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CVE-2026-80994 (GCVE-0-2026-80994)

Vulnerability from cvelistv5 – Published: 2026-09-11 19:42 – Updated: 2026-09-14 11:59
VLAI
Title
net: openvswitch: fix flow mask use-after-free on flow deletion
Summary
In the Linux kernel, the following vulnerability has been resolved: net: openvswitch: fix flow mask use-after-free on flow deletion The commit in the Fixes tag below made so flow->mask free is scheduled via RCU right after it is removed from the flow table. The pointer stays in the flow structure and it can be accessible while in the same RCU critical section. This is done to avoid requiring ovs_mutex for the ovs_flow_free(). However, while removing the flow during processing of CMD_DEL, we do not take RCU read lock before the removal, and ovs_flow_cmd_fill_info() uses the flow->mask pointer afterwards. The RCU read lock is taken, but it's already late at that point. The comment on that line acknowledges that the lock is cosmetic and doesn't serve a real purpose. This leads to use-after-free if the RCU grace period passes between removal and the filling. It is a short race window, but it is there and can lead to a real crash in case memory allocation for the info takes a bit longer: BUG: KASAN: slab-use-after-free in __ovs_nla_put_key net/openvswitch/flow_netlink.c:1996 BUG: KASAN: slab-use-after-free in ovs_nla_put_key+0x2463/0x2e30 net/openvswitch/flow_netlink.c:2250 Read of size 4 at addr ffff88801ee89970 by task ovs_flow_del_ec/9487 Call Trace: <TASK> __ovs_nla_put_key net/openvswitch/flow_netlink.c:1996 ovs_nla_put_key+0x2463/0x2e30 net/openvswitch/flow_netlink.c:2250 ovs_flow_cmd_fill_info+0x420/0x9c0 net/openvswitch/datapath.c:930 ovs_flow_cmd_del+0x53a/0x970 net/openvswitch/datapath.c:1467 ... netlink_rcv_skb+0x156/0x420 net/netlink/af_netlink.c:2556 </TASK> Allocated by task 9487: mask_alloc net/openvswitch/flow_table.c:967 flow_mask_insert net/openvswitch/flow_table.c:1012 ovs_flow_tbl_insert+0xea2/0x1a90 net/openvswitch/flow_table.c:1084 ovs_flow_cmd_new+0x7e3/0xd90 net/openvswitch/datapath.c:1086 ... netlink_rcv_skb+0x156/0x420 net/netlink/af_netlink.c:2556 Freed by task 9485: rcu_free_sheaf+0x1e/0x100 mm/slub.c:5978 rcu_do_batch kernel/rcu/tree.c:2645 rcu_core+0x59c/0x10c0 kernel/rcu/tree.c:2897 handle_softirqs+0x1e4/0x9a0 kernel/softirq.c:622 ... instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1062 ovs_flow_tbl_remove() must be called after the ovs_flow_cmd_fill_info() to avoid this race. This also helps with cleaning up the forced cast and the cosmetic RCU read lock. Before the commit in the Fixes tag the order did not matter as long as the flow object itself was not freed. A wider RCU critical section could be another option, but we have a GFP_KERNEL allocation in the way. Reported by Trend Micro's Zero Day Initiative as ZDI-CAN-32042.
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: 56c19868e115fcf8d62d843e1b9616bb9837d0db , < ea5f7b45b582665541ddfb77dce98611354af4ab (git)
Affected: 56c19868e115fcf8d62d843e1b9616bb9837d0db , < 18ce1a8b7499c016d4a893d9b1db80608f73745d (git)
Affected: 56c19868e115fcf8d62d843e1b9616bb9837d0db , < c15ef9a5bf594f93a31de2ec2ec394e2a903519a (git)
Affected: 56c19868e115fcf8d62d843e1b9616bb9837d0db , < 64051fe200c7c759af71634bd2123552eaabb69a (git)
Affected: 56c19868e115fcf8d62d843e1b9616bb9837d0db , < 0ba5cbc2f049af94ec94ff6f64958545efc5eaa2 (git)
Affected: 56c19868e115fcf8d62d843e1b9616bb9837d0db , < ac73e3af571da06c1d1cfe3f0f00dc978b851700 (git)
Affected: 56c19868e115fcf8d62d843e1b9616bb9837d0db , < 7f072b84afd05a77963eb1872f7174e280661dce (git)
Affected: 56c19868e115fcf8d62d843e1b9616bb9837d0db , < 4e30317ff67a2eb12b4d890d39f72fd7e7117d48 (git)
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Linux Linux Affected: 3.16
Unaffected: 0 , < 3.16 (semver)
Unaffected: 5.10.270 , ≤ 5.10.* (semver)
Unaffected: 5.15.221 , ≤ 5.15.* (semver)
Unaffected: 6.1.188 , ≤ 6.1.* (semver)
Unaffected: 6.6.157 , ≤ 6.6.* (semver)
Unaffected: 6.12.109 , ≤ 6.12.* (semver)
Unaffected: 6.18.50 , ≤ 6.18.* (semver)
Unaffected: 7.2.4 , ≤ 7.2.* (semver)
Unaffected: 7.3-rc1 , ≤ * (original_commit_for_fix)
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      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet: openvswitch: fix flow mask use-after-free on flow deletion\n\nThe commit in the Fixes tag below made so flow-\u003emask free is scheduled\nvia RCU right after it is removed from the flow table.  The pointer\nstays in the flow structure and it can be accessible while in the same\nRCU critical section.  This is done to avoid requiring ovs_mutex for\nthe ovs_flow_free().\n\nHowever, while removing the flow during processing of CMD_DEL, we do\nnot take RCU read lock before the removal, and ovs_flow_cmd_fill_info()\nuses the flow-\u003emask pointer afterwards.  The RCU read lock is taken,\nbut it\u0027s already late at that point.  The comment on that line\nacknowledges that the lock is cosmetic and doesn\u0027t serve a real purpose.\n\nThis leads to use-after-free if the RCU grace period passes between\nremoval and the filling.  It is a short race window, but it is there\nand can lead to a real crash in case memory allocation for the info\ntakes a bit longer:\n\n BUG: KASAN: slab-use-after-free in __ovs_nla_put_key\n             net/openvswitch/flow_netlink.c:1996\n BUG: KASAN: slab-use-after-free in ovs_nla_put_key+0x2463/0x2e30\n             net/openvswitch/flow_netlink.c:2250\n Read of size 4 at addr ffff88801ee89970 by task ovs_flow_del_ec/9487\n\n Call Trace:\n  \u003cTASK\u003e\n  __ovs_nla_put_key net/openvswitch/flow_netlink.c:1996\n  ovs_nla_put_key+0x2463/0x2e30 net/openvswitch/flow_netlink.c:2250\n  ovs_flow_cmd_fill_info+0x420/0x9c0 net/openvswitch/datapath.c:930\n  ovs_flow_cmd_del+0x53a/0x970 net/openvswitch/datapath.c:1467\n  ...\n  netlink_rcv_skb+0x156/0x420 net/netlink/af_netlink.c:2556\n  \u003c/TASK\u003e\n\n Allocated by task 9487:\n  mask_alloc net/openvswitch/flow_table.c:967\n  flow_mask_insert net/openvswitch/flow_table.c:1012\n  ovs_flow_tbl_insert+0xea2/0x1a90 net/openvswitch/flow_table.c:1084\n  ovs_flow_cmd_new+0x7e3/0xd90 net/openvswitch/datapath.c:1086\n  ...\n  netlink_rcv_skb+0x156/0x420 net/netlink/af_netlink.c:2556\n\n Freed by task 9485:\n  rcu_free_sheaf+0x1e/0x100 mm/slub.c:5978\n  rcu_do_batch kernel/rcu/tree.c:2645\n  rcu_core+0x59c/0x10c0 kernel/rcu/tree.c:2897\n  handle_softirqs+0x1e4/0x9a0 kernel/softirq.c:622\n  ...\n  instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1062\n\novs_flow_tbl_remove() must be called after the ovs_flow_cmd_fill_info()\nto avoid this race.  This also helps with cleaning up the forced cast\nand the cosmetic RCU read lock.  Before the commit in the Fixes tag the\norder did not matter as long as the flow object itself was not freed.\n\nA wider RCU critical section could be another option, but we have a\nGFP_KERNEL allocation in the way.\n\nReported by Trend Micro\u0027s Zero Day Initiative as ZDI-CAN-32042."
        }
      ],
      "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 - The UAF is reached only through OVS_FLOW_CMD_DEL on the ovs_flow Generic Netlink family via a local sendmsg() on an AF_NETLINK socket; packet receive and remote protocols cannot delete flows or call ovs_flow_cmd_del().\nAC:L - The attacker owns unique-mask flow insert and CMD_DEL with NLM_F_ECHO; after ovs_unlock(), GFP_KERNEL genlmsg_new() can sleep under attacker-induced memory pressure until kfree_rcu() of sw_flow_mask completes, so the race is attacker-controlled and repeatable.\nPR:L - OVS_FLOW_CMD_DEL/NEW and OVS_DP_CMD_NEW use GENL_UNS_ADMIN_PERM with netnsok, so only CAP_NET_ADMIN in the socket user namespace is required; an unprivileged user obtains that via unshare -Urn, and MODULE_ALIAS_GENL_FAMILY autoloads openvswitch.ko.\nUI:N - The attacker creates the datapath, installs a unique-mask flow, and deletes it with NLM_F_ECHO from their own process; no victim action is required.\nS:U - The slab use-after-free of sw_flow_mask stays in kernel heap on the same host and does not cross a VM, IOMMU, or hypervisor boundary.\nC:H - ovs_nla_put_mask() reads the freed flow-\u003emask-\u003ekey and copies it into the CMD_DEL netlink reply delivered to the attacker, so a reused or heap-sprayed slab object becomes an arbitrary kernel-memory disclosure primitive.\nI:H - This is a slab use-after-free of sw_flow_mask; after kfree_rcu() the attacker can reclaim the object so fill-info interprets attacker-controlled bytes as a flow mask, enabling heap spraying and write/control-flow primitives.\nA:H - KASAN reports a slab-use-after-free in __ovs_nla_put_key during ovs_flow_cmd_del, and dereference of the freed mask can oops or panic the kernel; the attacker can repeat CMD_DEL to deny availability."
            }
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        }
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      "providerMetadata": {
        "dateUpdated": "2026-09-14T11:59:34.227Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/ea5f7b45b582665541ddfb77dce98611354af4ab"
        },
        {
          "url": "https://git.kernel.org/stable/c/18ce1a8b7499c016d4a893d9b1db80608f73745d"
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        },
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          "url": "https://git.kernel.org/stable/c/64051fe200c7c759af71634bd2123552eaabb69a"
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        }
      ],
      "title": "net: openvswitch: fix flow mask use-after-free on flow deletion",
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    "assignerShortName": "Linux",
    "cveId": "CVE-2026-80994",
    "datePublished": "2026-09-11T19:42:50.199Z",
    "dateReserved": "2026-08-26T14:34:25.812Z",
    "dateUpdated": "2026-09-14T11:59:34.227Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2",
  "vulnerability-lookup:meta": {
    "epss": {
      "cve": "CVE-2026-80994",
      "date": "2026-09-17",
      "epss": "0.00159",
      "percentile": "0.05508"
    },
    "microsoft_vex": {
      "current_release_date": "2026-09-14T14:54:41.000Z",
      "cve": "CVE-2026-80994",
      "id": "msrc_CVE-2026-80994",
      "initial_release_date": "2026-09-13T01:08:06.000Z",
      "product_status:known_affected": "1",
      "source": "Microsoft CSAF VEX",
      "status": "final",
      "title": "net: openvswitch: fix flow mask use-after-free on flow deletion",
      "url": "https://msrc.microsoft.com/csaf/vex/2026/msrc_cve-2026-80994.json",
      "version": "2"
    },
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                    "lessThanOrEqual": "6.18.*",
                    "status": "unaffected",
                    "version": "6.18.50",
                    "versionType": "semver"
                  },
                  {
                    "lessThanOrEqual": "7.2.*",
                    "status": "unaffected",
                    "version": "7.2.4",
                    "versionType": "semver"
                  },
                  {
                    "lessThanOrEqual": "*",
                    "status": "unaffected",
                    "version": "7.3-rc1",
                    "versionType": "original_commit_for_fix"
                  }
                ]
              }
            ],
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
          }
        ],
        "cveTags": [],
        "descriptions": [
          {
            "lang": "en",
            "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet: openvswitch: fix flow mask use-after-free on flow deletion\n\nThe commit in the Fixes tag below made so flow-\u003emask free is scheduled\nvia RCU right after it is removed from the flow table.  The pointer\nstays in the flow structure and it can be accessible while in the same\nRCU critical section.  This is done to avoid requiring ovs_mutex for\nthe ovs_flow_free().\n\nHowever, while removing the flow during processing of CMD_DEL, we do\nnot take RCU read lock before the removal, and ovs_flow_cmd_fill_info()\nuses the flow-\u003emask pointer afterwards.  The RCU read lock is taken,\nbut it\u0027s already late at that point.  The comment on that line\nacknowledges that the lock is cosmetic and doesn\u0027t serve a real purpose.\n\nThis leads to use-after-free if the RCU grace period passes between\nremoval and the filling.  It is a short race window, but it is there\nand can lead to a real crash in case memory allocation for the info\ntakes a bit longer:\n\n BUG: KASAN: slab-use-after-free in __ovs_nla_put_key\n             net/openvswitch/flow_netlink.c:1996\n BUG: KASAN: slab-use-after-free in ovs_nla_put_key+0x2463/0x2e30\n             net/openvswitch/flow_netlink.c:2250\n Read of size 4 at addr ffff88801ee89970 by task ovs_flow_del_ec/9487\n\n Call Trace:\n  \u003cTASK\u003e\n  __ovs_nla_put_key net/openvswitch/flow_netlink.c:1996\n  ovs_nla_put_key+0x2463/0x2e30 net/openvswitch/flow_netlink.c:2250\n  ovs_flow_cmd_fill_info+0x420/0x9c0 net/openvswitch/datapath.c:930\n  ovs_flow_cmd_del+0x53a/0x970 net/openvswitch/datapath.c:1467\n  ...\n  netlink_rcv_skb+0x156/0x420 net/netlink/af_netlink.c:2556\n  \u003c/TASK\u003e\n\n Allocated by task 9487:\n  mask_alloc net/openvswitch/flow_table.c:967\n  flow_mask_insert net/openvswitch/flow_table.c:1012\n  ovs_flow_tbl_insert+0xea2/0x1a90 net/openvswitch/flow_table.c:1084\n  ovs_flow_cmd_new+0x7e3/0xd90 net/openvswitch/datapath.c:1086\n  ...\n  netlink_rcv_skb+0x156/0x420 net/netlink/af_netlink.c:2556\n\n Freed by task 9485:\n  rcu_free_sheaf+0x1e/0x100 mm/slub.c:5978\n  rcu_do_batch kernel/rcu/tree.c:2645\n  rcu_core+0x59c/0x10c0 kernel/rcu/tree.c:2897\n  handle_softirqs+0x1e4/0x9a0 kernel/softirq.c:622\n  ...\n  instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1062\n\novs_flow_tbl_remove() must be called after the ovs_flow_cmd_fill_info()\nto avoid this race.  This also helps with cleaning up the forced cast\nand the cosmetic RCU read lock.  Before the commit in the Fixes tag the\norder did not matter as long as the flow object itself was not freed.\n\nA wider RCU critical section could be another option, but we have a\nGFP_KERNEL allocation in the way.\n\nReported by Trend Micro\u0027s Zero Day Initiative as ZDI-CAN-32042."
          }
        ],
        "id": "CVE-2026-80994",
        "lastModified": "2026-09-14T13:18:54.043",
        "metrics": {
          "cvssMetricV31": [
            {
              "cvssData": {
                "attackComplexity": "LOW",
                "attackVector": "LOCAL",
                "availabilityImpact": "HIGH",
                "baseScore": 7.8,
                "baseSeverity": "HIGH",
                "confidentialityImpact": "HIGH",
                "integrityImpact": "HIGH",
                "privilegesRequired": "LOW",
                "scope": "UNCHANGED",
                "userInteraction": "NONE",
                "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
                "version": "3.1"
              },
              "exploitabilityScore": 1.8,
              "impactScore": 5.9,
              "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
              "type": "Secondary"
            }
          ]
        },
        "published": "2026-09-11T20:19:06.357",
        "references": [
          {
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "url": "https://git.kernel.org/stable/c/0ba5cbc2f049af94ec94ff6f64958545efc5eaa2"
          },
          {
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "url": "https://git.kernel.org/stable/c/18ce1a8b7499c016d4a893d9b1db80608f73745d"
          },
          {
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "url": "https://git.kernel.org/stable/c/4e30317ff67a2eb12b4d890d39f72fd7e7117d48"
          },
          {
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "url": "https://git.kernel.org/stable/c/64051fe200c7c759af71634bd2123552eaabb69a"
          },
          {
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "url": "https://git.kernel.org/stable/c/7f072b84afd05a77963eb1872f7174e280661dce"
          },
          {
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "url": "https://git.kernel.org/stable/c/ac73e3af571da06c1d1cfe3f0f00dc978b851700"
          },
          {
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "url": "https://git.kernel.org/stable/c/c15ef9a5bf594f93a31de2ec2ec394e2a903519a"
          },
          {
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "url": "https://git.kernel.org/stable/c/ea5f7b45b582665541ddfb77dce98611354af4ab"
          }
        ],
        "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "vulnStatus": "Received"
      }
    },
    "redhat_vex": {
      "aggregate_severity": "Moderate",
      "current_release_date": "2026-09-14T20:16:10+00:00",
      "cve": "CVE-2026-80994",
      "id": "CVE-2026-80994",
      "initial_release_date": "2026-09-11T00:00:00+00:00",
      "product_status:known_affected": "276",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: net: openvswitch: fix flow mask use-after-free on flow deletion",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-80994.json",
      "version": "3"
    },
    "suse_vex": {
      "aggregate_severity": "moderate",
      "current_release_date": "2026-09-15T01:04:28Z",
      "cve": "CVE-2026-80994",
      "id": "CVE-2026-80994",
      "initial_release_date": "2026-09-15T01:04:28Z",
      "product_status:known_affected": "349",
      "product_status:known_not_affected": "4",
      "source": "SUSE CSAF VEX",
      "status": "interim",
      "title": "SUSE CVE CVE-2026-80994",
      "url": "https://ftp.suse.com/pub/projects/security/csaf-vex/cve-2026-80994.json",
      "version": "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.
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  • 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.


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