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CVE-2026-80842ModerateLocalRevised 2 Oct

net: bridge: mcast: fix use-after-free of a master VLAN's multicast context

MSRC advisory NVD CVE.org

Assessment

Severity
Moderate
CVSS base score
5.7CVSS:3.1/AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:H/A:H
Impact
Not stated
EPSS · 30-day forecast
No EPSS score collected
Public detection template
No Nuclei template is listed in the current collected catalog
Exploitation detected
Unknown: not stated by MSRC
Exploitability
Not assessed
Publicly disclosed
Unknown: not stated by MSRC
Customer action
Required: follow the MSRC remediation guidance
Component
Mariner
Weakness
—
Issued by
Linux
Published
6 Sep 2026 · September 2026
Last revised
2 Oct 2026Information published.
CVSS 3.1 base metricsRed raises the risk · green lowers it
Attack vector
LocalAV:L
Attack complexity
HighAC:H
Privileges required
HighPR:H
User interaction
NoneUI:N
Scope
UnchangedS:U
Confidentiality
NoneC:N
Integrity
HighI:H
Availability
HighA:H

Updates that fix it

0 KBs

No KB listed

No KB update is listed in the collected MSRC record. Check the MSRC advisory for product releases and other remedies.

Affected products

Open Source Software
2 affected products
  • azl3 kernel 6.6.150.1-1 on Azure Linux 3.0
  • azl3 kernel 6.6.152.1-1 on Azure Linux 3.0

What changed

  1. Detection template: Unknown: detection-template evidence is incomplete or retained → No Nuclei template listed
  2. Detection template: No Nuclei template listed → Unknown: detection-template evidence is incomplete or retained
  3. Detection template: Unknown: detection-template evidence is incomplete or retained → No Nuclei template listed
  4. Detection template: No Nuclei template listed → Unknown: detection-template evidence is incomplete or retained
  5. Detection template: No Nuclei template listed · Customer action: Required: apply the update → Required: follow the MSRC remediation guidance · Public disclosure: No → Unknown: not stated by MSRC · Exploitation detected: Not reported by MSRC → Unknown: not stated by MSRC
  6. Detection template: Unknown: exploit-code evidence is incomplete or retained → No Nuclei template listed · CISA KEV: Unknown: catalog evidence is incomplete or retained → Not listed in the collected catalog
  7. Detection template: No Nuclei template listed → Unknown: exploit-code evidence is incomplete or retained · CISA KEV: Not listed in the collected catalog → Unknown: catalog evidence is incomplete or retained
Page history

Changes are dated when recorded; day views use the last saved version from that UTC day, and citations stay fixed.

Cite this version
Field-level log (35)

Up to 100 recent field edits are shown; older edits may be outside retention.

  1. 6 Nov 2026 · 17:32:22 UTC Public detection templateUnknown: detection-template evidence is incomplete or retained → No Nuclei template listed
  2. 6 Nov 2026 · 17:32:22 UTC Source coverage: public-exploit-codeIncomplete → Current
  3. 6 Nov 2026 · 17:32:22 UTC Source coverage: first-epssIncomplete → Current
  4. 6 Nov 2026 · 17:32:22 UTC Source coverage: msrc-cvrfIncomplete → Current
  5. 6 Nov 2026 · 16:31:02 UTC Public detection templateNo Nuclei template listed → Unknown: detection-template evidence is incomplete or retained
  6. 6 Nov 2026 · 16:31:02 UTC Source coverage: public-exploit-codeCurrent → Incomplete
  7. 6 Nov 2026 · 16:31:02 UTC Source coverage: first-epssCurrent → Incomplete
  8. 6 Nov 2026 · 16:31:02 UTC Source coverage: msrc-cvrfCurrent → Incomplete
  9. 2 Nov 2026 · 17:30:39 UTC Public detection templateUnknown: detection-template evidence is incomplete or retained → No Nuclei template listed
  10. 2 Nov 2026 · 17:30:39 UTC Source coverage: public-exploit-codeIncomplete → Current
  11. 2 Nov 2026 · 17:30:39 UTC Source coverage: first-epssIncomplete → Current
  12. 2 Nov 2026 · 17:30:39 UTC Source coverage: msrc-cvrfIncomplete → Current
  13. 2 Nov 2026 · 16:27:39 UTC Public detection templateNo Nuclei template listed → Unknown: detection-template evidence is incomplete or retained
  14. 2 Nov 2026 · 16:27:39 UTC Source coverage: public-exploit-codeCurrent → Incomplete
  15. 2 Nov 2026 · 16:27:39 UTC Source coverage: first-epssCurrent → Incomplete
  16. 2 Nov 2026 · 16:27:39 UTC Source coverage: msrc-cvrfCurrent → Incomplete
  17. 29 Oct 2026 · 20:19:26 UTC Public detection templateNo Nuclei template listed
  18. 29 Oct 2026 · 20:19:26 UTC EPSSNot scored → No EPSS score collected
  19. 29 Oct 2026 · 20:19:26 UTC Customer actionRequired: apply the update → Required: follow the MSRC remediation guidance
  20. 29 Oct 2026 · 20:19:26 UTC Publicly disclosedNo → Unknown: not stated by MSRC
  21. 29 Oct 2026 · 20:19:26 UTC Exploitation detectedNot reported by MSRC → Unknown: not stated by MSRC
  22. 23 Oct 2026 · 09:33:49 UTC Public exploit codeUnknown: exploit-code evidence is incomplete or retained → No Nuclei template listed
  23. 23 Oct 2026 · 09:33:49 UTC CISA KEVUnknown: catalog evidence is incomplete or retained → Not listed in the collected catalog
  24. 23 Oct 2026 · 09:33:49 UTC Source coverage: public-exploit-codeIncomplete → Current
  25. 23 Oct 2026 · 09:33:49 UTC Source coverage: first-epssIncomplete → Current
  26. 23 Oct 2026 · 09:33:49 UTC Source coverage: cisa-kevIncomplete → Current
  27. 23 Oct 2026 · 09:33:49 UTC Source coverage: msrc-cvrfIncomplete → Current
  28. 23 Oct 2026 · 08:31:50 UTC Public exploit codeNo Nuclei template listed → Unknown: exploit-code evidence is incomplete or retained
  29. 23 Oct 2026 · 08:31:50 UTC CISA KEVNot listed in the collected catalog → Unknown: catalog evidence is incomplete or retained
  30. 23 Oct 2026 · 08:31:50 UTC Source coverage: public-exploit-codeCurrent → Incomplete
  31. 23 Oct 2026 · 08:31:50 UTC Source coverage: first-epssCurrent → Incomplete
  32. 23 Oct 2026 · 08:31:50 UTC Source coverage: cisa-kevCurrent → Incomplete
  33. 23 Oct 2026 · 08:31:50 UTC Source coverage: msrc-cvrfCurrent → Incomplete
  34. 18 Oct 2026 · 14:54:30 UTC Link: September 2026/security?release=2026-Sep#cves
  35. 14 Oct 2026 · 11:22:42 UTC Source coverage: msrc-cvrfIncomplete → Current

Explore global source statements, affected packages and advisory history for CVE-2026-80842. The catalog has a separate collection scope from Microsoft release records.

Collected exploitation and prediction evidence

Risk source coverage

CISA KEV is observed exploitation evidence. FIRST EPSS is a dated prediction of exploitation in the next 30 days. Missing scores are unknown. This collector requests predictions only for explicit CVE aliases in the public NuGet archive; Microsoft release views retain their existing prediction scope.

No collected risk observation for these identifiers. This does not establish absence of exploitation or a zero probability.

cve-program · CVE-2026-80842

Published

net: bridge: mcast: fix use-after-free of a master VLAN's multicast context

In the Linux kernel, the following vulnerability has been resolved: net: bridge: mcast: fix use-after-free of a master VLAN's multicast context br_multicast_toggle_one_vlan() clears BR_VLFLAG_MCAST_ENABLED under br->multicast_lock before stopping a VLAN's multicast context. That is the teardown handshake: lockless readers gate on the flag through br_multicast_ctx_should_use() -> br_multicast_ctx_vlan_disabled(), so once it is cleared under the lock no reader can arm the context again. For a master VLAN the handshake never runs. __vlan_del() clears BRIDGE_VLAN_INFO_BRENTRY before calling br_vlan_put_master(), so br_multicast_toggle_one_vlan(masterv, false) returns early on !br_vlan_is_brentry(vlan): the flag stays set and br->multicast_lock is never taken. br_vlan_put_master() then drains the context in br_multicast_ctx_deinit() and frees the VLAN through call_rcu(), while a reader still inside rcu_read_lock() sees the context as enabled and re-arms it. The port and port-VLAN branch of the function has no br_vlan_is_brentry() test and flips the flag under br->multicast_lock, so it is not affected. The reader is the bridge transmit path. For a master VLAN br_multicast_rcv() selects brmctx = &vlan->br_mcast_ctx with pmctx = NULL, so IGMP sent to the bridge device re-arms the context's timers after br_multicast_ctx_deinit() has already stopped them. BUG: KASAN: slab-use-after-free in detach_if_pending+0x412/0x4a0 Write of size 8 at addr ffff88810ac39918 by task brmc/601 __mod_timer+0x51a/0xc50 br_multicast_host_join+0x25b/0x390 __br_multicast_add_group+0x468/0x530 br_ip4_multicast_add_group+0x1a0/0x260 br_multicast_rcv+0x2cda/0x61e0 br_dev_xmit+0x6c4/0x1540 Allocated by task 610: br_vlan_add+0x111/0xb40 br_vlan_info+0x370/0x3e0 Freed by task 0: kfree+0x1a7/0x4f0 rcu_core+0x7dc/0x10a0 Only test br_vlan_is_brentry() when enabling, like the br_multicast_ctx_vlan_global_disabled() test next to it. Disabling then always clears BR_VLFLAG_MCAST_ENABLED under br->multicast_lock before br_multicast_ctx_deinit() drains the context.

Source published
4 Sep 2026 15:54:52 UTC
Source modified
19 Oct 2026 08:44:35 UTC
Observed here
23 Oct 2026 15:48:27 UTC
Source terms
CVE Program Terms of Use

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