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CVE-2026-72400 (GCVE-0-2026-72400)

Vulnerability from cvelistv5 – Published: 2026-08-15 05:56 – Updated: 2026-08-17 05:43
VLAI
Title
seg6: validate SRH length before reading fixed fields
Summary
In the Linux kernel, the following vulnerability has been resolved: seg6: validate SRH length before reading fixed fields seg6_validate_srh() reads fixed SRH fields such as srh->type and srh->hdrlen before checking that the supplied length covers the fixed struct ipv6_sr_hdr fields. The BPF SEG6 encap path reaches this with a BPF program-supplied pointer and length: bpf_lwt_push_encap() and the SEG6 local BPF END_B6 and END_B6_ENCAP actions call bpf_push_seg6_encap(), which forwards the length to seg6_validate_srh() with no minimum-size guard. A 2-byte SEG6 encap header can therefore make the validator read srh->type at offset 2 beyond the caller-supplied buffer. Reject lengths shorter than the fixed SRH at the top of seg6_validate_srh(), before any field is read. This fixes the BPF helper path and keeps the common validator robust.
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: fe94cc290f535709d3c5ebd1e472dfd0aec7ee79 , < 715eb12e453df752f1b4baaf972c3acff0ab9402 (git)
Affected: fe94cc290f535709d3c5ebd1e472dfd0aec7ee79 , < 7247d05c987c3eec4bb7c2306dbd77ecdf3b7c73 (git)
Affected: fe94cc290f535709d3c5ebd1e472dfd0aec7ee79 , < 071f1a38d7ddbadee29c09b9e3ee0ff3a61e6a0e (git)
Affected: fe94cc290f535709d3c5ebd1e472dfd0aec7ee79 , < 804bb969f194c93497ba632b98343794c6367fdc (git)
Affected: fe94cc290f535709d3c5ebd1e472dfd0aec7ee79 , < 0fc7069d39239978130c37ebceaec85c8948d3f1 (git)
Affected: fe94cc290f535709d3c5ebd1e472dfd0aec7ee79 , < 8dba7a94a269b88e500aafc25ad567ef6a423698 (git)
Affected: fe94cc290f535709d3c5ebd1e472dfd0aec7ee79 , < c9961336aa5ff83092f23e33ee86666a9dbd1b2a (git)
Affected: fe94cc290f535709d3c5ebd1e472dfd0aec7ee79 , < a75d99f46bf21b45965ce39c5cfb3b8bb5ffb1aa (git)
guessed Create a notification for this product.
Linux Linux Affected: 4.18
Unaffected: 0 , < 4.18 (semver)
Unaffected: 5.10.261 , ≤ 5.10.* (semver)
Unaffected: 5.15.212 , ≤ 5.15.* (semver)
Unaffected: 6.1.178 , ≤ 6.1.* (semver)
Unaffected: 6.6.145 , ≤ 6.6.* (semver)
Unaffected: 6.12.97 , ≤ 6.12.* (semver)
Unaffected: 6.18.40 , ≤ 6.18.* (semver)
Unaffected: 7.1.5 , ≤ 7.1.* (semver)
Unaffected: 7.2 , ≤ * (original_commit_for_fix)
guessed Create a notification for this product.
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        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nseg6: validate SRH length before reading fixed fields\n\nseg6_validate_srh() reads fixed SRH fields such as srh-\u003etype and\nsrh-\u003ehdrlen before checking that the supplied length covers the fixed\nstruct ipv6_sr_hdr fields.\n\nThe BPF SEG6 encap path reaches this with a BPF program-supplied pointer\nand length: bpf_lwt_push_encap() and the SEG6 local BPF END_B6 and\nEND_B6_ENCAP actions call bpf_push_seg6_encap(), which forwards the\nlength to seg6_validate_srh() with no minimum-size guard.  A 2-byte SEG6\nencap header can therefore make the validator read srh-\u003etype at offset 2\nbeyond the caller-supplied buffer.\n\nReject lengths shorter than the fixed SRH at the top of\nseg6_validate_srh(), before any field is read.  This fixes the BPF helper\npath and keeps the common validator robust."
        }
      ],
      "metrics": [
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            "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"
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              "value": "AV:L - Exploitation requires loading BPF LWT SEG6 programs and attaching SRv6 routes via bpf() and RTNETLINK; the OOB read is triggered through bpf_lwt_push_encap/bpf_lwt_seg6_action helpers, not by remote IPv6 packet parsing alone.\nAC:L - An attacker with route/BPF setup privileges can deterministically call bpf_push_seg6_encap() or bpf_lwt_seg6_action(END_B6/END_B6_ENCAP) with a 2-byte buffer, immediately forcing seg6_validate_srh() to read fixed SRH fields past the buffer end.\nPR:L - Loading BPF_PROG_TYPE_LWT_IN/LWT_SEG6LOCAL and installing SRv6 LWT routes requires CAP_NET_ADMIN, obtainable by unprivileged users inside user/network namespaces (unshare -Urn), not only init-namespace root.\nUI:N - No victim interaction is required; triggering the bug needs only attacker-controlled BPF execution during SRv6/LWT packet processing after the attacker configures routes and programs.\nS:U - Impact is confined to kernel memory safety within the same host security boundary; there is no VM escape, sandbox breakout, or cross-authority scope change beyond standard local kernel compromise.\nC:H - seg6_validate_srh() performs out-of-bounds reads of SRH header bytes (e.g., srh-\u003etype at offset 2) beyond the attacker-supplied length, disclosing adjacent kernel/BPF stack memory that may include pointers and sensitive metadata.\nI:H - Kernel out-of-bounds reads in this validation path constitute memory-safety corruption that can be chained with disclosed pointers and heap/stack layout control from BPF context to obtain arbitrary write or code-execution primitives.\nA:H - Undersized SRH buffers can cause seg6_validate_srh() to read past mapped BPF/kernel memory and trigger kernel faults, oops, or panic on SRv6 routers processing attacker-driven BPF SEG6 encap traffic."
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        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
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    "datePublished": "2026-08-15T05:56:25.572Z",
    "dateReserved": "2026-08-09T03:40:39.925Z",
    "dateUpdated": "2026-08-17T05:43:42.988Z",
    "state": "PUBLISHED"
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A 2-byte SEG6\\nencap header can therefore make the validator read srh-\u003etype at offset 2\\nbeyond the caller-supplied buffer.\\n\\nReject lengths shorter than the fixed SRH at the top of\\nseg6_validate_srh(), before any field is read.  This fixes the BPF helper\\npath and keeps the common validator robust.\"}],\"affected\":[{\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"affectedData\":[{\"vendor\":\"Linux\",\"product\":\"Linux\",\"defaultStatus\":\"unaffected\",\"programFiles\":[\"net/ipv6/seg6.c\"],\"repo\":\"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\"versions\":[{\"version\":\"fe94cc290f535709d3c5ebd1e472dfd0aec7ee79\",\"lessThan\":\"715eb12e453df752f1b4baaf972c3acff0ab9402\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"fe94cc290f535709d3c5ebd1e472dfd0aec7ee79\",\"lessThan\":\"7247d05c987c3eec4bb7c2306dbd77ecdf3b7c73\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"fe94cc290f535709d3c5ebd1e472dfd0aec7ee79\",\"lessThan\":\"071f1a38d7ddbadee29c09b9e3ee0ff3a61e6a0e\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"fe94cc290f535709d3c5ebd1e472dfd0aec7ee79\",\"lessThan\":\"804bb969f194c93497ba632b98343794c6367fdc\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"fe94cc290f535709d3c5ebd1e472dfd0aec7ee79\",\"lessThan\":\"0fc7069d39239978130c37ebceaec85c8948d3f1\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"fe94cc290f535709d3c5ebd1e472dfd0aec7ee79\",\"lessThan\":\"8dba7a94a269b88e500aafc25ad567ef6a423698\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"fe94cc290f535709d3c5ebd1e472dfd0aec7ee79\",\"lessThan\":\"c9961336aa5ff83092f23e33ee86666a9dbd1b2a\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"fe94cc290f535709d3c5ebd1e472dfd0aec7ee79\",\"lessThan\":\"a75d99f46bf21b45965ce39c5cfb3b8bb5ffb1aa\",\"versionType\":\"git\",\"status\":\"affected\"}]},{\"vendor\":\"Linux\",\"product\":\"Linux\",\"defaultStatus\":\"affected\",\"programFiles\":[\"net/ipv6/seg6.c\"],\"repo\":\"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\"versions\":[{\"version\":\"4.18\",\"status\":\"affected\"},{\"version\":\"0\",\"lessThan\":\"4.18\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"5.10.261\",\"lessThanOrEqual\":\"5.10.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"5.15.212\",\"lessThanOrEqual\":\"5.15.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"6.1.178\",\"lessThanOrEqual\":\"6.1.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"6.6.145\",\"lessThanOrEqual\":\"6.6.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"6.12.97\",\"lessThanOrEqual\":\"6.12.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"6.18.40\",\"lessThanOrEqual\":\"6.18.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"7.1.5\",\"lessThanOrEqual\":\"7.1.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"7.2\",\"lessThanOrEqual\":\"*\",\"versionType\":\"original_commit_for_fix\",\"status\":\"unaffected\"}]}]}],\"metrics\":{\"cvssMetricV31\":[{\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"type\":\"Secondary\",\"cvssData\":{\"version\":\"3.1\",\"vectorString\":\"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H\",\"baseScore\":7.8,\"baseSeverity\":\"HIGH\",\"attackVector\":\"LOCAL\",\"attackComplexity\":\"LOW\",\"privilegesRequired\":\"LOW\",\"userInteraction\":\"NONE\",\"scope\":\"UNCHANGED\",\"confidentialityImpact\":\"HIGH\",\"integrityImpact\":\"HIGH\",\"availabilityImpact\":\"HIGH\"},\"exploitabilityScore\":1.8,\"impactScore\":5.9}]},\"references\":[{\"url\":\"https://git.kernel.org/stable/c/071f1a38d7ddbadee29c09b9e3ee0ff3a61e6a0e\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/0fc7069d39239978130c37ebceaec85c8948d3f1\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/715eb12e453df752f1b4baaf972c3acff0ab9402\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/7247d05c987c3eec4bb7c2306dbd77ecdf3b7c73\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/804bb969f194c93497ba632b98343794c6367fdc\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/8dba7a94a269b88e500aafc25ad567ef6a423698\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/a75d99f46bf21b45965ce39c5cfb3b8bb5ffb1aa\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/c9961336aa5ff83092f23e33ee86666a9dbd1b2a\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"}]}}",
    "redhat_vex": {
      "aggregate_severity": "Moderate",
      "current_release_date": "2026-08-19T07:18:46+00:00",
      "cve": "CVE-2026-72400",
      "id": "CVE-2026-72400",
      "initial_release_date": "2026-08-15T00:00:00+00:00",
      "product_status:known_affected": "232",
      "product_status:known_not_affected": "42",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: seg6: validate SRH length before reading fixed fields",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-72400.json",
      "version": "3"
    }
  }
}



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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.

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  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
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