CVE-2026-98383 (GCVE-0-2026-98383)
Vulnerability from cvelistv5
Published
2026-10-09 07:34
Modified
2026-10-24 14:08
Severity ?
7.8 (High) - CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Summary
In the Linux kernel, the following vulnerability has been resolved: bpf: Disallow bpf_skb_pull_data() for LWT_SEG6LOCAL An LWT_SEG6LOCAL program can invalidate its cached SRH with bpf_lwt_seg6_adjust_srh() and then call bpf_skb_pull_data(). The latter may reallocate skb->head, leaving the per-CPU SRH pointer dangling. Post-program SRH validation then writes through that pointer. Disallow bpf_skb_pull_data() for LWT_SEG6LOCAL programs so the verifier rejects this unsafe helper combination. Other LWT program types continue to expose the helper through lwt_out_func_proto().
References
Impacted products
Vendor Product Version
Linux Linux Version: 004d4b274e2a1a895a0e5dc66158b90a7d463d44
Version: 004d4b274e2a1a895a0e5dc66158b90a7d463d44
Version: 004d4b274e2a1a895a0e5dc66158b90a7d463d44
Version: 004d4b274e2a1a895a0e5dc66158b90a7d463d44
Version: 004d4b274e2a1a895a0e5dc66158b90a7d463d44
Version: 004d4b274e2a1a895a0e5dc66158b90a7d463d44
Version: 004d4b274e2a1a895a0e5dc66158b90a7d463d44
Version: 004d4b274e2a1a895a0e5dc66158b90a7d463d44
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{
  "containers": {
    "cna": {
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        {
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          "product": "Linux",
          "programFiles": [
            "net/core/filter.c"
          ],
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          "vendor": "Linux",
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          "product": "Linux",
          "programFiles": [
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          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
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              "version": "4.18"
            },
            {
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              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
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              "status": "unaffected",
              "version": "5.10.271",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "5.15.*",
              "status": "unaffected",
              "version": "5.15.222",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.1.*",
              "status": "unaffected",
              "version": "6.1.189",
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              "status": "unaffected",
              "version": "6.6.158",
              "versionType": "semver"
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              "version": "6.12.112",
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              "status": "unaffected",
              "version": "6.18.55",
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            },
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              "lessThanOrEqual": "7.2.*",
              "status": "unaffected",
              "version": "7.2.9",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.3",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
            {
              "cpeMatch": [
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                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "5.10.271",
                  "versionStartIncluding": "4.18",
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                  "vulnerable": true
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                  "versionEndExcluding": "7.3",
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                  "vulnerable": true
                }
              ],
              "negate": false,
              "operator": "OR"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nbpf: Disallow bpf_skb_pull_data() for LWT_SEG6LOCAL\n\nAn LWT_SEG6LOCAL program can invalidate its cached SRH with\nbpf_lwt_seg6_adjust_srh() and then call bpf_skb_pull_data(). The latter\nmay reallocate skb-\u003ehead, leaving the per-CPU SRH pointer dangling.\nPost-program SRH validation then writes through that pointer.\n\nDisallow bpf_skb_pull_data() for LWT_SEG6LOCAL programs so the verifier\nrejects this unsafe helper combination. Other LWT program types continue\nto expose the helper through lwt_out_func_proto()."
        }
      ],
      "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 local bpf(BPF_PROG_LOAD) path reaches check_helper_call() and the patched lwt_seg6local_func_proto(), where attacker-authored bytecode requests bpf_lwt_seg6_adjust_srh() and bpf_skb_pull_data(); an RTM_NEWROUTE then attaches it. A received SRH packet merely executes that installed program and cannot create the unsafe helper sequence.\nAC:L - The attacker controls the helper order, SRH offset and length, and can inject a large non-linear SRv6 frame so bpf_skb_pull_data() deterministically reaches __pskb_pull_tail() and pskb_expand_head(). No race is required, and repeated packets reproduce the stale-pointer write.\nPR:L - bpf_prog_load() requires CAP_BPF and CAP_NET_ADMIN for BPF_PROG_TYPE_LWT_SEG6LOCAL, but BPF_F_TOKEN_FD and bpf_token_capable() support delegating both into a user namespace; rtnetlink_rcv_msg() separately accepts CAP_NET_ADMIN in the route\u0027s network namespace. Thus a host-unprivileged token holder can perform the complete setup.\nUI:N - The attacker loads the program, installs the End.BPF route, and injects the triggering SRv6 frame without any victim action.\nS:U - The stale srh pointer and resulting corruption occur in the same host kernel that processes the attacker\u0027s BPF program and packet; no VM, IOMMU, or other security-authority boundary is crossed.\nC:H - After skb-\u003ehead is freed, seg6_bpf_has_valid_srh() passes the dangling srh pointer to seg6_validate_srh(), which reads header fields and variable-length TLVs from reusable slab memory; its drop-versus-forward result also provides an observable contents oracle.\nI:H - seg6_bpf_has_valid_srh() executes srh-\u003ehdrlen = srh_state-\u003ehdrlen \u003e\u003e 3 through the dangling pointer, producing an attacker-valued one-byte write into freed slab memory that can corrupt a reclaimed object or allocator state and support control-flow compromise.\nA:H - The stale write in seg6_bpf_has_valid_srh() is a confirmed slab use-after-free and can trigger a KASAN panic or later kernel oops through corrupted freed-object state; the attacker can repeat it with additional packets."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-10-24T14:08:40.964Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/0f38472a2aa8704a6b514c0dfa9c32f3672b8f32"
        },
        {
          "url": "https://git.kernel.org/stable/c/cae8674489f26edf7553fdd660599466cbb4c32f"
        },
        {
          "url": "https://git.kernel.org/stable/c/9f9e57b5a3a033f95f49ef9d541340cdbcb80abb"
        },
        {
          "url": "https://git.kernel.org/stable/c/df0072be6fc373cb22f9ea854d458b04e32a03cf"
        },
        {
          "url": "https://git.kernel.org/stable/c/b9bb0e735460751b620156f800a4279a28573392"
        },
        {
          "url": "https://git.kernel.org/stable/c/37b18688cd18fd86d2f35c212df1611862a26cd5"
        },
        {
          "url": "https://git.kernel.org/stable/c/fca71ead7a20290af1e2046983eeafae43d21af1"
        },
        {
          "url": "https://git.kernel.org/stable/c/e4a62833adff6ef0fe7c0b90393204fe3c26b5c5"
        }
      ],
      "title": "bpf: Disallow bpf_skb_pull_data() for LWT_SEG6LOCAL",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-98383",
    "datePublished": "2026-10-09T07:34:22.408Z",
    "dateReserved": "2026-09-25T10:25:14.345Z",
    "dateUpdated": "2026-10-24T14:08:40.964Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}


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