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_SFBLOCK macro.

Project Subscriptions

Vendors Products
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Advisories
Source ID Title
Debian DLA Debian DLA DLA-4850-1 linux-6.12 security update
Debian DSA Debian DSA DSA-6568-1 linux security update
Fixes

Solution

No solution given by the vendor.


Workaround

No workaround given by the vendor.

History

Wed, 07 Oct 2026 10:00:00 +0000

Type Values Removed Values Added
Weaknesses CWE-362

Tue, 06 Oct 2026 12:15:00 +0000

Type Values Removed Values Added
Weaknesses CWE-366
References
Metrics threat_severity

None

cvssV3_1

{'score': 4.4, 'vector': 'CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N'}

threat_severity

Low


Sat, 03 Oct 2026 11:15:00 +0000


Fri, 25 Sep 2026 12:15:00 +0000

Type Values Removed Values Added
Weaknesses CWE-362

Fri, 25 Sep 2026 10:45:00 +0000

Type Values Removed Values Added
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_SFBLOCK macro.
Title ipv6: mcast: use copy-on-write RCU updates in ip6_mc_source()
First Time appeared Linux
Linux linux Kernel
CPEs cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
Vendors & Products Linux
Linux linux Kernel
References

Projects

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cve-icon MITRE

Status: PUBLISHED

Assigner: Linux

Published:

Updated: 2026-10-19T09:13:53.770Z

Reserved: 2026-09-25T10:25:14.315Z

Link: CVE-2026-98101

cve-icon Vulnrichment

No data.

cve-icon NVD

Status : Undergoing Analysis

Published: 2026-09-25T11:17:39.830

Modified: 2026-10-19T10:18:07.260

Link: CVE-2026-98101

cve-icon Redhat

Severity : Low

Publid Date: 2026-09-25T00:00:00Z

Links: CVE-2026-98101 - Bugzilla

cve-icon OpenCVE Enrichment

Updated: 2026-10-07T11:45:16Z

Weaknesses