CVE-2026-63971 (GCVE-0-2026-63971)

Vulnerability from cvelistv5 – Published: 2026-07-19 14:55 – Updated: 2026-08-05 12:37
VLAI
Title
sctp: fix race between sctp_wait_for_connect and peeloff
Summary
In the Linux kernel, the following vulnerability has been resolved: sctp: fix race between sctp_wait_for_connect and peeloff sctp_wait_for_connect() drops and re-acquires the socket lock while waiting for the association to reach ESTABLISHED state. During this window, another thread can peeloff the association to a new socket via getsockopt(SCTP_SOCKOPT_PEELOFF), changing asoc->base.sk. After re-acquiring the old socket lock, sctp_wait_for_connect() returns success without noticing the migration — the caller then accesses the association under the wrong lock in sctp_datamsg_from_user(). Add the same sk != asoc->base.sk check that sctp_wait_for_sndbuf() already has, returning an error if the association was migrated while we slept.
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: 668c9beb9020d5834ee9e43c208190a07d2b1928 , < 0e0d5bc76fd4267a71334fcc8f1a5fbcf997845d (git)
Affected: 668c9beb9020d5834ee9e43c208190a07d2b1928 , < bcfeac79af740735ace44008b4a11b8e5add20f5 (git)
Affected: 668c9beb9020d5834ee9e43c208190a07d2b1928 , < 8e9b56051d24540cfbf39194618708c4a7633549 (git)
Affected: 668c9beb9020d5834ee9e43c208190a07d2b1928 , < 634a9af8a26a84d8b0d7b3b643204b344b42d9fb (git)
Affected: 668c9beb9020d5834ee9e43c208190a07d2b1928 , < 7d2038d4b80166f7bead8d07eba3b97405816c21 (git)
Affected: 668c9beb9020d5834ee9e43c208190a07d2b1928 , < 68667ee4c7dadf7f63167234e2a1af09b3f7874e (git)
Affected: 668c9beb9020d5834ee9e43c208190a07d2b1928 , < 6140cfa721451fa6e18e134e709703c2bf34d0fb (git)
Affected: 668c9beb9020d5834ee9e43c208190a07d2b1928 , < f14fe6395a8b3d961a61e138ad7b36ba3626dd4e (git)
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Linux Linux Affected: 4.16
Unaffected: 0 , < 4.16 (semver)
Unaffected: 5.10.259 , ≤ 5.10.* (semver)
Unaffected: 5.15.210 , ≤ 5.15.* (semver)
Unaffected: 6.1.176 , ≤ 6.1.* (semver)
Unaffected: 6.6.143 , ≤ 6.6.* (semver)
Unaffected: 6.12.93 , ≤ 6.12.* (semver)
Unaffected: 6.18.35 , ≤ 6.18.* (semver)
Unaffected: 7.0.12 , ≤ 7.0.* (semver)
Unaffected: 7.1 , ≤ * (original_commit_for_fix)
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          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nsctp: fix race between sctp_wait_for_connect and peeloff\n\nsctp_wait_for_connect() drops and re-acquires the socket lock while\nwaiting for the association to reach ESTABLISHED state. During this\nwindow, another thread can peeloff the association to a new socket via\ngetsockopt(SCTP_SOCKOPT_PEELOFF), changing asoc-\u003ebase.sk. After\nre-acquiring the old socket lock, sctp_wait_for_connect() returns\nsuccess without noticing the migration \u2014 the caller then accesses\nthe association under the wrong lock in sctp_datamsg_from_user().\n\nAdd the same sk != asoc-\u003ebase.sk check that sctp_wait_for_sndbuf()\nalready has, returning an error if the association was migrated while\nwe slept."
        }
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            "version": "3.1"
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              "value": "AV:L - Exploitation requires local syscalls on an SCTP socket (`sendmsg`/`sendto` to trigger `sctp_wait_for_connect`, and `getsockopt(SCTP_SOCKOPT_PEELOFF)` to peel off the association). A remote peer can only help complete the SCTP handshake; it cannot invoke peeloff or the racing send path.\nAC:L - The attacker controls both sides of the race by running concurrent threads on the same SCTP one-to-many socket, timing peeloff during the window where `sctp_wait_for_connect()` has released the socket lock. Required options (`SCTP_FRAGMENT_INTERLEAVE`, `SCTP_INTERLEAVING_SUPPORTED`, and `net.sctp.intl_enable`) are attacker-settable in a user/net namespace.\nPR:L - No real-root capability is required; an unprivileged user can create SCTP sockets and drive the full race from a user namespace (`unshare -Urn`), including enabling `net.sctp.intl_enable` and the interleaving socket options needed to reach the vulnerable `sctp_sendmsg_to_asoc()` path.\nUI:N - Exploitation is fully attacker-driven through coordinated local threads and does not require any action from a victim user or administrator beyond normal SCTP socket use.\nS:U - Impact is confined to kernel memory integrity/availability within the same security authority; successful exploitation would be local privilege escalation, not a cross-boundary escape such as VM or container breakout by itself.\nC:H - After peeloff migrates `asoc-\u003ebase.sk`, the caller continues in `sctp_datamsg_from_user()` while holding the wrong socket lock, creating unsynchronized concurrent access to association/stream state that can corrupt kernel heap metadata and be leveraged for arbitrary kernel memory disclosure.\nI:H - The post-race path builds and queues DATA/I-DATA chunks via `sctp_datamsg_from_user()` and `sctp_primitive_SEND()` without the correct socket lock, enabling concurrent modification of association output queues and stream structures that can be turned into arbitrary kernel writes or control-flow hijacking.\nA:H - Concurrent unsynchronized access to a live SCTP association after peeloff can cause kernel oops/panic or wedged associations, and the underlying race is a classic kernel concurrency defect with high availability impact even before full exploitation."
            }
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        "dateUpdated": "2026-08-05T12:37:42.789Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
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          "url": "https://git.kernel.org/stable/c/bcfeac79af740735ace44008b4a11b8e5add20f5"
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          "url": "https://git.kernel.org/stable/c/8e9b56051d24540cfbf39194618708c4a7633549"
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          "url": "https://git.kernel.org/stable/c/f14fe6395a8b3d961a61e138ad7b36ba3626dd4e"
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      "title": "sctp: fix race between sctp_wait_for_connect and peeloff",
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    "cveId": "CVE-2026-63971",
    "datePublished": "2026-07-19T14:55:57.792Z",
    "dateReserved": "2026-07-19T07:54:57.024Z",
    "dateUpdated": "2026-08-05T12:37:42.789Z",
    "state": "PUBLISHED"
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            "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nsctp: fix race between sctp_wait_for_connect and peeloff\n\nsctp_wait_for_connect() drops and re-acquires the socket lock while\nwaiting for the association to reach ESTABLISHED state. During this\nwindow, another thread can peeloff the association to a new socket via\ngetsockopt(SCTP_SOCKOPT_PEELOFF), changing asoc-\u003ebase.sk. After\nre-acquiring the old socket lock, sctp_wait_for_connect() returns\nsuccess without noticing the migration \u2014 the caller then accesses\nthe association under the wrong lock in sctp_datamsg_from_user().\n\nAdd the same sk != asoc-\u003ebase.sk check that sctp_wait_for_sndbuf()\nalready has, returning an error if the association was migrated while\nwe slept."
          }
        ],
        "id": "CVE-2026-63971",
        "lastModified": "2026-07-30T14:51:11.223",
        "metrics": {
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              "cvssData": {
                "attackComplexity": "LOW",
                "attackVector": "LOCAL",
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                "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"
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              "exploitabilityScore": 1.8,
              "impactScore": 5.9,
              "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
              "type": "Secondary"
            }
          ]
        },
        "published": "2026-07-19T16:17:16.163",
        "references": [
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          },
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          {
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        "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "vulnStatus": "Awaiting Analysis"
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    "redhat_vex": {
      "aggregate_severity": "Moderate",
      "current_release_date": "2026-09-14T11:48:08+00:00",
      "cve": "CVE-2026-63971",
      "id": "CVE-2026-63971",
      "initial_release_date": "2026-07-19T00:00:00+00:00",
      "product_status:fixed": "453",
      "product_status:known_affected": "112",
      "product_status:known_not_affected": "28",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: sctp: fix race between sctp_wait_for_connect and peeloff",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-63971.json",
      "version": "3"
    },
    "suse_vex": {
      "aggregate_severity": "important",
      "current_release_date": "2026-09-18T00:45:36Z",
      "cve": "CVE-2026-63971",
      "id": "CVE-2026-63971",
      "initial_release_date": "2026-07-21T13:02:28Z",
      "product_status:first_fixed": "2",
      "product_status:known_affected": "578",
      "product_status:recommended": "503",
      "source": "SUSE CSAF VEX",
      "status": "interim",
      "title": "SUSE CVE CVE-2026-63971",
      "url": "https://ftp.suse.com/pub/projects/security/csaf-vex/cve-2026-63971.json",
      "version": "19"
    }
  }
}



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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.


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.