{"id":"CVE-2026-98101","title":"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 U…","summary":"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 U…","severity":"medium","vendor":"Linux","product":"Linux","affected":["Linux >= 882ba1f73c06831f2a21044ebd8864c485ac04f2 < ac51321d3b2391860a935820ebcf4d8b9bb16a8a","Linux >= 882ba1f73c06831f2a21044ebd8864c485ac04f2 < dba00514bf668c26cb4900e9f0da84bf96bf065a","Linux >= 882ba1f73c06831f2a21044ebd8864c485ac04f2 < 2c2091e2ee93049fc513ad1e6c99d8b6c809f467","Linux >= 882ba1f73c06831f2a21044ebd8864c485ac04f2 < 20db91a052332ef5552bd2f651ffb9db911cf67b","Linux >= 882ba1f73c06831f2a21044ebd8864c485ac04f2 < c073d1b070f171d206b19c98d71739a97f15b3f1","Linux 47c75e3923c8d562fea8daf0ccf31546a7bef0ea","Linux >= 5.10.261 < 5.11","Linux 5.13"],"published":"2026-09-25","updated":"2026-10-03","sourceUpdated":"2026-10-03T11:18:32.250","source":"NVD","sourceUrl":"https://nvd.nist.gov/vuln/detail/CVE-2026-98101","references":[{"url":"https://git.kernel.org/stable/c/20db91a052332ef5552bd2f651ffb9db911cf67b","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/2c2091e2ee93049fc513ad1e6c99d8b6c809f467","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/ac51321d3b2391860a935820ebcf4d8b9bb16a8a","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/c073d1b070f171d206b19c98d71739a97f15b3f1","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/dba00514bf668c26cb4900e9f0da84bf96bf065a","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-98101.json"},{"url":"https://access.redhat.com/security/cve/CVE-2026-98101"},{"url":"https://bugzilla.redhat.com/show_bug.cgi?id=2541378"},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-98101"},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-98101"},{"url":"https://git.kernel.org/pub/scm/linux/security/vulns.git/plain/cve/published/2026/CVE-2026-98101.mbox"}],"tags":["nvd","cve.org","csaf","vex","red-hat"],"epss":0.00168,"epssPercentile":0.06032,"ingestedAt":"2026-09-25T11:06:38.827Z","cvss":4.4,"cvssVector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N","cvssSource":"vendor","cwe":["CWE-366"],"slug":"CVE-2026-98101","body":"## Overview\n\nIn 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.\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.\n\n## Vendor advisories\n\n- **Red Hat VEX** · Low · affected: Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 6, Red Hat Enterprise Linux 9, Red Hat OpenShift Container Platform 4 · no fix planned: Red Hat Enterprise Linux 6, Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 9, Red Hat OpenShift Container Platform 4 · updated 2026-10-05 · [vex](https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-98101.json)","depth":"sunlit","depthScore":24,"depthScoreParts":{"impact":24.2,"likelihood":0,"exploitation":0,"ransomware":0},"changes":[{"seq":216328,"id":"CVE-2026-98101","ts":1791274074083,"field":"cvss","old":null,"new":"4.4"},{"seq":216327,"id":"CVE-2026-98101","ts":1791274074083,"field":"severity","old":"none","new":"medium"}]}