CVE-2026-98101

/// Technical description

In the Linux kernel, the following vulnerability has been resolved:

ipv6: mcast: use copy-on-write RCU updates in ip6_mc_source()

pmc->sflist is read locklessly under rcu_read_lock() by

inet6_mc_check() during packet reception in the UDP and RAW

multicast receive paths.

ip6_mc_source() mutated psl->sl_addr and psl->sl_count in-place

when adding or removing a source filter. Additionally, when expanding

the filter buffer, newpsl was published via rcu_assign_pointer()

before writing the new source into the array.

Because 16-byte struct in6_addr writes are not atomic and array

shifting is not synchronized with RCU readers, concurrent readers in

inet6_mc_check() could read torn IPv6 addresses or observe

duplicated/missed source entries.

Fix this by switching ip6_mc_source() to copy-on-write RCU updates:

allocate and fully populate newpsl before publishing it via

rcu_assign_pointer(), and reclaim the old filter via kfree_rcu(),

matching ip6_mc_msfilter().

Also remove the now unused IP6

/// Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

/// References