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CVE-2025-21763 (GCVE-0-2025-21763)

Vulnerability from cvelistv5 – Published: 2025-02-27 02:18 – Updated: 2026-08-05 11:54
VLAI
Title
neighbour: use RCU protection in __neigh_notify()
Summary
In the Linux kernel, the following vulnerability has been resolved: neighbour: use RCU protection in __neigh_notify() __neigh_notify() can be called without RTNL or RCU protection. Use RCU protection to avoid potential UAF.
Severity
7.8 (High)
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
SSVC
Exploitation: none Automatable: no Technical Impact: total
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2025-02-27 17:57 UTC
CWE
Assigner
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: 426b5303eb435d98b9bee37a807be386bc2b3320 , < e1aed6be381bcd7f46d4ca9d7ef0f5f3d6a1be32 (git)
Affected: 426b5303eb435d98b9bee37a807be386bc2b3320 , < 8666e9aab801328c1408a19fbf4070609dc0695a (git)
Affected: 426b5303eb435d98b9bee37a807be386bc2b3320 , < 40d8f2f2a373b6c294ffac394d2bb814b572ead1 (git)
Affected: 426b5303eb435d98b9bee37a807be386bc2b3320 , < 784eb2376270e086f7db136d154b8404edacf97b (git)
Affected: 426b5303eb435d98b9bee37a807be386bc2b3320 , < 1cbb2aa90cd3fba15ad7efb5cdda28f3d1082379 (git)
Affected: 426b5303eb435d98b9bee37a807be386bc2b3320 , < cdd5c2a12ddad8a77ce1838ff9f29aa587de82df (git)
Affected: 426b5303eb435d98b9bee37a807be386bc2b3320 , < 559307d25235e24b5424778c7332451b6c741159 (git)
Affected: 426b5303eb435d98b9bee37a807be386bc2b3320 , < becbd5850c03ed33b232083dd66c6e38c0c0e569 (git)
guessed Create a notification for this product.
Linux Linux Affected: 2.6.25
Unaffected: 0 , < 2.6.25 (semver)
Unaffected: 5.4.291 , ≤ 5.4.* (semver)
Unaffected: 5.10.235 , ≤ 5.10.* (semver)
Unaffected: 5.15.179 , ≤ 5.15.* (semver)
Unaffected: 6.1.129 , ≤ 6.1.* (semver)
Unaffected: 6.6.79 , ≤ 6.6.* (semver)
Unaffected: 6.12.16 , ≤ 6.12.* (semver)
Unaffected: 6.13.4 , ≤ 6.13.* (semver)
Unaffected: 6.14 , ≤ * (original_commit_for_fix)
guessed Create a notification for this product.
Siemens SIMATIC S7-1500 TM MFP - GNU/Linux subsystem Affected: 0 , < * (custom)
guessed Create a notification for this product.
Show details on NVD website
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    "redhat_vex": {
      "aggregate_severity": "Moderate",
      "current_release_date": "2026-06-29T23:59:11+00:00",
      "cve": "CVE-2025-21763",
      "id": "CVE-2025-21763",
      "initial_release_date": "2025-02-27T00:00:00+00:00",
      "product_status:known_affected": "274",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: neighbour: use RCU protection in __neigh_notify()",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2025/cve-2025-21763.json",
      "version": "3"
    },
    "vulnrichment": {
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A purely remote or adjacent peer can generate ARP/NDISC traffic to reach `__neigh_notify()` but cannot cause the namespace pointer to go stale.\\nAC:L - The attacker controls both sides: they spin a loop creating/destroying network namespaces with veth devices while concurrently driving neighbour add/update/GC notifications on other CPUs, so the race is created rather than waited for. Per race-condition guidance, attacker-created races are Low even though the window between the `dev_net()` load and the `net-\u003ertnl` dereference is narrow.\\nPR:L - `unshare -Urn` grants namespace-relative CAP_NET_ADMIN (`ns_capable(net-\u003euser_ns, CAP_NET_ADMIN)`), letting an ordinary unprivileged user create netns, create and move veth pairs, and trigger the teardown path; no real root is needed. Neighbour-table activity that reaches `__neigh_notify()` is likewise available to any unprivileged process.\\nUI:N - The attacker triggers both the namespace teardown and the neighbour notifications entirely from their own processes. No victim action, mount, or file open is involved.\\nS:U - The use-after-free and its consequences are confined to kernel memory within the same security authority; no VM, IOMMU, or sandbox boundary is crossed. This is standard in-kernel corruption leading to local privilege escalation.\\nC:H - The freed `struct net` is a reclaimable `net_cachep` slab object, and `net-\u003ertnl` is subsequently consumed as a `struct sock *` by `netlink_set_err()`/`nlmsg_notify()`, which read `sk-\u003esk_protocol` and `sock_net(sk)` and walk netlink tables from it. Heap-spraying the freed object turns this into an attacker-directed kernel read primitive.\\nI:H - With the freed `struct net` reclaimed under attacker control, `netlink_set_err()` writes through the forged `sk` pointer (`sk-\u003esk_err = err`, list/waitqueue manipulation), giving a controlled kernel write usable for control-flow hijacking. Per guidance, use-after-free is scored High for integrity.\\nA:H - Even without successful reclaim, dereferencing the freed `struct net` and the dangling `net-\u003ertnl` socket causes a kernel oops or panic in `nlmsg_notify()`/`netlink_set_err()`. 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      "cveMetadata": "{\"cveId\": \"CVE-2025-21763\", \"state\": \"PUBLISHED\", \"dateUpdated\": \"2026-08-05T11:54:16.348Z\", \"dateReserved\": \"2024-12-29T08:45:45.761Z\", \"assignerOrgId\": \"416baaa9-dc9f-4396-8d5f-8c081fb06d67\", \"datePublished\": \"2025-02-27T02:18:15.078Z\", \"assignerShortName\": \"Linux\"}",
      "dataType": "CVE_RECORD",
      "dataVersion": "5.2"
    }
  }
}



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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

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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.


Detection rules are retrieved from Rulezet.


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.