CVE-2026-68323 (GCVE-0-2026-68323)

Vulnerability from cvelistv5 – Published: 2026-08-10 12:02 – Updated: 2026-08-17 05:03
VLAI
Title
tipc: serialize udp bearer replicast list updates
Summary
In the Linux kernel, the following vulnerability has been resolved: tipc: serialize udp bearer replicast list updates tipc_udp_rcast_add() and cleanup_bearer() both update ub->rcast.list with list_add_rcu() / list_del_rcu(), but nothing serializes them. The add runs from the encap receive softirq (via tipc_udp_rcast_disc()) without rtnl_lock(), so it can race the cleanup delete and corrupt the list: list_del corruption. prev->next should be ffff8880298d7ab8, but was ffff88802449ad38. (prev=ffff888027e3ec98) kernel BUG at lib/list_debug.c:62! RIP: __list_del_entry_valid_or_report+0x17a/0x200 Workqueue: events cleanup_bearer Call Trace: cleanup_bearer (net/tipc/udp_media.c:811) process_one_work (kernel/workqueue.c:3302) worker_thread (kernel/workqueue.c:3466) The bearer can be enabled from an unprivileged user namespace, as the TIPCv2 generic-netlink ops carry no GENL_ADMIN_PERM. Add a spinlock to struct udp_bearer and take it around the list_add_rcu() in tipc_udp_rcast_add() and the list_del_rcu() loop in cleanup_bearer() so the two writers can no longer corrupt the list. Reject a duplicate peer under the same lock before allocating, and remove tipc_udp_is_known_peer(). The old lockless pre-check in tipc_udp_rcast_disc() was racy: two softirqs discovering the same peer could both find it absent and add it twice. cleanup_bearer() runs from a workqueue after tipc_udp_disable() clears the bearer's up bit, so an encap softirq can still reach tipc_udp_rcast_add() and add a peer after cleanup_bearer() has already emptied the list, leaking that entry when the bearer is freed. Mark the bearer disabled under rcast_lock once the list is emptied and refuse further additions.
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 CPE status
Linux Linux Affected: ef20cd4dd1633987bcf46ac34ace2c8af212361f , < d70c81001df9320d3445e664428a1d408b5ba896 (git)
Affected: ef20cd4dd1633987bcf46ac34ace2c8af212361f , < 350e592ff4e30e48ffb55e142d11a73e63f4869c (git)
guessed Create a notification for this product.
Linux Linux Affected: 4.9
Unaffected: 0 , < 4.9 (semver)
Unaffected: 7.1.6 , ≤ 7.1.* (semver)
Unaffected: 7.2 , ≤ * (original_commit_for_fix)
guessed Create a notification for this product.
Show details on NVD website
To clipboard 

{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "net/tipc/udp_media.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "d70c81001df9320d3445e664428a1d408b5ba896",
              "status": "affected",
              "version": "ef20cd4dd1633987bcf46ac34ace2c8af212361f",
              "versionType": "git"
            },
            {
              "lessThan": "350e592ff4e30e48ffb55e142d11a73e63f4869c",
              "status": "affected",
              "version": "ef20cd4dd1633987bcf46ac34ace2c8af212361f",
              "versionType": "git"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "net/tipc/udp_media.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "4.9"
            },
            {
              "lessThan": "4.9",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "7.1.*",
              "status": "unaffected",
              "version": "7.1.6",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.2",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
            {
              "cpeMatch": [
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.1.6",
                  "versionStartIncluding": "4.9",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.2",
                  "versionStartIncluding": "4.9",
                  "vulnerable": true
                }
              ],
              "negate": false,
              "operator": "OR"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\ntipc: serialize udp bearer replicast list updates\n\ntipc_udp_rcast_add() and cleanup_bearer() both update ub-\u003ercast.list with\nlist_add_rcu() / list_del_rcu(), but nothing serializes them. The add runs\nfrom the encap receive softirq (via tipc_udp_rcast_disc()) without\nrtnl_lock(), so it can race the cleanup delete and corrupt the list:\n\n  list_del corruption. prev-\u003enext should be ffff8880298d7ab8,\n    but was ffff88802449ad38. (prev=ffff888027e3ec98)\n  kernel BUG at lib/list_debug.c:62!\n  RIP: __list_del_entry_valid_or_report+0x17a/0x200\n  Workqueue: events cleanup_bearer\n  Call Trace:\n   cleanup_bearer (net/tipc/udp_media.c:811)\n   process_one_work (kernel/workqueue.c:3302)\n   worker_thread (kernel/workqueue.c:3466)\n\nThe bearer can be enabled from an unprivileged user namespace, as the\nTIPCv2 generic-netlink ops carry no GENL_ADMIN_PERM.\n\nAdd a spinlock to struct udp_bearer and take it around the list_add_rcu()\nin tipc_udp_rcast_add() and the list_del_rcu() loop in cleanup_bearer() so\nthe two writers can no longer corrupt the list.\n\nReject a duplicate peer under the same lock before allocating, and remove\ntipc_udp_is_known_peer(). The old lockless pre-check in\ntipc_udp_rcast_disc() was racy: two softirqs discovering the same peer\ncould both find it absent and add it twice.\n\ncleanup_bearer() runs from a workqueue after tipc_udp_disable() clears the\nbearer\u0027s up bit, so an encap softirq can still reach tipc_udp_rcast_add()\nand add a peer after cleanup_bearer() has already emptied the list, leaking\nthat entry when the bearer is freed. Mark the bearer disabled under\nrcast_lock once the list is emptied and refuse further additions."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "baseScore": 7.8,
            "baseSeverity": "HIGH",
            "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
            "version": "3.1"
          },
          "scenarios": [
            {
              "lang": "en",
              "value": "AV:L - Exploitation requires the local half of the race \u2014 enabling and then disabling a TIPC UDP replicast bearer via generic netlink \u2014 even though the second half is driven by UDP packets; a purely remote peer cannot schedule cleanup_bearer(), so local access is needed.\nAC:L - The attacker owns both racers: they flood LINK_CONFIG UDP packets at the bearer port (softirq list_add_rcu) while issuing TIPC_NL_BEARER_DISABLE (workqueue list_del_rcu), and the window is wide because b-\u003eup is cleared before cleanup_bearer is scheduled, so it can be retried until it hits.\nPR:L - TIPC_NL_BEARER_ENABLE/DISABLE/ADD use GENL_UNS_ADMIN_PERM, i.e. CAP_NET_ADMIN in the net\u0027s owning user namespace, which any unprivileged user obtains with unshare -Urn; no real root is required.\nUI:N - The attacker performs every step itself \u2014 create netns, enable bearer, send packets, disable bearer \u2014 with no action by any other user or administrator.\nS:U - The corruption and any resulting escalation stay within the kernel\u0027s own security authority; no VM, IOMMU, or sandbox boundary is crossed.\nC:H - Concurrent list_add_rcu/list_del_rcu on ub-\u003ercast.list leaves dangling and duplicated entries, so udp_replicast objects freed by rcast_free_rcu remain reachable from the list; the resulting use-after-free reads of attacker-groomed heap memory can disclose arbitrary kernel data.\nI:H - List corruption makes list_add_rcu/list_del_rcu write prev-\u003enext and next-\u003eprev through stale pointers into freed or attacker-controlled heap memory, a classic write primitive that is leverageable for control-flow hijack and privilege escalation.\nA:H - The reported symptom is a hard kernel BUG at lib/list_debug.c:62 (__list_del_entry_valid_or_report) in the cleanup_bearer workqueue, i.e. an immediate panic; without CONFIG_DEBUG_LIST the corrupted list and freed-entry traversal crash the kernel anyway."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-08-17T05:03:21.092Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/d70c81001df9320d3445e664428a1d408b5ba896"
        },
        {
          "url": "https://git.kernel.org/stable/c/350e592ff4e30e48ffb55e142d11a73e63f4869c"
        }
      ],
      "title": "tipc: serialize udp bearer replicast list updates",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-68323",
    "datePublished": "2026-08-10T12:02:59.034Z",
    "dateReserved": "2026-07-30T09:28:09.382Z",
    "dateUpdated": "2026-08-17T05:03:21.092Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2",
  "vulnerability-lookup:meta": {
    "epss": {
      "cve": "CVE-2026-68323",
      "date": "2026-08-20",
      "epss": "0.0012",
      "percentile": "0.02193"
    },
    "nvd": "{\"cve\":{\"id\":\"CVE-2026-68323\",\"sourceIdentifier\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"published\":\"2026-08-10T13:20:22.443\",\"lastModified\":\"2026-08-17T05:18:35.267\",\"vulnStatus\":\"Received\",\"cveTags\":[],\"descriptions\":[{\"lang\":\"en\",\"value\":\"In the Linux kernel, the following vulnerability has been resolved:\\n\\ntipc: serialize udp bearer replicast list updates\\n\\ntipc_udp_rcast_add() and cleanup_bearer() both update ub-\u003ercast.list with\\nlist_add_rcu() / list_del_rcu(), but nothing serializes them. The add runs\\nfrom the encap receive softirq (via tipc_udp_rcast_disc()) without\\nrtnl_lock(), so it can race the cleanup delete and corrupt the list:\\n\\n  list_del corruption. prev-\u003enext should be ffff8880298d7ab8,\\n    but was ffff88802449ad38. (prev=ffff888027e3ec98)\\n  kernel BUG at lib/list_debug.c:62!\\n  RIP: __list_del_entry_valid_or_report+0x17a/0x200\\n  Workqueue: events cleanup_bearer\\n  Call Trace:\\n   cleanup_bearer (net/tipc/udp_media.c:811)\\n   process_one_work (kernel/workqueue.c:3302)\\n   worker_thread (kernel/workqueue.c:3466)\\n\\nThe bearer can be enabled from an unprivileged user namespace, as the\\nTIPCv2 generic-netlink ops carry no GENL_ADMIN_PERM.\\n\\nAdd a spinlock to struct udp_bearer and take it around the list_add_rcu()\\nin tipc_udp_rcast_add() and the list_del_rcu() loop in cleanup_bearer() so\\nthe two writers can no longer corrupt the list.\\n\\nReject a duplicate peer under the same lock before allocating, and remove\\ntipc_udp_is_known_peer(). The old lockless pre-check in\\ntipc_udp_rcast_disc() was racy: two softirqs discovering the same peer\\ncould both find it absent and add it twice.\\n\\ncleanup_bearer() runs from a workqueue after tipc_udp_disable() clears the\\nbearer\u0027s up bit, so an encap softirq can still reach tipc_udp_rcast_add()\\nand add a peer after cleanup_bearer() has already emptied the list, leaking\\nthat entry when the bearer is freed. Mark the bearer disabled under\\nrcast_lock once the list is emptied and refuse further additions.\"}],\"affected\":[{\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"affectedData\":[{\"vendor\":\"Linux\",\"product\":\"Linux\",\"defaultStatus\":\"unaffected\",\"programFiles\":[\"net/tipc/udp_media.c\"],\"repo\":\"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\"versions\":[{\"version\":\"ef20cd4dd1633987bcf46ac34ace2c8af212361f\",\"lessThan\":\"d70c81001df9320d3445e664428a1d408b5ba896\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"ef20cd4dd1633987bcf46ac34ace2c8af212361f\",\"lessThan\":\"350e592ff4e30e48ffb55e142d11a73e63f4869c\",\"versionType\":\"git\",\"status\":\"affected\"}]},{\"vendor\":\"Linux\",\"product\":\"Linux\",\"defaultStatus\":\"affected\",\"programFiles\":[\"net/tipc/udp_media.c\"],\"repo\":\"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\"versions\":[{\"version\":\"4.9\",\"status\":\"affected\"},{\"version\":\"0\",\"lessThan\":\"4.9\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"7.1.6\",\"lessThanOrEqual\":\"7.1.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"7.2\",\"lessThanOrEqual\":\"*\",\"versionType\":\"original_commit_for_fix\",\"status\":\"unaffected\"}]}]}],\"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/350e592ff4e30e48ffb55e142d11a73e63f4869c\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/d70c81001df9320d3445e664428a1d408b5ba896\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"}]}}",
    "redhat_vex": {
      "aggregate_severity": "Moderate",
      "current_release_date": "2026-08-13T23:27:48+00:00",
      "cve": "CVE-2026-68323",
      "id": "CVE-2026-68323",
      "initial_release_date": "2026-08-10T00:00:00+00:00",
      "product_status:known_affected": "234",
      "product_status:known_not_affected": "42",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: tipc: serialize udp bearer replicast list updates",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-68323.json",
      "version": "3"
    },
    "suse_vex": {
      "aggregate_severity": "moderate",
      "current_release_date": "2026-08-11T23:47:54Z",
      "cve": "CVE-2026-68323",
      "id": "CVE-2026-68323",
      "initial_release_date": "2026-08-11T23:47:54Z",
      "product_status:known_affected": "290",
      "product_status:known_not_affected": "6",
      "source": "SUSE CSAF VEX",
      "status": "interim",
      "title": "SUSE CVE CVE-2026-68323",
      "url": "https://ftp.suse.com/pub/projects/security/csaf-vex/cve-2026-68323.json",
      "version": "2"
    }
  }
}



Log in or create an account to share your comment.




Tags
Taxonomy of the tags.





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.


Detection rules are retrieved from Rulezet.