CVE-2021-46913 (GCVE-0-2021-46913)
Vulnerability from cvelistv5 – Published: 2024-02-27 06:53 – Updated: 2026-08-05 08:45
VLAI
EPSS
VEX
Title
netfilter: nftables: clone set element expression template
Summary
In the Linux kernel, the following vulnerability has been resolved:
netfilter: nftables: clone set element expression template
memcpy() breaks when using connlimit in set elements. Use
nft_expr_clone() to initialize the connlimit expression list, otherwise
connlimit garbage collector crashes when walking on the list head copy.
[ 493.064656] Workqueue: events_power_efficient nft_rhash_gc [nf_tables]
[ 493.064685] RIP: 0010:find_or_evict+0x5a/0x90 [nf_conncount]
[ 493.064694] Code: 2b 43 40 83 f8 01 77 0d 48 c7 c0 f5 ff ff ff 44 39 63 3c 75 df 83 6d 18 01 48 8b 43 08 48 89 de 48 8b 13 48 8b 3d ee 2f 00 00 <48> 89 42 08 48 89 10 48 b8 00 01 00 00 00 00 ad de 48 89 03 48 83
[ 493.064699] RSP: 0018:ffffc90000417dc0 EFLAGS: 00010297
[ 493.064704] RAX: 0000000000000000 RBX: ffff888134f38410 RCX: 0000000000000000
[ 493.064708] RDX: 0000000000000000 RSI: ffff888134f38410 RDI: ffff888100060cc0
[ 493.064711] RBP: ffff88812ce594a8 R08: ffff888134f38438 R09: 00000000ebb9025c
[ 493.064714] R10: ffffffff8219f838 R11: 0000000000000017 R12: 0000000000000001
[ 493.064718] R13: ffffffff82146740 R14: ffff888134f38410 R15: 0000000000000000
[ 493.064721] FS: 0000000000000000(0000) GS:ffff88840e440000(0000) knlGS:0000000000000000
[ 493.064725] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 493.064729] CR2: 0000000000000008 CR3: 00000001330aa002 CR4: 00000000001706e0
[ 493.064733] Call Trace:
[ 493.064737] nf_conncount_gc_list+0x8f/0x150 [nf_conncount]
[ 493.064746] nft_rhash_gc+0x106/0x390 [nf_tables]
Severity
7.8 (High)
SSVC
Exploitation: none
Automatable: no
Technical Impact: partial
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2024-07-25 16:05 UTC
Assigner
References
Impacted products
2 products
| Vendor | Product | Version | CPE status | |
|---|---|---|---|---|
| Linux | Linux |
Affected:
4094445229760d0d31a4190dfe88fe815c9fc34e , < e51ff3ffc316377cca21de8b80404eed0c37b3c3
(git)
Affected: 4094445229760d0d31a4190dfe88fe815c9fc34e , < 47d8de3c226574a3ddb8b87d0c152028d1bafef4 (git) Affected: 4094445229760d0d31a4190dfe88fe815c9fc34e , < 4d8f9065830e526c83199186c5f56a6514f457d2 (git) |
guessed | |
| Linux | Linux |
Affected:
5.7
Unaffected: 0 , < 5.7 (semver) Unaffected: 5.10.64 , ≤ 5.10.* (semver) Unaffected: 5.11.16 , ≤ 5.11.* (semver) Unaffected: 5.12 , ≤ * (original_commit_for_fix) |
guessed |
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"value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnetfilter: nftables: clone set element expression template\n\nmemcpy() breaks when using connlimit in set elements. Use\nnft_expr_clone() to initialize the connlimit expression list, otherwise\nconnlimit garbage collector crashes when walking on the list head copy.\n\n[ 493.064656] Workqueue: events_power_efficient nft_rhash_gc [nf_tables]\n[ 493.064685] RIP: 0010:find_or_evict+0x5a/0x90 [nf_conncount]\n[ 493.064694] Code: 2b 43 40 83 f8 01 77 0d 48 c7 c0 f5 ff ff ff 44 39 63 3c 75 df 83 6d 18 01 48 8b 43 08 48 89 de 48 8b 13 48 8b 3d ee 2f 00 00 \u003c48\u003e 89 42 08 48 89 10 48 b8 00 01 00 00 00 00 ad de 48 89 03 48 83\n[ 493.064699] RSP: 0018:ffffc90000417dc0 EFLAGS: 00010297\n[ 493.064704] RAX: 0000000000000000 RBX: ffff888134f38410 RCX: 0000000000000000\n[ 493.064708] RDX: 0000000000000000 RSI: ffff888134f38410 RDI: ffff888100060cc0\n[ 493.064711] RBP: ffff88812ce594a8 R08: ffff888134f38438 R09: 00000000ebb9025c\n[ 493.064714] R10: ffffffff8219f838 R11: 0000000000000017 R12: 0000000000000001\n[ 493.064718] R13: ffffffff82146740 R14: ffff888134f38410 R15: 0000000000000000\n[ 493.064721] FS: 0000000000000000(0000) GS:ffff88840e440000(0000) knlGS:0000000000000000\n[ 493.064725] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033\n[ 493.064729] CR2: 0000000000000008 CR3: 00000001330aa002 CR4: 00000000001706e0\n[ 493.064733] Call Trace:\n[ 493.064737] nf_conncount_gc_list+0x8f/0x150 [nf_conncount]\n[ 493.064746] nft_rhash_gc+0x106/0x390 [nf_tables]"
},
{
"lang": "es",
"value": "En el kernel de Linux, se ha resuelto la siguiente vulnerabilidad: netfilter: nftables: clonar la plantilla de expresi\u00f3n de elementos establecidos memcpy() se rompe cuando se usa connlimit en elementos establecidos. Utilice nft_expr_clone() para inicializar la lista de expresiones connlimit; de lo contrario, el recolector de basura connlimit se bloquea al caminar sobre la copia del encabezado de la lista. [ 493.064656] Cola de trabajo: events_power_ficient nft_rhash_gc [nf_tables] [ 493.064685] RIP: 0010:find_or_evict+0x5a/0x90 [nf_conncount] [ 493.064694] C\u00f3digo: 2b 43 40 83 f8 01 77 0d 48 c7 c0 f5 ff ff ff 44 39 63 3c 75 df 83 6d 18 01 48 8b 43 08 48 89 de 48 8b 13 48 8b 3d ee 2f 00 00 \u0026lt;48\u0026gt; 89 42 08 48 89 10 48 b8 00 01 00 00 00 00 ad de 48 89 03 48 83 [ 493.064699] RSP : 0018:ffffc90000417dc0 EFLAGS: 00010297 [ 493.064704] RAX: 0000000000000000 RBX: ffff888134f38410 RCX: 00000000000000000 [ 493.064708] RDX: 0000000000000000 RSI: ffff888134f38410 RDI: ffff888100060cc0 [ 493.064711] RBP: ffff88812ce594a8 R08: ffff888134f38438 R09: 00000000ebb9025c [ 49 3.064714] R10: ffffffff8219f838 R11 : 0000000000000017 R12: 0000000000000001 [ 493.064718] R13: ffffffff82146740 R14: ffff888134f38410 R15: 0000000000000000 [ 493.064721] FS : 0000000000000000(0000) GS:ffff88840e440000(0000) knlGS:0000000000000000 [ 493.064725] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 493.064729] CR2: 0000000000000008 CR3: 00000001330aa002 CR4: 00000000001706e0 [ 493.064733] Seguimiento de llamadas: [ 493.064737] nf_conncount_gc_list+0x8f/0x15 0 [nf_conncount] [493.064746] nft_rhash_gc+0x106/0x390 [nf_tables]"
}
],
"id": "CVE-2021-46913",
"lastModified": "2026-08-04T10:16:36.373",
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"scope": "UNCHANGED",
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"scope": "UNCHANGED",
"userInteraction": "NONE",
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"version": "3.1"
},
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"timestamp": "2024-07-25T16:05:03.441249Z",
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"value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnetfilter: nftables: clone set element expression template\n\nmemcpy() breaks when using connlimit in set elements. Use\nnft_expr_clone() to initialize the connlimit expression list, otherwise\nconnlimit garbage collector crashes when walking on the list head copy.\n\n[ 493.064656] Workqueue: events_power_efficient nft_rhash_gc [nf_tables]\n[ 493.064685] RIP: 0010:find_or_evict+0x5a/0x90 [nf_conncount]\n[ 493.064694] Code: 2b 43 40 83 f8 01 77 0d 48 c7 c0 f5 ff ff ff 44 39 63 3c 75 df 83 6d 18 01 48 8b 43 08 48 89 de 48 8b 13 48 8b 3d ee 2f 00 00 \u003c48\u003e 89 42 08 48 89 10 48 b8 00 01 00 00 00 00 ad de 48 89 03 48 83\n[ 493.064699] RSP: 0018:ffffc90000417dc0 EFLAGS: 00010297\n[ 493.064704] RAX: 0000000000000000 RBX: ffff888134f38410 RCX: 0000000000000000\n[ 493.064708] RDX: 0000000000000000 RSI: ffff888134f38410 RDI: ffff888100060cc0\n[ 493.064711] RBP: ffff88812ce594a8 R08: ffff888134f38438 R09: 00000000ebb9025c\n[ 493.064714] R10: ffffffff8219f838 R11: 0000000000000017 R12: 0000000000000001\n[ 493.064718] R13: ffffffff82146740 R14: ffff888134f38410 R15: 0000000000000000\n[ 493.064721] FS: 0000000000000000(0000) GS:ffff88840e440000(0000) knlGS:0000000000000000\n[ 493.064725] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033\n[ 493.064729] CR2: 0000000000000008 CR3: 00000001330aa002 CR4: 00000000001706e0\n[ 493.064733] Call Trace:\n[ 493.064737] nf_conncount_gc_list+0x8f/0x150 [nf_conncount]\n[ 493.064746] nft_rhash_gc+0x106/0x390 [nf_tables]"
}
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"value": "AV:L - The bug is reached only via nfnetlink NFT_MSG_NEWSETELEM configuration of nftables set elements with stateful expressions (connlimit), which requires a local netlink socket rather than remote packet processing.\nAC:L - An attacker can reliably create a set with a connlimit expression, add elements so memcpy leaves a dangling list_head, then trigger the corruption via the scheduled nft_rhash_gc work, packet eval (nf_conncount_add), or set teardown\u2014no conditions beyond attacker control.\nPR:L - nfnetlink requires CAP_NET_ADMIN via netlink_net_capable, but that capability is obtainable in an unprivileged user namespace (unshare -Urn), so nftables is reachable as an unprivileged local user.\nUI:N - Exploitation needs no victim action; the attacker configures nftables and can trigger GC/eval/destroy themselves.\nS:U - This is a standard kernel memory-corruption privilege-escalation path within the same host authority; it does not cross VM/IOMMU/sandbox boundaries.\nC:H - memcpy of the connlimit expression copies list_head pointers, then kfree of the source creates a UAF; with heap spray that UAF yields forged list nodes and arbitrary kernel memory read primitives.\nI:H - Walking or deleting entries on the corrupted/UAF\u0027d nf_conncount list (list_del in find_or_evict/conn_free) provides a classic arbitrary kernel write usable for control-flow hijacking.\nA:H - The reported oops in find_or_evict during nft_rhash_gc (NULL write via corrupted list_del) is a reliable kernel crash/DoS, and UAFs remain crash-prone even when not fully exploited."
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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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The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the
vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base
model, served locally by ML-Gateway.
They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.
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Related by attack behaviour
Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.
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