CVE-2026-68302 amt: re-read skb header pointers after every pull
A use-after-free vulnerability in the Linux kernel's Automatic Multicast Tunneling module allows attackers to cause denial of service or execute arbitrary code.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-68302?
CVE-2026-68302 is a critical use after free vulnerability in Linux, published on 10 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
In 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.
Which versions are affected by CVE-2026-68302?
How do I fix CVE-2026-68302?
Apply the vendor's patch.
Upgrade to the fixed version. These bugs are found with fuzzing and sanitisers and avoided by memory-safe languages. More about Use after free.
Is CVE-2026-68302 being exploited?
There is no known exploitation of CVE-2026-68302 in the wild and no public exploit code.
Sources
Also known as BELL-CVE-2026-68302, DEBIAN-CVE-2026-68302, GHSA-9gq3-j787-cjhr, UBUNTU-CVE-2026-68302.