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

Vulnerability from cvelistv5 – Published: 2026-08-15 05:55 – Updated: 2026-08-17 05:43
VLAI
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
References
Impacted products
Vendor Product Version CPE status
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)
guessed Create a notification for this product.
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)
guessed Create a notification for this product.
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{
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          "programFiles": [
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              "version": "6.12.97",
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          "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."
        }
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            "baseSeverity": "HIGH",
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              "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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    "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",
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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.\"}],\"affected\":[{\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"affectedData\":[{\"vendor\":\"Linux\",\"product\":\"Linux\",\"defaultStatus\":\"unaffected\",\"programFiles\":[\"net/netfilter/xt_connmark.c\"],\"repo\":\"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\"versions\":[{\"version\":\"472a73e00757b971d613d796374d2727b2e4954d\",\"lessThan\":\"d8ce63d928b457fba7ed1e302492dfd32293671c\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"472a73e00757b971d613d796374d2727b2e4954d\",\"lessThan\":\"9657bb11a6376ab0a79f05d433713d6944111e9d\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"472a73e00757b971d613d796374d2727b2e4954d\",\"lessThan\":\"8ace320ac4416f5e5fbcd065309fb2dfcce787b0\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"472a73e00757b971d613d796374d2727b2e4954d\",\"lessThan\":\"c3fa852d117b3fda72265e4230e3967db4a74fcf\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"472a73e00757b971d613d796374d2727b2e4954d\",\"lessThan\":\"4eef84b09a3836919360c4232b0f16651a155eec\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"472a73e00757b971d613d796374d2727b2e4954d\",\"lessThan\":\"230173cc6105bdfb2696d37e6e56687b003fbe63\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"472a73e00757b971d613d796374d2727b2e4954d\",\"lessThan\":\"1b47026fb4b35bac850ad6e8a4ad7fc018e09ebc\",\"versionType\":\"git\",\"status\":\"affected\"}]},{\"vendor\":\"Linux\",\"product\":\"Linux\",\"defaultStatus\":\"affected\",\"programFiles\":[\"net/netfilter/xt_connmark.c\"],\"repo\":\"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\"versions\":[{\"version\":\"4.17\",\"status\":\"affected\"},{\"version\":\"0\",\"lessThan\":\"4.17\",\"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:L/I:H/A:H\",\"baseScore\":7.3,\"baseSeverity\":\"HIGH\",\"attackVector\":\"LOCAL\",\"attackComplexity\":\"LOW\",\"privilegesRequired\":\"LOW\",\"userInteraction\":\"NONE\",\"scope\":\"UNCHANGED\",\"confidentialityImpact\":\"LOW\",\"integrityImpact\":\"HIGH\",\"availabilityImpact\":\"HIGH\"},\"exploitabilityScore\":1.8,\"impactScore\":5.5}]},\"references\":[{\"url\":\"https://git.kernel.org/stable/c/1b47026fb4b35bac850ad6e8a4ad7fc018e09ebc\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/230173cc6105bdfb2696d37e6e56687b003fbe63\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/4eef84b09a3836919360c4232b0f16651a155eec\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/8ace320ac4416f5e5fbcd065309fb2dfcce787b0\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/9657bb11a6376ab0a79f05d433713d6944111e9d\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/c3fa852d117b3fda72265e4230e3967db4a74fcf\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/d8ce63d928b457fba7ed1e302492dfd32293671c\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"}]}}",
    "redhat_vex": {
      "aggregate_severity": "Low",
      "current_release_date": "2026-08-19T17:51:10+00:00",
      "cve": "CVE-2026-72347",
      "id": "CVE-2026-72347",
      "initial_release_date": "2026-08-15T00:00:00+00:00",
      "product_status:known_affected": "246",
      "product_status:known_not_affected": "28",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: netfilter: xt_connmark: reject invalid shift parameters",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-72347.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.

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.