CVE-2026-72347 (GCVE-0-2026-72347)
Vulnerability from cvelistv5 – Published: 2026-08-15 05:55 – Updated: 2026-08-17 05:43
VLAI
EPSS
VEX
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)
Assigner
References
7 references
Impacted products
2 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 | |
| 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 |
{
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"programFiles": [
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"version": "6.6.145",
"versionType": "semver"
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"version": "6.12.97",
"versionType": "semver"
},
{
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"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": [
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],
"descriptions": [
{
"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",
"orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"shortName": "Linux"
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"url": "https://git.kernel.org/stable/c/d8ce63d928b457fba7ed1e302492dfd32293671c"
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"url": "https://git.kernel.org/stable/c/9657bb11a6376ab0a79f05d433713d6944111e9d"
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{
"url": "https://git.kernel.org/stable/c/c3fa852d117b3fda72265e4230e3967db4a74fcf"
},
{
"url": "https://git.kernel.org/stable/c/4eef84b09a3836919360c4232b0f16651a155eec"
},
{
"url": "https://git.kernel.org/stable/c/230173cc6105bdfb2696d37e6e56687b003fbe63"
},
{
"url": "https://git.kernel.org/stable/c/1b47026fb4b35bac850ad6e8a4ad7fc018e09ebc"
}
],
"title": "netfilter: xt_connmark: reject invalid shift parameters",
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"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"
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"date": "2026-10-03",
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"percentile": "0.06157"
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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."
}
],
"id": "CVE-2026-72347",
"lastModified": "2026-08-17T06:18:38.643",
"metrics": {
"cvssMetricV31": [
{
"cvssData": {
"attackComplexity": "LOW",
"attackVector": "LOCAL",
"availabilityImpact": "HIGH",
"baseScore": 7.3,
"baseSeverity": "HIGH",
"confidentialityImpact": "LOW",
"integrityImpact": "HIGH",
"privilegesRequired": "LOW",
"scope": "UNCHANGED",
"userInteraction": "NONE",
"vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:L/I:H/A:H",
"version": "3.1"
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"impactScore": 5.5,
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"type": "Secondary"
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"published": "2026-08-15T06:22:08.070",
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"sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"vulnStatus": "Received"
}
},
"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"
},
"suse_vex": {
"aggregate_severity": "moderate",
"current_release_date": "2026-10-03T00:28:25Z",
"cve": "CVE-2026-72347",
"id": "CVE-2026-72347",
"initial_release_date": "2026-09-01T13:29:44Z",
"product_status:known_affected": "271",
"product_status:known_not_affected": "93",
"product_status:recommended": "145",
"source": "SUSE CSAF VEX",
"status": "interim",
"title": "SUSE CVE CVE-2026-72347",
"url": "https://ftp.suse.com/pub/projects/security/csaf-vex/cve-2026-72347.json",
"version": "6"
}
}
}
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Experimental. This forecast is provided for visualization only and may change without notice. Do not use it for operational decisions.
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.
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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.
Browse all ATT&CK techniques and the vulnerabilities related to each.
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.
Browse all ATT&CK techniques and the vulnerabilities related to each.
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Related by attack behaviour
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