CVE-2026-72436 (GCVE-0-2026-72436)

Vulnerability from cvelistv5 – Published: 2026-08-15 05:56 – Updated: 2026-08-17 05:44
VLAI
Title
netfilter: ipset: Don't use test_bit() in lockless RCU readers in hash types
Summary
In the Linux kernel, the following vulnerability has been resolved: netfilter: ipset: Don't use test_bit() in lockless RCU readers in hash types Sashiko pointed out that there are a few lockless RCU readers using test_bit() which is a relaxed atomic operation and provides no memory barrier guarantees. Use test_bit_acquire() instead where the operation may run parallel with add/del/gc, i.e. is not one from the next cases - protected by region lock - in a set destroy phase - in a new/temporary set creation phase
Severity
9.8 (Critical)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Assigner
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: 18f84d41d34fa35d0d64bbaea01fe664553ecc06 , < c107233d2ff4fd7cef5d02f9124b99194957a710 (git)
Affected: 18f84d41d34fa35d0d64bbaea01fe664553ecc06 , < 6329d3a9afe715fddda0460cfa46b496d61c2fe0 (git)
Affected: 18f84d41d34fa35d0d64bbaea01fe664553ecc06 , < 7445fe965b7d8756070a40e80f8b73348ccda1d7 (git)
Affected: 18f84d41d34fa35d0d64bbaea01fe664553ecc06 , < c4d257734e91bfcdc71d41843392dd6400b5bb1b (git)
Affected: 18f84d41d34fa35d0d64bbaea01fe664553ecc06 , < 3219d74e4536658c937fd878a327257b86ce80dd (git)
Affected: 18f84d41d34fa35d0d64bbaea01fe664553ecc06 , < e4b4984e28c16406ecb318444dea4a8bf47def3e (git)
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Linux Linux Affected: 4.2
Unaffected: 0 , < 4.2 (semver)
Unaffected: 6.1.178 , ≤ 6.1.* (semver)
Unaffected: 6.6.145 , ≤ 6.6.* (semver)
Unaffected: 6.12.97 , ≤ 6.12.* (semver)
Unaffected: 6.18.40 , ≤ 6.18.* (semver)
Unaffected: 7.1.5 , ≤ 7.1.* (semver)
Unaffected: 7.2 , ≤ * (original_commit_for_fix)
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{
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          "product": "Linux",
          "programFiles": [
            "net/netfilter/ipset/ip_set_hash_gen.h"
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              "version": "6.12.97",
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              "version": "7.1.5",
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            "version": "3.1"
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              "value": "AV:N - The vulnerable mtype_test() runs on every packet matched by iptables/nftables xt_set rules in PREROUTING/INPUT/FORWARD, so a remote attacker reaches the bug by sending network traffic to internet-facing servers using ipset-based firewall blocklists.\nAC:L - The attacker controls both sides of the race by flooding packets that trigger lockless RCU readers while concurrently driving hash add/del via SET target rules or timeout GC on the same ipset, making the memory-ordering race reliably winnable.\nPR:N - No credentials or local access are required on the target; exploitation needs only unauthenticated network packets to a host running ipset netfilter rules, a standard deployment on firewalls, mail servers, and CDN edge nodes.\nUI:N - No victim interaction is needed; the attack is fully automated by sending network traffic and does not require mounting filesystems, opening files, or any other user action.\nS:U - The vulnerability corrupts or leaks kernel heap data within the same host security boundary; it does not cross VM, container, or IOMMU isolation boundaries.\nC:H - Without acquire semantics, test_bit() can observe a slot as used before element writes are visible or after deletion, causing reads of uninitialized, stale, or freed hbucket element and extension memory\u2014a UAF-class kernel information disclosure.\nI:H - Stale or torn reads of hash bucket elements during concurrent add/del/gc constitute kernel heap memory safety violations that can corrupt netfilter matching decisions and be further leveraged for control-flow or data manipulation attacks.\nA:H - Reading partially initialized or post-destroy hash element memory during softirq packet processing on loaded firewall datapaths can trigger kernel oopses, panics, or hangs, causing complete loss of availability."
            }
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          "url": "https://git.kernel.org/stable/c/e4b4984e28c16406ecb318444dea4a8bf47def3e"
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    "datePublished": "2026-08-15T05:56:50.051Z",
    "dateReserved": "2026-08-09T03:40:39.929Z",
    "dateUpdated": "2026-08-17T05:44:12.018Z",
    "state": "PUBLISHED"
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    "redhat_vex": {
      "aggregate_severity": "Moderate",
      "current_release_date": "2026-08-18T09:53:24+00:00",
      "cve": "CVE-2026-72436",
      "id": "CVE-2026-72436",
      "initial_release_date": "2026-08-15T00:00:00+00:00",
      "product_status:known_affected": "274",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: netfilter: ipset: Don\u0027t use test_bit() in lockless RCU readers in hash types",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-72436.json",
      "version": "3"
    }
  }
}



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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.