GHSA-9GQ3-J787-CJHR
Vulnerability from github – Published: 2026-08-10 15:33 – Updated: 2026-08-19 18:32In the Linux kernel, the following vulnerability has been resolved:
amt: re-read skb header pointers after every pull
Several AMT receive and transmit paths cache a pointer into the skb head (ip_hdr(), ipv6_hdr(), eth_hdr() or the AMT message header) and then call a helper that can reallocate that head before the cached pointer is used again. pskb_may_pull(), ip_mc_may_pull(), ipv6_mc_may_pull(), iptunnel_pull_header(), ip_mc_check_igmp() and ipv6_mc_check_mld() can all free the old head and move the data, so a pointer taken before the call dangles afterwards and the later access is a use-after-free of the freed head.
The affected sites are:
amt_rcv() caches ip_hdr() before amt_parse_type() pulls, then reads iph->saddr.
amt_dev_xmit() caches ip_hdr()/ipv6_hdr() before ip_mc_check_igmp()/ ipv6_mc_check_mld() and pskb_may_pull(), then reads the group address.
amt_multicast_data_handler() caches eth_hdr() before pskb_may_pull(), then writes the L2 header.
amt_membership_query_handler() caches the AMT header, the outer and inner eth_hdr() and ip_hdr() before iptunnel_pull_header() and several pulls, then reads and writes them.
amt_igmpv3_report_handler() and amt_mldv2_report_handler() cache ip_hdr()/ipv6_hdr() and the current group record and read the record count from the report header inside the record loop, across the *_mc_may_pull() calls.
amt_update_handler() caches ip_hdr() and the AMT membership-update header before pskb_may_pull(), iptunnel_pull_header(), ip_mc_check_igmp() and the report handler, then reads iph->daddr and amtmu->nonce / amtmu->response_mac.
Fix each site by either snapshotting the scalar that is used after the pull before the first pull runs, or re-deriving the header pointer from the skb after the last pull that can move the head. Values that are stable across the pull (source and group address, the response MAC and nonce, the record count, the outer source MAC) are snapshotted; pointers that are written through or read repeatedly are re-derived.
{
"affected": [],
"aliases": [
"CVE-2026-68302"
],
"database_specific": {
"cwe_ids": [],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2026-08-10T13:20:19Z",
"severity": "CRITICAL"
},
"details": "In the Linux kernel, the following vulnerability has been resolved:\n\namt: re-read skb header pointers after every pull\n\nSeveral AMT receive and transmit paths cache a pointer into the skb head\n(ip_hdr(), ipv6_hdr(), eth_hdr() or the AMT message header) and then call\na helper that can reallocate that head before the cached pointer is used\nagain. pskb_may_pull(), ip_mc_may_pull(), ipv6_mc_may_pull(),\niptunnel_pull_header(), ip_mc_check_igmp() and ipv6_mc_check_mld() can all\nfree the old head and move the data, so a pointer taken before the call\ndangles afterwards and the later access is a use-after-free of the freed\nhead.\n\nThe affected sites are:\n\n amt_rcv() caches ip_hdr() before amt_parse_type() pulls, then reads\n iph-\u003esaddr.\n\n amt_dev_xmit() caches ip_hdr()/ipv6_hdr() before ip_mc_check_igmp()/\n ipv6_mc_check_mld() and pskb_may_pull(), then reads the group address.\n\n amt_multicast_data_handler() caches eth_hdr() before pskb_may_pull(),\n then writes the L2 header.\n\n amt_membership_query_handler() caches the AMT header, the outer and\n inner eth_hdr() and ip_hdr() before iptunnel_pull_header() and several\n pulls, then reads and writes them.\n\n amt_igmpv3_report_handler() and amt_mldv2_report_handler() cache\n ip_hdr()/ipv6_hdr() and the current group record and read the record\n count from the report header inside the record loop, across the\n *_mc_may_pull() calls.\n\n amt_update_handler() caches ip_hdr() and the AMT membership-update\n header before pskb_may_pull(), iptunnel_pull_header(),\n ip_mc_check_igmp() and the report handler, then reads iph-\u003edaddr and\n amtmu-\u003enonce / amtmu-\u003eresponse_mac.\n\nFix each site by either snapshotting the scalar that is used after the\npull before the first pull runs, or re-deriving the header pointer from\nthe skb after the last pull that can move the head. Values that are\nstable across the pull (source and group address, the response MAC and\nnonce, the record count, the outer source MAC) are snapshotted; pointers\nthat are written through or read repeatedly are re-derived.",
"id": "GHSA-9gq3-j787-cjhr",
"modified": "2026-08-19T18:32:13Z",
"published": "2026-08-10T15:33:45Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-68302"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/3656a79f94c471827a08f2cacce5f94ad5e52c24"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/37ff890f9c18dfbcf57e17199901d4fd1e4c174e"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/7746d588d42a4ac0117b68ed8e9b22a9da53dfb7"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/7f48e3ddad8e97545b25788b8203b3a539df1621"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/9005b221cb1f9c3c1a2ef656fb0e8fa80c0a187e"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/ca0e8b661957f777591efe874cd9d9a63619cd99"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
"type": "CVSS_V3"
}
]
}
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.
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- Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
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- 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 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.