Linux Kernel up to 7.2.6/7.3-rc1 IPv6 Multicast net/ipv6/mcast.c ipv6_mc_list/mc_list/mc_tomb race condition

Summaryinfo

A vulnerability categorized as very critical has been discovered in Linux Kernel up to 7.2.6/7.3-rc1. The affected element is the function __ipv6_dev_mc_dec/ipv6_sock_mc_drop/__ipv6_sock_mc_close/__ipv6_sock_mc_join/mld_del_delrec/__ipv6_dev_mc_inc of the file net/ipv6/mcast.c of the component IPv6 Multicast. Such manipulation of the argument ipv6_mc_list/mc_list/mc_tomb leads to race condition. This vulnerability is documented as CVE-2026-98099. The attack can be executed remotely. There is not any exploit available. It is advisable to upgrade the affected component.

Detailsinfo

A vulnerability was found in Linux Kernel up to 7.2.6/7.3-rc1 and classified as very critical. Affected by this issue is the function __ipv6_dev_mc_dec/ipv6_sock_mc_drop/__ipv6_sock_mc_close/__ipv6_sock_mc_join/mld_del_delrec/__ipv6_dev_mc_inc of the file net/ipv6/mcast.c of the component IPv6 Multicast. The manipulation of the argument ipv6_mc_list/mc_list/mc_tomb with an unknown input leads to a race condition vulnerability. Using CWE to declare the problem leads to CWE-362. The product contains a code sequence that can run concurrently with other code, and the code sequence requires temporary, exclusive access to a shared resource, but a timing window exists in which the shared resource can be modified by another code sequence that is operating concurrently. Impacted is confidentiality, integrity, and availability. CVE summarizes:

In the Linux kernel, the following vulnerability has been resolved: ipv6: mcast: use rcu_assign_pointer() for __rcu list updates Several places in net/ipv6/mcast.c update RCU-protected lists (np->ipv6_mc_list, idev->mc_list, idev->mc_tomb) using direct pointer assignments instead of rcu_assign_pointer(): 1. In __ipv6_dev_mc_dec(), unlinking a group from idev->mc_list did: *map = ma->next; without rcu_assign_pointer() while concurrent readers traverse idev->mc_list locklessly under rcu_read_lock(). 2. In ipv6_sock_mc_drop() and __ipv6_sock_mc_close(), unlinking a group from np->ipv6_mc_list directly assigned *lnk = mc_lst->next and np->ipv6_mc_list = mc_lst->next without rcu_assign_pointer(), racing with lockless readers in inet6_mc_check(). 3. In __ipv6_sock_mc_join(), mc_lst->next was initialized to np->ipv6_mc_list via raw assignment before publishing mc_lst. 4. In mld_del_delrec() and __ipv6_dev_mc_inc(), __rcu source pointers passed into rcu_assign_pointer() lacked explicit dereference helpers. Fix these by consistently using rcu_assign_pointer() along with mc_dereference() / sock_dereference().

The advisory is available at git.kernel.org. This vulnerability is handled as CVE-2026-98099 since 09/25/2026. The exploitation is known to be easy. The attack may be launched remotely. No form of authentication is required for exploitation. Technical details are known, but there is no available exploit. The structure of the vulnerability defines a possible price range of USD $0-$5k at the moment (estimation calculated on 09/25/2026).

Upgrading to version 7.2.7 or 7.3-rc2 eliminates this vulnerability. Applying the patch 2e46b0c9fcf7e10b64ce1630b925f47918d1f7f6/0c8f56c583c3250408367880c98e4d6fbc929315 is able to eliminate this problem. The best possible mitigation is suggested to be upgrading to the latest version.

If you want to get best quality of vulnerability data, you may have to visit VulDB.

Productinfo

Type

• Operating System

Vendor

• Linux

Name

• Kernel

Version

• 7.2.0
• 7.2.1
• 7.2.2
• 7.2.3
• 7.2.4
• 7.2.5
• 7.2.6
• 7.3-rc1

License

• open-source

Website

• Vendor: https://www.kernel.org/

CPE 2.3info

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CPE 2.2info

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