CVE-2026-23351 (GCVE-0-2026-23351)

Vulnerability from cvelistv5 – Published: 2026-03-25 10:27 – Updated: 2026-04-02 14:44
VLAI?
Title
netfilter: nft_set_pipapo: split gc into unlink and reclaim phase
Summary
In the Linux kernel, the following vulnerability has been resolved: netfilter: nft_set_pipapo: split gc into unlink and reclaim phase Yiming Qian reports Use-after-free in the pipapo set type: Under a large number of expired elements, commit-time GC can run for a very long time in a non-preemptible context, triggering soft lockup warnings and RCU stall reports (local denial of service). We must split GC in an unlink and a reclaim phase. We cannot queue elements for freeing until pointers have been swapped. Expired elements are still exposed to both the packet path and userspace dumpers via the live copy of the data structure. call_rcu() does not protect us: dump operations or element lookups starting after call_rcu has fired can still observe the free'd element, unless the commit phase has made enough progress to swap the clone and live pointers before any new reader has picked up the old version. This a similar approach as done recently for the rbtree backend in commit 35f83a75529a ("netfilter: nft_set_rbtree: don't gc elements on insert").
Severity ?
7.8 (High)
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Assigner
References
Impacted products
Vendor Product Version
Linux Linux Affected: 3c4287f62044a90e73a561aa05fc46e62da173da , < 16f3595c0441d87dfa005c47d8f95be213afaa9e (git)
Affected: 3c4287f62044a90e73a561aa05fc46e62da173da , < 7864c667aed01a58b87ca518a631322cd0ac34c0 (git)
Affected: 3c4287f62044a90e73a561aa05fc46e62da173da , < c12d570d71920903a1a0468b7d13b085203d0c93 (git)
Affected: 3c4287f62044a90e73a561aa05fc46e62da173da , < 500a50a301ce962b019ab95053ac70264fec2c21 (git)
Affected: 3c4287f62044a90e73a561aa05fc46e62da173da , < aff13667708dfa0dce136b8efd81baa9fa6ef261 (git)
Affected: 3c4287f62044a90e73a561aa05fc46e62da173da , < 9df95785d3d8302f7c066050117b04cd3c2048c2 (git)
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    Linux Linux Affected: 5.6
Unaffected: 0 , < 5.6 (semver)
Unaffected: 6.1.167 , ≤ 6.1.* (semver)
Unaffected: 6.6.130 , ≤ 6.6.* (semver)
Unaffected: 6.12.77 , ≤ 6.12.* (semver)
Unaffected: 6.18.17 , ≤ 6.18.* (semver)
Unaffected: 6.19.7 , ≤ 6.19.* (semver)
Unaffected: 7.0-rc3 , ≤ * (original_commit_for_fix)
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          "product": "Linux",
          "programFiles": [
            "include/net/netfilter/nf_tables.h",
            "net/netfilter/nf_tables_api.c",
            "net/netfilter/nft_set_pipapo.c",
            "net/netfilter/nft_set_pipapo.h"
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          "programFiles": [
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        }
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    "datePublished": "2026-03-25T10:27:36.854Z",
    "dateReserved": "2026-01-13T15:37:45.999Z",
    "dateUpdated": "2026-04-02T14:44:21.072Z",
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    "nvd": "{\"cve\":{\"id\":\"CVE-2026-23351\",\"sourceIdentifier\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"published\":\"2026-03-25T11:16:33.450\",\"lastModified\":\"2026-04-02T15:16:31.790\",\"vulnStatus\":\"Awaiting Analysis\",\"cveTags\":[],\"descriptions\":[{\"lang\":\"en\",\"value\":\"In the Linux kernel, the following vulnerability has been resolved:\\n\\nnetfilter: nft_set_pipapo: split gc into unlink and reclaim phase\\n\\nYiming Qian reports Use-after-free in the pipapo set type:\\n  Under a large number of expired elements, commit-time GC can run for a very\\n  long time in a non-preemptible context, triggering soft lockup warnings and\\n  RCU stall reports (local denial of service).\\n\\nWe must split GC in an unlink and a reclaim phase.\\n\\nWe cannot queue elements for freeing until pointers have been swapped.\\nExpired elements are still exposed to both the packet path and userspace\\ndumpers via the live copy of the data structure.\\n\\ncall_rcu() does not protect us: dump operations or element lookups starting\\nafter call_rcu has fired can still observe the free\u0027d element, unless the\\ncommit phase has made enough progress to swap the clone and live pointers\\nbefore any new reader has picked up the old version.\\n\\nThis a similar approach as done recently for the rbtree backend in commit\\n35f83a75529a (\\\"netfilter: nft_set_rbtree: don\u0027t gc elements on insert\\\").\"},{\"lang\":\"es\",\"value\":\"En el kernel de Linux, la siguiente vulnerabilidad ha sido resuelta:\\n\\nnetfilter: nft_set_pipapo: dividir la recolecci\u00f3n de basura en una fase de desvinculaci\u00f3n y una fase de recuperaci\u00f3n\\n\\nYiming Qian informa de un uso despu\u00e9s de liberaci\u00f3n en el tipo de conjunto pipapo:\\nBajo un gran n\u00famero de elementos caducados, la recolecci\u00f3n de basura en tiempo de commit puede ejecutarse durante mucho tiempo en un contexto no preemptivo, lo que desencadena advertencias de soft lockup e informes de bloqueo de RCU (denegaci\u00f3n de servicio local).\\n\\nDebemos dividir la recolecci\u00f3n de basura en una fase de desvinculaci\u00f3n y una de recuperaci\u00f3n.\\n\\nNo podemos poner en cola elementos para su liberaci\u00f3n hasta que los punteros hayan sido intercambiados.\\nLos elementos caducados todav\u00eda est\u00e1n expuestos tanto a la ruta de paquetes como a los volcadores del espacio de usuario a trav\u00e9s de la copia activa de la estructura de datos.\\n\\ncall_rcu() no nos protege: las operaciones de volcado o las b\u00fasquedas de elementos que comienzan despu\u00e9s de que call_rcu se haya activado a\u00fan pueden observar el elemento liberado, a menos que la fase de commit haya progresado lo suficiente como para intercambiar los punteros de clonaci\u00f3n y activos antes de que cualquier nuevo lector haya tomado la versi\u00f3n antigua.\\n\\nEste es un enfoque similar al realizado recientemente para el backend rbtree en el commit 35f83a75529a (\u0027netfilter: nft_set_rbtree: no recolectar elementos en la inserci\u00f3n\u0027).\"}],\"metrics\":{\"cvssMetricV31\":[{\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"type\":\"Secondary\",\"cvssData\":{\"version\":\"3.1\",\"vectorString\":\"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H\",\"baseScore\":7.8,\"baseSeverity\":\"HIGH\",\"attackVector\":\"LOCAL\",\"attackComplexity\":\"LOW\",\"privilegesRequired\":\"LOW\",\"userInteraction\":\"NONE\",\"scope\":\"UNCHANGED\",\"confidentialityImpact\":\"HIGH\",\"integrityImpact\":\"HIGH\",\"availabilityImpact\":\"HIGH\"},\"exploitabilityScore\":1.8,\"impactScore\":5.9}]},\"references\":[{\"url\":\"https://git.kernel.org/stable/c/16f3595c0441d87dfa005c47d8f95be213afaa9e\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/500a50a301ce962b019ab95053ac70264fec2c21\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/7864c667aed01a58b87ca518a631322cd0ac34c0\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/9df95785d3d8302f7c066050117b04cd3c2048c2\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/aff13667708dfa0dce136b8efd81baa9fa6ef261\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/c12d570d71920903a1a0468b7d13b085203d0c93\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"}]}}"
  }
}


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  • 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.
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