CVE-2026-31684 (GCVE-0-2026-31684)

Vulnerability from cvelistv5 – Published: 2026-04-25 08:47 – Updated: 2026-04-27 13:57
VLAI?
Title
net: sched: act_csum: validate nested VLAN headers
Summary
In the Linux kernel, the following vulnerability has been resolved: net: sched: act_csum: validate nested VLAN headers tcf_csum_act() walks nested VLAN headers directly from skb->data when an skb still carries in-payload VLAN tags. The current code reads vlan->h_vlan_encapsulated_proto and then pulls VLAN_HLEN bytes without first ensuring that the full VLAN header is present in the linear area. If only part of an inner VLAN header is linearized, accessing h_vlan_encapsulated_proto reads past the linear area, and the following skb_pull(VLAN_HLEN) may violate skb invariants. Fix this by requiring pskb_may_pull(skb, VLAN_HLEN) before accessing and pulling each nested VLAN header. If the header still is not fully available, drop the packet through the existing error path.
Severity ?
No CVSS data available.
Assigner
References
Impacted products
Vendor Product Version
Linux Linux Affected: 2ecba2d1e45b24620a7c3df9531895cf68d5dec6 , < eb3765b90eb8f2a3d6310a80c14a9e57ec4267a2 (git)
Affected: 2ecba2d1e45b24620a7c3df9531895cf68d5dec6 , < a69738efea0996d05a3c7d2178551b891744df1b (git)
Affected: 2ecba2d1e45b24620a7c3df9531895cf68d5dec6 , < ec4930979b3f7bbeb7af5744599fc6603a4dba62 (git)
Affected: 2ecba2d1e45b24620a7c3df9531895cf68d5dec6 , < 3d165d975305cf76ff0b10a3c798fb31e5f5f9a5 (git)
Affected: 2ecba2d1e45b24620a7c3df9531895cf68d5dec6 , < c842743d073bdd683606cb414eb0ca84465dd834 (git)
Affected: 3764bfae5056e95617b6ee074129297e11710886 (git)
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    Linux Linux Affected: 5.1
Unaffected: 0 , < 5.1 (semver)
Unaffected: 6.6.136 , ≤ 6.6.* (semver)
Unaffected: 6.12.83 , ≤ 6.12.* (semver)
Unaffected: 6.18.24 , ≤ 6.18.* (semver)
Unaffected: 6.19.14 , ≤ 6.19.* (semver)
Unaffected: 7.0 , ≤ * (original_commit_for_fix)
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{
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          "programFiles": [
            "net/sched/act_csum.c"
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          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet: sched: act_csum: validate nested VLAN headers\n\ntcf_csum_act() walks nested VLAN headers directly from skb-\u003edata when an\nskb still carries in-payload VLAN tags. The current code reads\nvlan-\u003eh_vlan_encapsulated_proto and then pulls VLAN_HLEN bytes without\nfirst ensuring that the full VLAN header is present in the linear area.\n\nIf only part of an inner VLAN header is linearized, accessing\nh_vlan_encapsulated_proto reads past the linear area, and the following\nskb_pull(VLAN_HLEN) may violate skb invariants.\n\nFix this by requiring pskb_may_pull(skb, VLAN_HLEN) before accessing and\npulling each nested VLAN header. If the header still is not fully\navailable, drop the packet through the existing error path."
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-04-27T13:57:15.059Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
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      "title": "net: sched: act_csum: validate nested VLAN headers",
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    "assignerShortName": "Linux",
    "cveId": "CVE-2026-31684",
    "datePublished": "2026-04-25T08:47:01.555Z",
    "dateReserved": "2026-03-09T15:48:24.130Z",
    "dateUpdated": "2026-04-27T13:57:15.059Z",
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  }
}


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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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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.
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  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.



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