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CVE-2025-21759 (GCVE-0-2025-21759)

Vulnerability from cvelistv5 – Published: 2025-02-27 02:18 – Updated: 2026-08-05 11:54
VLAI
Title
ipv6: mcast: extend RCU protection in igmp6_send()
Summary
In the Linux kernel, the following vulnerability has been resolved: ipv6: mcast: extend RCU protection in igmp6_send() igmp6_send() can be called without RTNL or RCU being held. Extend RCU protection so that we can safely fetch the net pointer and avoid a potential UAF. Note that we no longer can use sock_alloc_send_skb() because ipv6.igmp_sk uses GFP_KERNEL allocations which can sleep. Instead use alloc_skb() and charge the net->ipv6.igmp_sk socket under RCU protection.
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: b8ad0cbc58f703972e9e37c4e2a8081dd7e6a551 , < 81b25a07ebf53f9ef4ca8f3d96a8ddb94561dd5a (git)
Affected: b8ad0cbc58f703972e9e37c4e2a8081dd7e6a551 , < 0bf8e2f3768629d437a32cb824149e6e98254381 (git)
Affected: b8ad0cbc58f703972e9e37c4e2a8081dd7e6a551 , < 8e92d6a413feaf968a33f0b439ecf27404407458 (git)
Affected: b8ad0cbc58f703972e9e37c4e2a8081dd7e6a551 , < 087c1faa594fa07a66933d750c0b2610aa1a2946 (git)
guessed Create a notification for this product.
Linux Linux Affected: 2.6.26
Unaffected: 0 , < 2.6.26 (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.
Show details on NVD website
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                        "Automatable": "no"
                      },
                      {
                        "Technical Impact": "total"
                      }
                    ],
                    "role": "CISA Coordinator",
                    "timestamp": "2025-02-27T17:57:46.460072Z",
                    "version": "2.0.3"
                  },
                  "type": "ssvc"
                }
              }
            ],
            "problemTypes": [
              {
                "descriptions": [
                  {
                    "cweId": "CWE-416",
                    "description": "CWE-416 Use After Free",
                    "lang": "en",
                    "type": "CWE"
                  }
                ]
              }
            ],
            "providerMetadata": {
              "dateUpdated": "2025-02-27T17:57:47.940Z",
              "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
              "shortName": "CISA-ADP"
            },
            "title": "CISA ADP Vulnrichment"
          }
        ],
        "cna": {
          "affected": [
            {
              "defaultStatus": "unaffected",
              "product": "Linux",
              "programFiles": [
                "net/ipv6/mcast.c"
              ],
              "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
              "vendor": "Linux",
              "versions": [
                {
                  "lessThan": "81b25a07ebf53f9ef4ca8f3d96a8ddb94561dd5a",
                  "status": "affected",
                  "version": "b8ad0cbc58f703972e9e37c4e2a8081dd7e6a551",
                  "versionType": "git"
                },
                {
                  "lessThan": "0bf8e2f3768629d437a32cb824149e6e98254381",
                  "status": "affected",
                  "version": "b8ad0cbc58f703972e9e37c4e2a8081dd7e6a551",
                  "versionType": "git"
                },
                {
                  "lessThan": "8e92d6a413feaf968a33f0b439ecf27404407458",
                  "status": "affected",
                  "version": "b8ad0cbc58f703972e9e37c4e2a8081dd7e6a551",
                  "versionType": "git"
                },
                {
                  "lessThan": "087c1faa594fa07a66933d750c0b2610aa1a2946",
                  "status": "affected",
                  "version": "b8ad0cbc58f703972e9e37c4e2a8081dd7e6a551",
                  "versionType": "git"
                }
              ]
            },
            {
              "defaultStatus": "affected",
              "product": "Linux",
              "programFiles": [
                "net/ipv6/mcast.c"
              ],
              "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
              "vendor": "Linux",
              "versions": [
                {
                  "status": "affected",
                  "version": "2.6.26"
                },
                {
                  "lessThan": "2.6.26",
                  "status": "unaffected",
                  "version": "0",
                  "versionType": "semver"
                },
                {
                  "lessThanOrEqual": "6.6.*",
                  "status": "unaffected",
                  "version": "6.6.79",
                  "versionType": "semver"
                },
                {
                  "lessThanOrEqual": "6.12.*",
                  "status": "unaffected",
                  "version": "6.12.16",
                  "versionType": "semver"
                },
                {
                  "lessThanOrEqual": "6.13.*",
                  "status": "unaffected",
                  "version": "6.13.4",
                  "versionType": "semver"
                },
                {
                  "lessThanOrEqual": "*",
                  "status": "unaffected",
                  "version": "6.14",
                  "versionType": "original_commit_for_fix"
                }
              ]
            }
          ],
          "cpeApplicability": [
            {
              "nodes": [
                {
                  "cpeMatch": [
                    {
                      "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                      "versionEndExcluding": "6.6.79",
                      "versionStartIncluding": "2.6.26",
                      "vulnerable": true
                    },
                    {
                      "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                      "versionEndExcluding": "6.12.16",
                      "versionStartIncluding": "2.6.26",
                      "vulnerable": true
                    },
                    {
                      "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                      "versionEndExcluding": "6.13.4",
                      "versionStartIncluding": "2.6.26",
                      "vulnerable": true
                    },
                    {
                      "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                      "versionEndExcluding": "6.14",
                      "versionStartIncluding": "2.6.26",
                      "vulnerable": true
                    }
                  ],
                  "negate": false,
                  "operator": "OR"
                }
              ]
            }
          ],
          "descriptions": [
            {
              "lang": "en",
              "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nipv6: mcast: extend RCU protection in igmp6_send()\n\nigmp6_send() can be called without RTNL or RCU being held.\n\nExtend RCU protection so that we can safely fetch the net pointer\nand avoid a potential UAF.\n\nNote that we no longer can use sock_alloc_send_skb() because\nipv6.igmp_sk uses GFP_KERNEL allocations which can sleep.\n\nInstead use alloc_skb() and charge the net-\u003eipv6.igmp_sk\nsocket under RCU protection."
            }
          ],
          "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 - Although igmp6_send() can be scheduled by adjacent MLD Query packets, the freeing side of the race requires network-namespace dismantle or a netdev netns move, which is driven by local syscalls (unshare/setns, RTM_NEWLINK with IFLA_NET_NS_FD, process exit). A local unprivileged user controls both sides of the race entirely, making local access the reliable exploitation vector.\nAC:L - The attacker drives both halves: they schedule igmp6_send() at will (multicast join/leave, link up/down, or timed MLD reports) and trigger the free by destroying their own netns or moving the device out of it, and can retry the race indefinitely while heap-grooming the freed struct net/struct sock.\nPR:L - Only an unprivileged local account is needed \u2014 the CAP_NET_ADMIN checks on the netns-move path are ns_capable() against the target netns user_ns, which is satisfied inside a user namespace created with unshare -Urn, and IPv6 multicast joins require no privilege at all.\nUI:N - The entire sequence \u2014 namespace setup, multicast group joins, and namespace teardown \u2014 is performed by the attacker\u0027s own processes with no action from any other user.\nS:U - The corrupted objects (struct net, struct sock) and the resulting code execution are all within the kernel\u0027s own security authority; no hypervisor, IOMMU, or other security boundary is crossed.\nC:H - The use-after-free reads sk-\u003esk_sndbuf, sk-\u003esk_allocation, sk-\u003esk_socket, net-\u003emib pointers and net-\u003enf.hooks_ipv6[] from freed-and-reallocated memory, giving an attacker who sprays the freed slab a controllable pointer-dereference primitive that can be turned into arbitrary kernel memory disclosure.\nI:H - skb_set_owner_w() performs refcount_add() into the freed socket and NF_HOOK() calls a function pointer fetched from the freed struct net\u0027s netfilter hook array, yielding both a write primitive and control-flow hijack suitable for full privilege escalation.\nA:H - Dereferencing a freed struct net and its igmp_sk reliably produces a kernel oops/panic (slab-use-after-free, invalid pointer dereference in the netfilter or socket accounting path), and the race can be repeated to crash the machine."
                }
              ]
            }
          ],
          "providerMetadata": {
            "dateUpdated": "2026-08-05T11:54:12.048Z",
            "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "shortName": "Linux"
          },
          "references": [
            {
              "url": "https://git.kernel.org/stable/c/81b25a07ebf53f9ef4ca8f3d96a8ddb94561dd5a"
            },
            {
              "url": "https://git.kernel.org/stable/c/0bf8e2f3768629d437a32cb824149e6e98254381"
            },
            {
              "url": "https://git.kernel.org/stable/c/8e92d6a413feaf968a33f0b439ecf27404407458"
            },
            {
              "url": "https://git.kernel.org/stable/c/087c1faa594fa07a66933d750c0b2610aa1a2946"
            }
          ],
          "title": "ipv6: mcast: extend RCU protection in igmp6_send()",
          "x_generator": {
            "engine": "bippy-1.2.0"
          }
        }
      },
      "cveMetadata": {
        "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "assignerShortName": "Linux",
        "cveId": "CVE-2025-21759",
        "datePublished": "2025-02-27T02:18:12.994Z",
        "dateReserved": "2024-12-29T08:45:45.761Z",
        "dateUpdated": "2026-08-05T11:54:12.048Z",
        "state": "PUBLISHED"
      },
      "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

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.


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.