{"answers":{"affected":"","exploited":"There is no known exploitation of CVE-2026-80842 in the wild and no public exploit code.","fix":"Apply the vendor's patch.","what":"CVE-2026-80842 is an use after free vulnerability in Linux, published on 4 Sep 2026. It can only be exploited from the same machine or local network, with no action from the victim."},"fix_prompt":"Check this codebase for CVE-2026-80842 and fix it if it is affected.\n\nWhat it is: CVE-2026-80842 is an use after free vulnerability in Linux, published on 4 Sep 2026. It can only be exploited from the same machine or local network, with no action from the victim.\nExploitation: There is no known exploitation of CVE-2026-80842 in the wild and no public exploit code.\n\nAffected product: Linux. No package-level version data is available, so check the vendor advisory linked from the reference page.\n\nTask:\n1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.\n2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.\n3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.\n4. Run the tests and summarise what changed and why.\n5. If nothing in the project is affected, say so and change nothing.\n\nReference: https://insights.sbomify.com/CVE-2026-80842/ (Markdown: https://insights.sbomify.com/CVE-2026-80842/index.md)","id":"CVE-2026-80842","markdown":"https://insights.sbomify.com/CVE-2026-80842/index.md","name":"CVE-2026-80842","record":{"aliases":["AZL-99528","BELL-CVE-2026-80842","DEBIAN-CVE-2026-80842","GHSA-4rr3-fvjp-hj2g","UBUNTU-CVE-2026-80842"],"analysis":{"component_type":"kernel","fix_type":"patch","impacts":["code_execution","denial_of_service"],"network_reachable":"adjacent_or_local","non_default_config":true,"product_category":"Linux kernel bridge","requires_auth":"low_privilege","summary":"A use-after-free in the Linux kernel bridge multicast code allows local attackers to cause denial of service or execute arbitrary code.","user_interaction":"not_required","vuln_class":"use_after_free"},"analysis_generated_by":"qwen3.8-flash-next","assigner":"Linux","cpe":[],"cvss":{"score":null,"severity":null,"source":null,"vector":null,"version":null},"cwes":[],"description":"In the Linux kernel, the following vulnerability has been resolved:\n\nnet: bridge: mcast: fix use-after-free of a master VLAN's multicast context\n\nbr_multicast_toggle_one_vlan() clears BR_VLFLAG_MCAST_ENABLED under\nbr-\u003emulticast_lock before stopping a VLAN's multicast context.  That is\nthe teardown handshake: lockless readers gate on the flag through\nbr_multicast_ctx_should_use() -\u003e br_multicast_ctx_vlan_disabled(), so\nonce it is cleared under the lock no reader can arm the context again.\n\nFor a master VLAN the handshake never runs.  __vlan_del() clears\nBRIDGE_VLAN_INFO_BRENTRY before calling br_vlan_put_master(), so\nbr_multicast_toggle_one_vlan(masterv, false) returns early on\n!br_vlan_is_brentry(vlan): the flag stays set and br-\u003emulticast_lock is\nnever taken.  br_vlan_put_master() then drains the context in\nbr_multicast_ctx_deinit() and frees the VLAN through call_rcu(), while a\nreader still inside rcu_read_lock() sees the context as enabled and\nre-arms it.  The port and port-VLAN branch of the function has no\nbr_vlan_is_brentry() test and flips the flag under br-\u003emulticast_lock,\nso it is not affected.\n\nThe reader is the bridge transmit path.  For a master VLAN\nbr_multicast_rcv() selects brmctx = \u0026vlan-\u003ebr_mcast_ctx with\npmctx = NULL, so IGMP sent to the bridge device re-arms the context's\ntimers after br_multicast_ctx_deinit() has already stopped them.\n\n  BUG: KASAN: slab-use-after-free in detach_if_pending+0x412/0x4a0\n  Write of size 8 at addr ffff88810ac39918 by task brmc/601\n   __mod_timer+0x51a/0xc50\n   br_multicast_host_join+0x25b/0x390\n   __br_multicast_add_group+0x468/0x530\n   br_ip4_multicast_add_group+0x1a0/0x260\n   br_multicast_rcv+0x2cda/0x61e0\n   br_dev_xmit+0x6c4/0x1540\n  Allocated by task 610:\n   br_vlan_add+0x111/0xb40\n   br_vlan_info+0x370/0x3e0\n  Freed by task 0:\n   kfree+0x1a7/0x4f0\n   rcu_core+0x7dc/0x10a0\n\nOnly test br_vlan_is_brentry() when enabling, like the\nbr_multicast_ctx_vlan_global_disabled() test next to it.  Disabling then\nalways clears BR_VLFLAG_MCAST_ENABLED under br-\u003emulticast_lock before\nbr_multicast_ctx_deinit() drains the context.","ecosystems":[],"exploits":{"exploitdb":0,"first_seen":null,"github_poc":0,"max_poc_stars":null,"metasploit":0,"nuclei":0,"refs":[],"tier":"none_known"},"has_fix":true,"headline":"net: bridge: mcast: fix use-after-free of a master VLAN's multicast context","id":"CVE-2026-80842","indexable":true,"kev":null,"kind":"cve","links":{"ecosystem":null,"product":null,"products":[],"type":"use_after_free","year":"2026"},"n_packages":0,"n_references":8,"next":{"headline":"xfrm: fix xfrm_state_construct() auth-trunc leak","id":"CVE-2026-80843"},"packages":[],"prev":{"headline":"net/packet: defer vmalloc TX_RING free until skbs finish","id":"CVE-2026-80841"},"products":["Linux"],"published":"2026-09-04","related":[],"sources":[{"class":"attribution","licence":"CVE Terms of Use (MITRE)","name":"CVE List","prefix":"CVE"}],"ssvc":{"automatable":null,"exploitation":null,"technical_impact":null},"state":"PUBLISHED","updated":"2026-10-19","vendors":["Linux"]},"summary":"A use-after-free in the Linux kernel bridge multicast code allows local attackers to cause denial of service or execute arbitrary code.","url":"https://insights.sbomify.com/CVE-2026-80842/"}