{"id":"CVE-2026-98101","published":"2026-09-25T11:17:39.830","lastModified":"2026-09-25T11:17:39.830","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nipv6: mcast: use copy-on-write RCU updates in ip6_mc_source()\n\npmc->sflist is read locklessly under rcu_read_lock() by\ninet6_mc_check() during packet reception in the UDP and RAW\nmulticast receive paths.\n\nip6_mc_source() mutated psl->sl_addr and psl->sl_count in-place\nwhen adding or removing a source filter. Additionally, when expanding\nthe filter buffer, newpsl was published via rcu_assign_pointer()\nbefore writing the new source into the array.\n\nBecause 16-byte struct in6_addr writes are not atomic and array\nshifting is not synchronized with RCU readers, concurrent readers in\ninet6_mc_check() could read torn IPv6 addresses or observe\nduplicated/missed source entries.\n\nFix this by switching ip6_mc_source() to copy-on-write RCU updates:\nallocate and fully populate newpsl before publishing it via\nrcu_assign_pointer(), and reclaim the old filter via kfree_rcu(),\nmatching ip6_mc_msfilter().\n\nAlso remove the now unused IP6_SFBLOCK macro.","cvssScore":null,"cvssSeverity":null,"cvssVector":null,"cwes":[],"vendors":[],"products":[],"references":[{"url":"https://git.kernel.org/stable/c/20db91a052332ef5552bd2f651ffb9db911cf67b","tags":[]},{"url":"https://git.kernel.org/stable/c/2c2091e2ee93049fc513ad1e6c99d8b6c809f467","tags":[]},{"url":"https://git.kernel.org/stable/c/c073d1b070f171d206b19c98d71739a97f15b3f1","tags":[]}],"exploitRefs":[],"hasPoc":false,"ai":null}