Vulnerability-Lookup

GHSA-39FM-RJR2-46W3

Vulnerability from github – Published: 2026-07-19 18:31 – Updated: 2026-07-20 15:31

Details

In the Linux kernel, the following vulnerability has been resolved:

bpf: sockmap: fix tail fragment offset in bpf_msg_push_data

When bpf_msg_push_data() inserts data in the middle of a scatterlist entry, it splits the original entry into a left fragment and a right fragment.

The right fragment offset is page-local, but the code advances it with start, which is the message-global insertion point. For inserts into a non-first SG entry, this over-advances the offset and leaves the split layout inconsistent.

Advance the right fragment offset by the fragment-local delta, start - offset, which matches the length removed from the front of the original entry.

Severity

8.4 (High)


                  
                    CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

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{
  "affected": [],
  "aliases": [
    "CVE-2026-63926"
  ],
  "database_specific": {
    "cwe_ids": [],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-07-19T16:17:10Z",
    "severity": "HIGH"
  },
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nbpf: sockmap: fix tail fragment offset in bpf_msg_push_data\n\nWhen bpf_msg_push_data() inserts data in the middle of a scatterlist\nentry, it splits the original entry into a left fragment and a right\nfragment.\n\nThe right fragment offset is page-local, but the code advances it with\n`start`, which is the message-global insertion point. For inserts into a\nnon-first SG entry, this over-advances the offset and leaves the split\nlayout inconsistent.\n\nAdvance the right fragment offset by the fragment-local delta,\n`start - offset`, which matches the length removed from the front of the\noriginal entry.",
  "id": "GHSA-39fm-rjr2-46w3",
  "modified": "2026-07-20T15:31:52Z",
  "published": "2026-07-19T18:31:46Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-63926"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/3075c21d2d76c0067f4a382765b43d6cc10470f1"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/5e19028667963fb371ebb00cecc2a473ef92056b"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/63f64a510c7917658ddf4d073ece73914ee25346"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/96b72672ce849a1402730238e64d9b20bf06a96d"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/aeb95146848d12206e1b2cfacd4f40e21ce81d94"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/d81b323af2dcee47573907ccb89c0df9b45cb2e2"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/f14609d8146707452e0822f3c8154674ce677251"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/f72eed9b84fb771019a955908132410a9ba9ea3f"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
      "type": "CVSS_V3"
    }
  ]
}

CVE-2026-63926 (GCVE-0-2026-63926)

Vulnerability from cvelistv5 – Published: 2026-07-19 14:55 – Updated: 2026-08-05 12:37

Title

bpf: sockmap: fix tail fragment offset in bpf_msg_push_data

Summary

In the Linux kernel, the following vulnerability has been resolved: bpf: sockmap: fix tail fragment offset in bpf_msg_push_data When bpf_msg_push_data() inserts data in the middle of a scatterlist entry, it splits the original entry into a left fragment and a right fragment. The right fragment offset is page-local, but the code advances it with `start`, which is the message-global insertion point. For inserts into a non-first SG entry, this over-advances the offset and leaves the split layout inconsistent. Advance the right fragment offset by the fragment-local delta, `start - offset`, which matches the length removed from the front of the original entry.

Severity

8.4 (High)


                        
                          CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Assigner

Linux mitre root Scorecard

References

8 references

URL	Tags
https://git.kernel.org/stable/c/f14609d8146707452…
https://git.kernel.org/stable/c/d81b323af2dcee475…
https://git.kernel.org/stable/c/aeb95146848d12206…
https://git.kernel.org/stable/c/96b72672ce849a140…
https://git.kernel.org/stable/c/3075c21d2d76c0067…
https://git.kernel.org/stable/c/5e19028667963fb37…
https://git.kernel.org/stable/c/63f64a510c7917658…
https://git.kernel.org/stable/c/f72eed9b84fb77101…

Impacted products

2 products

Vendor	Product	Version
Linux	Linux	Affected: 6fff607e2f14bd7c63c06c464a6f93b8efbabe28 , < f14609d8146707452e0822f3c8154674ce677251 (git) Affected: 6fff607e2f14bd7c63c06c464a6f93b8efbabe28 , < d81b323af2dcee47573907ccb89c0df9b45cb2e2 (git) Affected: 6fff607e2f14bd7c63c06c464a6f93b8efbabe28 , < aeb95146848d12206e1b2cfacd4f40e21ce81d94 (git) Affected: 6fff607e2f14bd7c63c06c464a6f93b8efbabe28 , < 96b72672ce849a1402730238e64d9b20bf06a96d (git) Affected: 6fff607e2f14bd7c63c06c464a6f93b8efbabe28 , < 3075c21d2d76c0067f4a382765b43d6cc10470f1 (git) Affected: 6fff607e2f14bd7c63c06c464a6f93b8efbabe28 , < 5e19028667963fb371ebb00cecc2a473ef92056b (git) Affected: 6fff607e2f14bd7c63c06c464a6f93b8efbabe28 , < 63f64a510c7917658ddf4d073ece73914ee25346 (git) Affected: 6fff607e2f14bd7c63c06c464a6f93b8efbabe28 , < f72eed9b84fb771019a955908132410a9ba9ea3f (git)
Linux	Linux	Affected: 4.20 Unaffected: 0 , < 4.20 (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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{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "net/core/filter.c"
          ],
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              "status": "affected",
              "version": "6fff607e2f14bd7c63c06c464a6f93b8efbabe28",
              "versionType": "git"
            },
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            {
              "lessThan": "aeb95146848d12206e1b2cfacd4f40e21ce81d94",
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            {
              "lessThan": "96b72672ce849a1402730238e64d9b20bf06a96d",
              "status": "affected",
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            {
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              "versionType": "git"
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              "lessThan": "5e19028667963fb371ebb00cecc2a473ef92056b",
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            },
            {
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              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
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            {
              "lessThanOrEqual": "5.10.*",
              "status": "unaffected",
              "version": "5.10.259",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "5.15.*",
              "status": "unaffected",
              "version": "5.15.210",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.1.*",
              "status": "unaffected",
              "version": "6.1.176",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.6.*",
              "status": "unaffected",
              "version": "6.6.143",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.12.*",
              "status": "unaffected",
              "version": "6.12.93",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.18.*",
              "status": "unaffected",
              "version": "6.18.35",
              "versionType": "semver"
            },
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              "lessThanOrEqual": "7.0.*",
              "status": "unaffected",
              "version": "7.0.12",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.1",
              "versionType": "original_commit_for_fix"
            }
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        }
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          "nodes": [
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                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
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                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
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                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
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        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nbpf: sockmap: fix tail fragment offset in bpf_msg_push_data\n\nWhen bpf_msg_push_data() inserts data in the middle of a scatterlist\nentry, it splits the original entry into a left fragment and a right\nfragment.\n\nThe right fragment offset is page-local, but the code advances it with\n`start`, which is the message-global insertion point. For inserts into a\nnon-first SG entry, this over-advances the offset and leaves the split\nlayout inconsistent.\n\nAdvance the right fragment offset by the fragment-local delta,\n`start - offset`, which matches the length removed from the front of the\noriginal entry."
        }
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              "lang": "en",
              "value": "AV:L - The bug is reached through the BPF sk_msg/sockmap send path (sendmsg \u2192 tcp_bpf_send_verdict \u2192 sk_psock_msg_verdict \u2192 bpf_msg_push_data), which requires local syscalls and BPF setup; per kernel CNA guidance, BPF/sockmap issues are scored as Local rather than Network.\nAC:L - An attacker who can load a sk_msg BPF program fully controls the insertion offset and can reliably build multi-fragment scatterlist messages (e.g., via large sendmsg/sendfile) to hit the non-first-entry split path; a public PoC demonstrates deterministic triggering without races or external victim state.\nPR:N - While direct exploitation requires CAP_NET_ADMIN+CAP_BPF to load sockmap/sk_msg programs (obtainable as PR:L via user namespaces), the highest-impact reasonable scenario is an unauthenticated remote client triggering a pre-deployed internet-facing kTLS/sockmap proxy whose sk_msg BPF calls bpf_msg_push_data during outbound processing, requiring no privileges on the victim host.\nUI:N - Exploitation requires no victim user interaction beyond normal network I/O to a service that already runs sockmap/sk_msg BPF; the attacker does not need the victim to mount filesystems, open files, or take other deliberate actions.\nS:U - Impact is kernel heap memory corruption within the same kernel security authority (privilege escalation, memory disclosure, or crash), not a cross-boundary escape such as VM guest-to-host or IOMMU bypass.\nC:H - The incorrect rsge.offset over-advances the page-local offset for non-first scatterlist fragments, causing out-of-bounds reads when subsequent helpers (e.g., bpf_msg_pull_data via sg_virt/memcpy) or the TCP send path consume the corrupted entry; the public PoC shows a 32,752-byte OOB read/UAF.\nI:H - Scatterlist metadata corruption produces inconsistent length/offset pairs that can drive out-of-bounds kernel memory access and is a standard heap corruption primitive potentially weaponizable for arbitrary write or control-flow hijack, not merely a bounded data error.\nA:H - Corrupted scatterlist state can cause kernel oops/panic from out-of-bounds page access (as shown in the PoC KASAN trace) or destabilize subsequent sk_msg/TCP/kTLS transmit processing, resulting in denial of service."
            }
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      "providerMetadata": {
        "dateUpdated": "2026-08-05T12:37:21.277Z",
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        {
          "url": "https://git.kernel.org/stable/c/f72eed9b84fb771019a955908132410a9ba9ea3f"
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      "title": "bpf: sockmap: fix tail fragment offset in bpf_msg_push_data",
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    "cveId": "CVE-2026-63926",
    "datePublished": "2026-07-19T14:55:27.154Z",
    "dateReserved": "2026-07-19T07:54:57.021Z",
    "dateUpdated": "2026-08-05T12:37:21.277Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}

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.

The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base model, served locally by ML-Gateway. They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
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GHSA-39FM-RJR2-46W3

CVE-2026-63926 (GCVE-0-2026-63926)

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