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GHSA-R749-JHCJ-5X93

Vulnerability from github – Published: 2026-08-10 15:33 – Updated: 2026-08-10 15:33

Details

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

bpf: Reject redirect helpers without a bpf_net_context

The bpf_redirect() helpers and skb_do_redirect() obtain the per-task bpf_redirect_info via bpf_net_ctx_get_ri(), which dereferences the current->bpf_net_context unconditionally. That context is established on the paths that run tc BPF such as sch_handle_{ingress,egress}(), except* for the case where {cls,act}_bpf was attached to a proper qdisc. A program running from there reaches the NULL deref in two ways:

It calls bpf_redirect() directly, which dereferences the context at the top of the helper:

tc qdisc add dev eth0 root handle 1: red limit 1MB min 10KB max 20KB \ avpkt 1000 burst 100 qevent early_drop block 10 tc filter add block 10 pref 1 bpf obj redirect.o
It simply returns TC_ACT_REDIRECT without helper call: tcf_qevent_handle() then dispatches to skb_do_redirect(), which dereferences the context

Rather than extending bpf_net_context management into the qdisc path, make the redirect helpers refuse to operate when no context exists, and have tcf_qevent_handle() drop a TC_ACT_REDIRECT verdict instead of calling skb_do_redirect(). Previous behaviour was a crash, so nothing regresses by not supporting it.

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{
  "affected": [],
  "aliases": [
    "CVE-2026-68337"
  ],
  "database_specific": {
    "cwe_ids": [],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-08-10T13:20:24Z",
    "severity": null
  },
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nbpf: Reject redirect helpers without a bpf_net_context\n\nThe bpf_redirect*() helpers and skb_do_redirect() obtain the per-task\nbpf_redirect_info via bpf_net_ctx_get_ri(), which dereferences the\ncurrent-\u003ebpf_net_context unconditionally. That context is established\non the paths that run tc BPF such as sch_handle_{ingress,egress}(),\n*except* for the case where {cls,act}_bpf was attached to a proper\nqdisc. A program running from there reaches the NULL deref in two ways:\n\n* It calls bpf_redirect() directly, which dereferences the context at\n  the top of the helper:\n\n     tc qdisc add dev eth0 root handle 1: red limit 1MB min 10KB max 20KB \\\n        avpkt 1000 burst 100 qevent early_drop block 10\n     tc filter add block 10 pref 1 bpf obj redirect.o\n\n* It simply returns TC_ACT_REDIRECT without helper call: tcf_qevent_handle()\n  then dispatches to skb_do_redirect(), which dereferences the context\n\nRather than extending bpf_net_context management into the qdisc path,\nmake the redirect helpers refuse to operate when no context exists, and\nhave tcf_qevent_handle() drop a TC_ACT_REDIRECT verdict instead of\ncalling skb_do_redirect(). Previous behaviour was a crash, so nothing\nregresses by not supporting it.",
  "id": "GHSA-r749-jhcj-5x93",
  "modified": "2026-08-10T15:33:46Z",
  "published": "2026-08-10T15:33:46Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-68337"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/3f4920d165b29052255527d8ae7619e7ec132ece"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/cabfacbd5af09d3ae898ca224c4a1459e9bba15d"
    }
  ],
  "schema_version": "1.4.0",
  "severity": []
}

CVE-2026-68337 (GCVE-0-2026-68337)

Vulnerability from cvelistv5 – Published: 2026-08-10 12:03 – Updated: 2026-08-17 05:03

Title

bpf: Reject redirect helpers without a bpf_net_context

Summary

In the Linux kernel, the following vulnerability has been resolved: bpf: Reject redirect helpers without a bpf_net_context The bpf_redirect*() helpers and skb_do_redirect() obtain the per-task bpf_redirect_info via bpf_net_ctx_get_ri(), which dereferences the current->bpf_net_context unconditionally. That context is established on the paths that run tc BPF such as sch_handle_{ingress,egress}(), *except* for the case where {cls,act}_bpf was attached to a proper qdisc. A program running from there reaches the NULL deref in two ways: * It calls bpf_redirect() directly, which dereferences the context at the top of the helper: tc qdisc add dev eth0 root handle 1: red limit 1MB min 10KB max 20KB \ avpkt 1000 burst 100 qevent early_drop block 10 tc filter add block 10 pref 1 bpf obj redirect.o * It simply returns TC_ACT_REDIRECT without helper call: tcf_qevent_handle() then dispatches to skb_do_redirect(), which dereferences the context Rather than extending bpf_net_context management into the qdisc path, make the redirect helpers refuse to operate when no context exists, and have tcf_qevent_handle() drop a TC_ACT_REDIRECT verdict instead of calling skb_do_redirect(). Previous behaviour was a crash, so nothing regresses by not supporting it.

Severity

No CVSS data available.

Assigner

Linux mitre root

References

2 references

URL	Tags
https://git.kernel.org/stable/c/cabfacbd5af09d3ae…
https://git.kernel.org/stable/c/3f4920d165b290522…

Impacted products

2 products

Vendor	Product	Version
Linux	Linux	Affected: 3625750f05ecce21a0fce429c1ff85acfffb461b , < cabfacbd5af09d3ae898ca224c4a1459e9bba15d (git) Affected: 3625750f05ecce21a0fce429c1ff85acfffb461b , < 3f4920d165b29052255527d8ae7619e7ec132ece (git)
Linux	Linux	Affected: 5.9 Unaffected: 0 , < 5.9 (semver) Unaffected: 7.1.6 , ≤ 7.1.* (semver) Unaffected: 7.2 , ≤ * (original_commit_for_fix)

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{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "net/core/filter.c",
            "net/sched/cls_api.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
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              "versionType": "git"
            },
            {
              "lessThan": "3f4920d165b29052255527d8ae7619e7ec132ece",
              "status": "affected",
              "version": "3625750f05ecce21a0fce429c1ff85acfffb461b",
              "versionType": "git"
            }
          ]
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          "programFiles": [
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          "versions": [
            {
              "status": "affected",
              "version": "5.9"
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              "version": "0",
              "versionType": "semver"
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              "versionType": "semver"
            },
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              "version": "7.2",
              "versionType": "original_commit_for_fix"
            }
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        }
      ],
      "cpeApplicability": [
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                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
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                  "vulnerable": true
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          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nbpf: Reject redirect helpers without a bpf_net_context\n\nThe bpf_redirect*() helpers and skb_do_redirect() obtain the per-task\nbpf_redirect_info via bpf_net_ctx_get_ri(), which dereferences the\ncurrent-\u003ebpf_net_context unconditionally. That context is established\non the paths that run tc BPF such as sch_handle_{ingress,egress}(),\n*except* for the case where {cls,act}_bpf was attached to a proper\nqdisc. A program running from there reaches the NULL deref in two ways:\n\n* It calls bpf_redirect() directly, which dereferences the context at\n  the top of the helper:\n\n     tc qdisc add dev eth0 root handle 1: red limit 1MB min 10KB max 20KB \\\n        avpkt 1000 burst 100 qevent early_drop block 10\n     tc filter add block 10 pref 1 bpf obj redirect.o\n\n* It simply returns TC_ACT_REDIRECT without helper call: tcf_qevent_handle()\n  then dispatches to skb_do_redirect(), which dereferences the context\n\nRather than extending bpf_net_context management into the qdisc path,\nmake the redirect helpers refuse to operate when no context exists, and\nhave tcf_qevent_handle() drop a TC_ACT_REDIRECT verdict instead of\ncalling skb_do_redirect(). Previous behaviour was a crash, so nothing\nregresses by not supporting it."
        }
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    "assignerShortName": "Linux",
    "cveId": "CVE-2026-68337",
    "datePublished": "2026-08-10T12:03:13.583Z",
    "dateReserved": "2026-07-30T09:28:09.383Z",
    "dateUpdated": "2026-08-17T05:03:36.374Z",
    "state": "PUBLISHED"
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}

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.

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.

Action not permitted

GHSA-R749-JHCJ-5X93

CVE-2026-68337 (GCVE-0-2026-68337)

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Nomenclature