CVE-2026-72347 (GCVE-0-2026-72347)
Vulnerability from cvelistv5
Published
2026-08-15 05:55
Modified
2026-08-17 05:43
Severity ?
VLAI Severity ?
EPSS score ?
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.
References
Impacted products
| Vendor | Product | Version | ||
|---|---|---|---|---|
| Linux | Linux |
Version: 472a73e00757b971d613d796374d2727b2e4954d Version: 472a73e00757b971d613d796374d2727b2e4954d Version: 472a73e00757b971d613d796374d2727b2e4954d Version: 472a73e00757b971d613d796374d2727b2e4954d Version: 472a73e00757b971d613d796374d2727b2e4954d Version: 472a73e00757b971d613d796374d2727b2e4954d Version: 472a73e00757b971d613d796374d2727b2e4954d |
||
{
"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": [
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"status": "affected",
"version": "472a73e00757b971d613d796374d2727b2e4954d",
"versionType": "git"
},
{
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"status": "affected",
"version": "472a73e00757b971d613d796374d2727b2e4954d",
"versionType": "git"
},
{
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"status": "affected",
"version": "472a73e00757b971d613d796374d2727b2e4954d",
"versionType": "git"
},
{
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"status": "affected",
"version": "472a73e00757b971d613d796374d2727b2e4954d",
"versionType": "git"
},
{
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"status": "affected",
"version": "472a73e00757b971d613d796374d2727b2e4954d",
"versionType": "git"
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{
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"status": "affected",
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{
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"status": "affected",
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"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": [
{
"nodes": [
{
"cpeMatch": [
{
"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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"versionStartIncluding": "4.17",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "6.12.97",
"versionStartIncluding": "4.17",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "6.18.40",
"versionStartIncluding": "4.17",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "7.1.5",
"versionStartIncluding": "4.17",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "7.2",
"versionStartIncluding": "4.17",
"vulnerable": true
}
],
"negate": false,
"operator": "OR"
}
]
}
],
"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."
}
]
}
],
"providerMetadata": {
"dateUpdated": "2026-08-17T05:43:05.530Z",
"orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"shortName": "Linux"
},
"references": [
{
"url": "https://git.kernel.org/stable/c/d8ce63d928b457fba7ed1e302492dfd32293671c"
},
{
"url": "https://git.kernel.org/stable/c/9657bb11a6376ab0a79f05d433713d6944111e9d"
},
{
"url": "https://git.kernel.org/stable/c/8ace320ac4416f5e5fbcd065309fb2dfcce787b0"
},
{
"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",
"x_generator": {
"engine": "bippy-1.2.0"
}
}
},
"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"
}
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Sightings
| Author | Source | Type | Date |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or seen somewhere by the user.
- Confirmed: The vulnerability is confirmed from an analyst perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: This vulnerability was exploited and seen by the user reporting the sighting.
- Patched: This vulnerability was successfully patched by the user reporting the sighting.
- Not exploited: This vulnerability was not exploited or seen by the user reporting the sighting.
- Not confirmed: The user expresses doubt about the veracity of the vulnerability.
- Not patched: This vulnerability was not successfully patched by the user reporting the sighting.
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