# CVE-2026-100081: xen-netback: defer xenvif_mcast_addr_list_free()

Status: published. Published: 2026-11-06. Updated: 2026-11-10.

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

xen-netback: defer xenvif_mcast_addr_list_free()

In order for the function to legitimately avoid locking/RCU, it needs to
run after all TX/RX processing has finished/stopped: Lookups happen from
xenvif_start_xmit(), while adds/removes happen from xenvif_tx_action()
(called out of xenvif_poll()).

Move the call out of xenvif_disconnect_data() (the call to the function
from connect()'s error path doesn't require any cleaning up there), and
put it past the synchronization point in backend_disconnect().

This is XSA-527 / CVE-2026-100081.

## Remediation

No remediation reported in collected sources

## Affected products and versions

- Linux / Linux: ≥ b17075d5c1988b83f840d272c795ac17d57ce804; < 96e05a8ce243e2207704e2e7a6e7d1172730f515 (affected, git); ≥ b17075d5c1988b83f840d272c795ac17d57ce804; < 0e786123e46d08d2247ce93a5435e45ed9f4c5d1 (affected, git); ≥ b17075d5c1988b83f840d272c795ac17d57ce804; < 990d123d9eaa3ac6c979eed245658676d65ce0db (affected, git); ≥ b17075d5c1988b83f840d272c795ac17d57ce804; < 0d515c409033c8e2a645a781be3ca76ab825fc8c (affected, git); ≥ b17075d5c1988b83f840d272c795ac17d57ce804; < a6bb2f1fa62c56279bdcdadce28d1310c5e12b62 (affected, git); ≥ b17075d5c1988b83f840d272c795ac17d57ce804; < 34f0f63dc6dc11895a17bb5672451b6b11622c99 (affected, git); ≥ b17075d5c1988b83f840d272c795ac17d57ce804; < fb38fc58acb26d74fe8f7b19621fafaae3c040ff (affected, git). Source: CNA: Linux
- Linux / Linux: 4.11 (affected); ≥ 0; < 4.11 (unaffected, semver); ≥ 5.10.274; ≤ 5.10.* (unaffected, semver); ≥ 5.15.225; ≤ 5.15.* (unaffected, semver); ≥ 6.1.192; ≤ 6.1.* (unaffected, semver); ≥ 6.6.162; ≤ 6.6.* (unaffected, semver); ≥ 6.12.116; ≤ 6.12.* (unaffected, semver); ≥ 6.18.62; ≤ 6.18.* (unaffected, semver); ≥ 7.3.3; ≤ 7.3.* (unaffected, semver). Source: CNA: Linux

## Severity and prioritization

- CVSS 3.1: 7.8 (high); CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:C/C:H/I:H/A:H; source: CNA: Linux

- CVSS 3.1: 7.8 (high); CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:C/C:H/I:H/A:H; source: NVD: 416baaa9-dc9f-4396-8d5f-8c081fb06d67

- CISA KEV: No listing in collected sources

- EPSS: 0.24% as of 2026-11-10; percentile 15.72%

- SSVC: Not available

- Weaknesses: Not reported

## Exploit evidence

No exploit evidence in collected sources. This is not proof of no exploitation.

## References

- https://git.kernel.org/stable/c/96e05a8ce243e2207704e2e7a6e7d1172730f515 (CNA: Linux)

- https://git.kernel.org/stable/c/0e786123e46d08d2247ce93a5435e45ed9f4c5d1 (CNA: Linux)

- https://git.kernel.org/stable/c/990d123d9eaa3ac6c979eed245658676d65ce0db (CNA: Linux)

- https://git.kernel.org/stable/c/0d515c409033c8e2a645a781be3ca76ab825fc8c (CNA: Linux)

- https://git.kernel.org/stable/c/a6bb2f1fa62c56279bdcdadce28d1310c5e12b62 (CNA: Linux)

- https://git.kernel.org/stable/c/34f0f63dc6dc11895a17bb5672451b6b11622c99 (CNA: Linux)

- https://git.kernel.org/stable/c/fb38fc58acb26d74fe8f7b19621fafaae3c040ff (CNA: Linux)

- http://www.openwall.com/lists/oss-security/2026/11/06/10 (ADP: CVE)

- http://xenbits.xen.org/xsa/advisory-527.html (ADP: CVE)

- https://git.kernel.org/stable/c/0d515c409033c8e2a645a781be3ca76ab825fc8c (416baaa9-dc9f-4396-8d5f-8c081fb06d67)

- https://git.kernel.org/stable/c/0e786123e46d08d2247ce93a5435e45ed9f4c5d1 (416baaa9-dc9f-4396-8d5f-8c081fb06d67)

- https://git.kernel.org/stable/c/34f0f63dc6dc11895a17bb5672451b6b11622c99 (416baaa9-dc9f-4396-8d5f-8c081fb06d67)

- https://git.kernel.org/stable/c/96e05a8ce243e2207704e2e7a6e7d1172730f515 (416baaa9-dc9f-4396-8d5f-8c081fb06d67)

- https://git.kernel.org/stable/c/990d123d9eaa3ac6c979eed245658676d65ce0db (416baaa9-dc9f-4396-8d5f-8c081fb06d67)

- https://git.kernel.org/stable/c/a6bb2f1fa62c56279bdcdadce28d1310c5e12b62 (416baaa9-dc9f-4396-8d5f-8c081fb06d67)

- https://git.kernel.org/stable/c/fb38fc58acb26d74fe8f7b19621fafaae3c040ff (416baaa9-dc9f-4396-8d5f-8c081fb06d67)

- http://www.openwall.com/lists/oss-security/2026/11/06/10 (af854a3a-2127-422b-91ae-364da2661108)

- http://xenbits.xen.org/xsa/advisory-527.html (af854a3a-2127-422b-91ae-364da2661108)

## Provenance

- CNA: Linux: https://www.cve.org/CVERecord?id=CVE-2026-100081; retrieved 2026-11-10; source updated 2026-11-10

- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-100081; retrieved 2026-11-10; source updated 2026-11-10

- FIRST EPSS: https://api.first.org/data/v1/epss?cve=CVE-2026-100081; retrieved 2026-11-10; source updated Not reported

Revision: c83299cdcbc194ba3b4b2ff343c168b1b680d7bb82c6b54d467daf1eeaa8c411

Canonical: https://y2.dev/cve/CVE-2026-100081

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