-\u003erwork);\\n }\\n}\\n\\nAt [3], tcf_ct_flow_table_cleanup_work() is scheduled as RCU work\\n\\nstatic void tcf_ct_flow_table_cleanup_work(struct work_struct *work)\\n\\n{\\n struct tcf_ct_flow_table *ct_ft;\\n struct flow_block *block;\\n\\n ct_ft = container_of(to_rcu_work(work), struct tcf_ct_flow_table,\\n rwork);\\n nf_flow_table_free(\u0026ct_ft-\u003enf_ft);\\n block = \u0026ct_ft-\u003enf_ft.flow_block;\\n down_write(\u0026ct_ft-\u003enf_ft.flow_block_lock);\\n WARN_ON(!list_empty(\u0026block-\u003ecb_list));\\n up_write(\u0026ct_ft-\u003enf_ft.flow_block_lock);\\n kfree(ct_ft); // [4]\\n\\n module_put(THIS_MODULE);\\n}\\n\\ntcf_ct_flow_table_cleanup_work() frees ct_ft at [4]. When this function executes\\nbetween [1] and [2], UAF occurs.\\n\\nThis race condition has a very short race window, making it generally\\ndifficult to trigger. Therefore, to trigger the vulnerability an msleep(100) was\\ninserted after[1]\"}],\"metrics\":{},\"references\":[{\"url\":\"https://git.kernel.org/stable/c/17dfb67cb399b660105d9a8c6100851c0d0cdc70\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/3e20e1b3058e0b94638e7b931c138e840e266724\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/4c727c6967a41b37efe0f26332ca9ec5b74785a3\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/67c9ecc9f2575273ed1323e312881fc98ac83d6d\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/a2e0c045c87aa252eb61412e67dd91f2c2b19f81\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/ece578ca61e572df96cfc80456357ebfae0b4b9e\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/f23424a0ddadb494d4bd57056a7ca703312d3a7b\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/f462dca0c8415bf0058d0ffa476354c4476d0f09\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"}]}}"
}
}
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Experimental. This forecast is provided for visualization only and may change without notice. Do not use it for operational decisions.
Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.
Sightings
| Author | Source | Type | Date | Other |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or observed by the user.
- Confirmed: The vulnerability has been validated from an analyst's perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
- Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
- Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
- Not confirmed: The user expressed doubt about the validity of the vulnerability.
- Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.
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