CVE-2026-98360 (GCVE-0-2026-98360)

Vulnerability from cvelistv5 – Published: 2026-10-06 08:46 – Updated: 2026-10-07 06:50
VLAI
Title
RDMA/rxe: insert mcg into mcg_tree only after rxe_mcast_add() succeeds
Summary
In the Linux kernel, the following vulnerability has been resolved: RDMA/rxe: insert mcg into mcg_tree only after rxe_mcast_add() succeeds rxe_get_mcg() publishes a newly allocated multicast group in rxe->mcg_tree before programming the backing Ethernet multicast address with rxe_mcast_add(), which runs outside mcg_lock. A local userspace RDMA client reaches this path with ATTACH_MCAST on a UD QP; if rxe_mcast_add() then returns an error (for example -ENODEV when the backing netdev has been removed, or a propagated dev_mc_add() error), the unwind frees the published group without removing it from the tree. A later lookup of the same MGID dereferences the freed struct rxe_mcg from __rxe_lookup_mcg(). Fix this by keeping the new mcg private until rxe_mcast_add() succeeds. Split the tree publication into __rxe_publish_mcg(), call rxe_mcast_add() before taking the tree reference, and free the still-private mcg on failure. Because the group is never visible in mcg_tree until the multicast address is programmed, no concurrent caller can look it up or attach a QP to a group that is about to be torn down, so the error path needs no conditional unwind. If another caller publishes the same MGID while the address is being programmed, the post-add re-check under mcg_lock finds the winner; this caller then drops its private object and balances its own rxe_mcast_add() with rxe_mcast_del() before returning the winner. Reproduced by forcing the rxe_mcast_add() error return under KASAN: without the change the next attach to the same MGID reports a slab-use-after-free in __rxe_lookup_mcg(); with it the forced failure returns cleanly. A no-injection attach/detach regression, including a two-QP shared join/leave and re-attach, stays KASAN- and leak-clean.
Severity
7 (High)
CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
Assigner
Linux CNA under the mitre root
CNA scorecard D 54/100 over 6633 records in the last 180 days details
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: a926a903b7dc39a8a949150258c09290998dd812 , < ddb43ac0926d4a931bc9b7744b93627f627457e5 (git)
Affected: a926a903b7dc39a8a949150258c09290998dd812 , < c79a789aa15180a1543b5db49c343d12e3ec214d (git)
Affected: a926a903b7dc39a8a949150258c09290998dd812 , < faae1fb4ccf8205806a8802c008798dabeb0205b (git)
Affected: a926a903b7dc39a8a949150258c09290998dd812 , < 02c0a2fa69c16248a7432af8a6d64ab2a73a5283 (git)
Affected: a926a903b7dc39a8a949150258c09290998dd812 , < d4fc4e37f8a143b0fe83b42c8fb48cf542154fee (git)
Affected: a926a903b7dc39a8a949150258c09290998dd812 , < 1caceeb2d74bbe88223aea55eb8626b4c5f076fd (git)
guessed Create a notification for this product.
Linux Linux Affected: 5.18
Unaffected: 0 , < 5.18 (semver)
Unaffected: 6.1.189 , ≤ 6.1.* (semver)
Unaffected: 6.6.158 , ≤ 6.6.* (semver)
Unaffected: 6.12.112 , ≤ 6.12.* (semver)
Unaffected: 6.18.54 , ≤ 6.18.* (semver)
Unaffected: 7.2.8 , ≤ 7.2.* (semver)
Unaffected: 7.3-rc4 , ≤ * (original_commit_for_fix)
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{
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          "product": "Linux",
          "programFiles": [
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      "descriptions": [
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          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nRDMA/rxe: insert mcg into mcg_tree only after rxe_mcast_add() succeeds\n\nrxe_get_mcg() publishes a newly allocated multicast group in\nrxe-\u003emcg_tree before programming the backing Ethernet multicast address\nwith rxe_mcast_add(), which runs outside mcg_lock. A local userspace\nRDMA client reaches this path with ATTACH_MCAST on a UD QP; if\nrxe_mcast_add() then returns an error (for example -ENODEV when the\nbacking netdev has been removed, or a propagated dev_mc_add() error),\nthe unwind frees the published group without removing it from the tree.\nA later lookup of the same MGID dereferences the freed struct rxe_mcg\nfrom __rxe_lookup_mcg().\n\nFix this by keeping the new mcg private until rxe_mcast_add() succeeds.\nSplit the tree publication into __rxe_publish_mcg(), call rxe_mcast_add()\nbefore taking the tree reference, and free the still-private mcg on\nfailure. Because the group is never visible in mcg_tree until the\nmulticast address is programmed, no concurrent caller can look it up or\nattach a QP to a group that is about to be torn down, so the error path\nneeds no conditional unwind. If another caller publishes the same MGID\nwhile the address is being programmed, the post-add re-check under\nmcg_lock finds the winner; this caller then drops its private object and\nbalances its own rxe_mcast_add() with rxe_mcast_del() before returning\nthe winner.\n\nReproduced by forcing the rxe_mcast_add() error return under KASAN:\nwithout the change the next attach to the same MGID reports a\nslab-use-after-free in __rxe_lookup_mcg(); with it the forced failure\nreturns cleanly. A no-injection attach/detach regression, including a\ntwo-QP shared join/leave and re-attach, stays KASAN- and leak-clean."
        }
      ],
      "metrics": [
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            "baseSeverity": "HIGH",
            "vectorString": "CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H",
            "version": "3.1"
          },
          "scenarios": [
            {
              "lang": "en",
              "value": "AV:L - The faulty publish-then-free sequence is in rxe_get_mcg(), reached from the uverbs ATTACH_MCAST command (ib_uverbs_attach_mcast -\u003e ib_attach_mcast -\u003e rxe_attach_mcast) on a local UD QP. A remote RoCEv2 multicast packet (rxe_rcv_mcast_pkt -\u003e rxe_lookup_mcg) can only hit the stale node after a local caller has already caused the failure.\nAC:H - The dangling mcg is only left behind when rxe_mcast_add() fails after the group is published. That needs ib_device_get_netdev() to return NULL while the rxe netdev is being unregistered (an admin or hardware event), or a GFP_ATOMIC failure in __hw_addr_create(). An unprivileged user cannot produce either on demand.\nPR:L - ib_uverbs_attach_mcast() and rxe_attach_mcast() have no capability check, so any user who can open the rxe uverbs device and create a UD QP can drive rxe_get_mcg(). Creating the rxe link itself (RDMA_NL_ADMIN_PERM, checked with netlink_capable against the init namespace) is admin setup the attacker does not perform.\nUI:N - The attacker issues ATTACH_MCAST for the failing MGID and then the follow-up attach/detach/lookup themselves; no other user has to act.\nS:U - The freed rxe_mcg is kernel heap memory in the same kernel security authority; there is no VM, IOMMU or sandbox boundary crossed.\nC:H - The freed struct rxe_mcg stays linked in rxe-\u003emcg_tree. __rxe_lookup_mcg() walks its rb_node and mgid, and later code follows its qp_list, so reallocating that slab slot with attacker-chosen data gives a heap read primitive.\nI:H - After the free, __rxe_lookup_mcg() does kref_get() on the stale object, and rxe_attach_mcg() list_add()s an mca into its qp_list and updates qp_num. These are writes into reallocated memory, and the rb-tree insert/erase relinks through the freed node.\nA:H - The next ATTACH_MCAST, detach, or received multicast lookup for that MGID dereferences the freed rxe_mcg (KASAN slab-use-after-free in __rxe_lookup_mcg()), corrupting the rb-tree and crashing the kernel."
            }
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        "shortName": "Linux"
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          "url": "https://git.kernel.org/stable/c/c79a789aa15180a1543b5db49c343d12e3ec214d"
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        {
          "url": "https://git.kernel.org/stable/c/1caceeb2d74bbe88223aea55eb8626b4c5f076fd"
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      "title": "RDMA/rxe: insert mcg into mcg_tree only after rxe_mcast_add() succeeds",
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    "assignerShortName": "Linux",
    "cveId": "CVE-2026-98360",
    "datePublished": "2026-10-06T08:46:46.743Z",
    "dateReserved": "2026-09-25T10:25:14.344Z",
    "dateUpdated": "2026-10-07T06:50:14.996Z",
    "state": "PUBLISHED"
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        "descriptions": [
          {
            "lang": "en",
            "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nRDMA/rxe: insert mcg into mcg_tree only after rxe_mcast_add() succeeds\n\nrxe_get_mcg() publishes a newly allocated multicast group in\nrxe-\u003emcg_tree before programming the backing Ethernet multicast address\nwith rxe_mcast_add(), which runs outside mcg_lock. A local userspace\nRDMA client reaches this path with ATTACH_MCAST on a UD QP; if\nrxe_mcast_add() then returns an error (for example -ENODEV when the\nbacking netdev has been removed, or a propagated dev_mc_add() error),\nthe unwind frees the published group without removing it from the tree.\nA later lookup of the same MGID dereferences the freed struct rxe_mcg\nfrom __rxe_lookup_mcg().\n\nFix this by keeping the new mcg private until rxe_mcast_add() succeeds.\nSplit the tree publication into __rxe_publish_mcg(), call rxe_mcast_add()\nbefore taking the tree reference, and free the still-private mcg on\nfailure. Because the group is never visible in mcg_tree until the\nmulticast address is programmed, no concurrent caller can look it up or\nattach a QP to a group that is about to be torn down, so the error path\nneeds no conditional unwind. If another caller publishes the same MGID\nwhile the address is being programmed, the post-add re-check under\nmcg_lock finds the winner; this caller then drops its private object and\nbalances its own rxe_mcast_add() with rxe_mcast_del() before returning\nthe winner.\n\nReproduced by forcing the rxe_mcast_add() error return under KASAN:\nwithout the change the next attach to the same MGID reports a\nslab-use-after-free in __rxe_lookup_mcg(); with it the forced failure\nreturns cleanly. A no-injection attach/detach regression, including a\ntwo-QP shared join/leave and re-attach, stays KASAN- and leak-clean."
          }
        ],
        "id": "CVE-2026-98360",
        "lastModified": "2026-10-07T07:17:10.447",
        "metrics": {
          "cvssMetricV31": [
            {
              "cvssData": {
                "attackComplexity": "HIGH",
                "attackVector": "LOCAL",
                "availabilityImpact": "HIGH",
                "baseScore": 7.0,
                "baseSeverity": "HIGH",
                "confidentialityImpact": "HIGH",
                "integrityImpact": "HIGH",
                "privilegesRequired": "LOW",
                "scope": "UNCHANGED",
                "userInteraction": "NONE",
                "vectorString": "CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H",
                "version": "3.1"
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              "impactScore": 5.9,
              "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
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        "published": "2026-10-06T09:18:29.803",
        "references": [
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            "url": "https://git.kernel.org/stable/c/02c0a2fa69c16248a7432af8a6d64ab2a73a5283"
          },
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          },
          {
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            "url": "https://git.kernel.org/stable/c/ddb43ac0926d4a931bc9b7744b93627f627457e5"
          },
          {
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "url": "https://git.kernel.org/stable/c/faae1fb4ccf8205806a8802c008798dabeb0205b"
          }
        ],
        "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "vulnStatus": "Received"
      }
    },
    "redhat_vex": {
      "aggregate_severity": "Moderate",
      "current_release_date": "2026-10-07T08:31:54+00:00",
      "cve": "CVE-2026-98360",
      "id": "CVE-2026-98360",
      "initial_release_date": "2026-10-06T00:00:00+00:00",
      "product_status:known_affected": "155",
      "product_status:known_not_affected": "122",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: RDMA/rxe: insert mcg into mcg_tree only after rxe_mcast_add() succeeds",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-98360.json",
      "version": "3"
    }
  }
}



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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.
  • 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.



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.