Vulnerability-Lookup

GHSA-5J52-34GV-X96C

Vulnerability from github – Published: 2026-08-15 06:32 – Updated: 2026-08-17 06:33

Details

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

netfilter: xt_connmark: reject invalid shift parameters

Revision 2 of the CONNMARK target accepts user-controlled shift parameters and applies them to 32-bit mark values in connmark_tg_shift().

A shift_bits value of 32 or more triggers an undefined-shift bug when the rule is evaluated. Invalid shift_dir values are also accepted and silently fall back to the left-shift path.

Reject invalid revision-2 shift parameters in connmark_tg_check() so malformed rules fail at installation time, before they can reach the packet path.

Severity

7.3 (High)


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

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{
  "affected": [],
  "aliases": [
    "CVE-2026-72347"
  ],
  "database_specific": {
    "cwe_ids": [],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-08-15T06:22:08Z",
    "severity": "HIGH"
  },
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nnetfilter: xt_connmark: reject invalid shift parameters\n\nRevision 2 of the CONNMARK target accepts user-controlled shift\nparameters and applies them to 32-bit mark values in\nconnmark_tg_shift().\n\nA shift_bits value of 32 or more triggers an undefined-shift bug when\nthe rule is evaluated. Invalid shift_dir values are also accepted and\nsilently fall back to the left-shift path.\n\nReject invalid revision-2 shift parameters in connmark_tg_check() so\nmalformed rules fail at installation time, before they can reach the\npacket path.",
  "id": "GHSA-5j52-34gv-x96c",
  "modified": "2026-08-17T06:33:24Z",
  "published": "2026-08-15T06:32:21Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-72347"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/1b47026fb4b35bac850ad6e8a4ad7fc018e09ebc"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/230173cc6105bdfb2696d37e6e56687b003fbe63"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/4eef84b09a3836919360c4232b0f16651a155eec"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/8ace320ac4416f5e5fbcd065309fb2dfcce787b0"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/9657bb11a6376ab0a79f05d433713d6944111e9d"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/c3fa852d117b3fda72265e4230e3967db4a74fcf"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/d8ce63d928b457fba7ed1e302492dfd32293671c"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:L/I:H/A:H",
      "type": "CVSS_V3"
    }
  ]
}

CVE-2026-72347 (GCVE-0-2026-72347)

Vulnerability from cvelistv5 – Published: 2026-08-15 05:55 – Updated: 2026-08-17 05:43

Title

netfilter: xt_connmark: reject invalid shift parameters

Summary

In the Linux kernel, the following vulnerability has been resolved: netfilter: xt_connmark: reject invalid shift parameters Revision 2 of the CONNMARK target accepts user-controlled shift parameters and applies them to 32-bit mark values in connmark_tg_shift(). A shift_bits value of 32 or more triggers an undefined-shift bug when the rule is evaluated. Invalid shift_dir values are also accepted and silently fall back to the left-shift path. Reject invalid revision-2 shift parameters in connmark_tg_check() so malformed rules fail at installation time, before they can reach the packet path.

Severity

7.3 (High)


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

Assigner

Linux mitre root Scorecard

References

7 references

URL	Tags
https://git.kernel.org/stable/c/d8ce63d928b457fba…
https://git.kernel.org/stable/c/9657bb11a6376ab0a…
https://git.kernel.org/stable/c/8ace320ac4416f5e5…
https://git.kernel.org/stable/c/c3fa852d117b3fda7…
https://git.kernel.org/stable/c/4eef84b09a3836919…
https://git.kernel.org/stable/c/230173cc6105bdfb2…
https://git.kernel.org/stable/c/1b47026fb4b35bac8…

Impacted products

2 products

Vendor	Product	Version
Linux	Linux	Affected: 472a73e00757b971d613d796374d2727b2e4954d , < d8ce63d928b457fba7ed1e302492dfd32293671c (git) Affected: 472a73e00757b971d613d796374d2727b2e4954d , < 9657bb11a6376ab0a79f05d433713d6944111e9d (git) Affected: 472a73e00757b971d613d796374d2727b2e4954d , < 8ace320ac4416f5e5fbcd065309fb2dfcce787b0 (git) Affected: 472a73e00757b971d613d796374d2727b2e4954d , < c3fa852d117b3fda72265e4230e3967db4a74fcf (git) Affected: 472a73e00757b971d613d796374d2727b2e4954d , < 4eef84b09a3836919360c4232b0f16651a155eec (git) Affected: 472a73e00757b971d613d796374d2727b2e4954d , < 230173cc6105bdfb2696d37e6e56687b003fbe63 (git) Affected: 472a73e00757b971d613d796374d2727b2e4954d , < 1b47026fb4b35bac850ad6e8a4ad7fc018e09ebc (git)
Linux	Linux	Affected: 4.17 Unaffected: 0 , < 4.17 (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)

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{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "net/netfilter/xt_connmark.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "d8ce63d928b457fba7ed1e302492dfd32293671c",
              "status": "affected",
              "version": "472a73e00757b971d613d796374d2727b2e4954d",
              "versionType": "git"
            },
            {
              "lessThan": "9657bb11a6376ab0a79f05d433713d6944111e9d",
              "status": "affected",
              "version": "472a73e00757b971d613d796374d2727b2e4954d",
              "versionType": "git"
            },
            {
              "lessThan": "8ace320ac4416f5e5fbcd065309fb2dfcce787b0",
              "status": "affected",
              "version": "472a73e00757b971d613d796374d2727b2e4954d",
              "versionType": "git"
            },
            {
              "lessThan": "c3fa852d117b3fda72265e4230e3967db4a74fcf",
              "status": "affected",
              "version": "472a73e00757b971d613d796374d2727b2e4954d",
              "versionType": "git"
            },
            {
              "lessThan": "4eef84b09a3836919360c4232b0f16651a155eec",
              "status": "affected",
              "version": "472a73e00757b971d613d796374d2727b2e4954d",
              "versionType": "git"
            },
            {
              "lessThan": "230173cc6105bdfb2696d37e6e56687b003fbe63",
              "status": "affected",
              "version": "472a73e00757b971d613d796374d2727b2e4954d",
              "versionType": "git"
            },
            {
              "lessThan": "1b47026fb4b35bac850ad6e8a4ad7fc018e09ebc",
              "status": "affected",
              "version": "472a73e00757b971d613d796374d2727b2e4954d",
              "versionType": "git"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "net/netfilter/xt_connmark.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "4.17"
            },
            {
              "lessThan": "4.17",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "5.15.*",
              "status": "unaffected",
              "version": "5.15.212",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.1.*",
              "status": "unaffected",
              "version": "6.1.178",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.6.*",
              "status": "unaffected",
              "version": "6.6.145",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.12.*",
              "status": "unaffected",
              "version": "6.12.97",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.18.*",
              "status": "unaffected",
              "version": "6.18.40",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "7.1.*",
              "status": "unaffected",
              "version": "7.1.5",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.2",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "cpeApplicability": [
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          "nodes": [
            {
              "cpeMatch": [
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                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "5.15.212",
                  "versionStartIncluding": "4.17",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.1.178",
                  "versionStartIncluding": "4.17",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
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                {
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                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
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                  "versionStartIncluding": "4.17",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
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                  "versionStartIncluding": "4.17",
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                {
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          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnetfilter: xt_connmark: reject invalid shift parameters\n\nRevision 2 of the CONNMARK target accepts user-controlled shift\nparameters and applies them to 32-bit mark values in\nconnmark_tg_shift().\n\nA shift_bits value of 32 or more triggers an undefined-shift bug when\nthe rule is evaluated. Invalid shift_dir values are also accepted and\nsilently fall back to the left-shift path.\n\nReject invalid revision-2 shift parameters in connmark_tg_check() so\nmalformed rules fail at installation time, before they can reach the\npacket path."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "baseScore": 7.3,
            "baseSeverity": "HIGH",
            "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:L/I:H/A:H",
            "version": "3.1"
          },
          "scenarios": [
            {
              "lang": "en",
              "value": "AV:L - Malformed CONNMARK rev2 rules are installed via IPT_SO_SET_REPLACE setsockopt or nftables NFNetlink (nft_compat); per kernel CNA guidance netfilter/xtables rule setup is Local even though installed rules later evaluate on ingress/egress packets through ipt_do_table/ip6t_do_table.\nAC:L - The attacker fully controls shift_bits and shift_dir in xt_connmark_tginfo2 when installing the rev2 CONNMARK target and can send conntrack-tracked packets to reliably hit connmark_tg_shift(); no race, memory layout, or victim state outside attacker control is required.\nPR:L - Installing CONNMARK iptables/nftables rules requires CAP_NET_ADMIN in the target network namespace, obtainable by unprivileged users via unshare -Urn; ip_tables.c do_ipt_set_ctl() and nfnetlink.c nfnetlink_rcv() enforce ns_capable/netlink_net_capable against the namespace user_ns.\nUI:N - The attacker installs the malformed CONNMARK rev2 rule and generates matching conntrack-associated traffic in their namespace; no separate victim action such as opening files, mounting media, or clicking links is required.\nS:U - Undefined shift during xt_CONNMARK packet targeting and resulting mark corruption remain within the host kernel security authority; this is standard local kernel netfilter compromise, not a VM escape, IOMMU bypass, or sandbox boundary crossing.\nC:L - Undefined-behavior shifts on 32-bit mark values produce attacker-influenced unpredictable ct-\u003emark and skb-\u003emark results observable through conntrack netlink and mark-based iptables/nftables matches, leaking altered connection-classification state within the namespace.\nI:H - Invalid shift_bits or shift_dir corrupt connmark_tg_shift() output written to nf_conn-\u003emark and skb-\u003emark, subverting mark-dependent firewall, policy-routing, QoS, and multi-tenant container egress controls on cloud routers and internet-facing servers.\nA:H - Evaluating a malformed CONNMARK rev2 rule with shift_bits\u003e=32 triggers C11 undefined-shift UB in connmark_tg_shift() during softirq netfilter processing; UBSAN-instrumented kernels panic on shift-out-of-bounds, and UB in the packet hot path can destabilize conntrack-driven forwarding."
            }
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      "providerMetadata": {
        "dateUpdated": "2026-08-17T05:43:05.530Z",
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        {
          "url": "https://git.kernel.org/stable/c/1b47026fb4b35bac850ad6e8a4ad7fc018e09ebc"
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      ],
      "title": "netfilter: xt_connmark: reject invalid shift parameters",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
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  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-72347",
    "datePublished": "2026-08-15T05:55:51.665Z",
    "dateReserved": "2026-08-09T03:40:39.920Z",
    "dateUpdated": "2026-08-17T05:43:05.530Z",
    "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-5J52-34GV-X96C

CVE-2026-72347 (GCVE-0-2026-72347)

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