{"id":"CVE-2026-72042","state":"PUBLISHED","title":"ipmi: Fix user refcount underflow in event delivery","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nipmi: Fix user refcount underflow in event delivery\n\nipmi_alloc_recv_msg(user) takes the temporary user reference owned by the\nreceive message, and ipmi_free_recv_msg() drops it again. If event delivery\nfails after allocating receive messages for earlier users,\nhandle_read_event_rsp() rolls those messages back with\nipmi_free_recv_msg().\n\nThat rollback path still drops user->refcount explicitly after freeing each\nmessage. The extra put can free a user that remains linked on intf->users,\nso later event delivery may dereference a freed user or trip refcount_t's\naddition-on-zero warning when ipmi_alloc_recv_msg() tries to acquire\nanother reference.\n\nRemove the stale explicit put and the now-dead user assignment. Keep the\nlist_del() and ipmi_free_recv_msg() calls; they are the required rollback\noperations.","publishedAt":"2026-08-15T05:52:01.454Z","updatedAt":"2026-08-17T05:39:41.572Z","severity":{"score":7.8,"label":"High","version":"3.1","vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","source":"Linux"},"assigner":"Linux","products":["Linux Linux"],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"b52da4054ee0bf9ecb44996f2c83236ff50b3812","status":"affected","lessThan":"ddbb6e3dc9bb4743de686aa1598c31e745cee76b","versionType":"git"},{"version":"b52da4054ee0bf9ecb44996f2c83236ff50b3812","status":"affected","lessThan":"7be349d4fcc5e065295b83418a22d27a68afbdb6","versionType":"git"},{"version":"b52da4054ee0bf9ecb44996f2c83236ff50b3812","status":"affected","lessThan":"6aa9e61c46465d231e9beddf56af7effd71be682","versionType":"git"},{"version":"f63723ca7d7623f9dae1990973cd158671f03c56","status":"affected","versionType":"git"},{"version":"348121b29594d42d1635648fd3ed31dfa25351d5","status":"affected","versionType":"git"},{"version":"53d6e403affbf6df2c859a0ea00ccfc1e72090ca","status":"affected","versionType":"git"},{"version":"0ed73be9a2547ffb9b5c1d879ad9bfab73d920b5","status":"affected","versionType":"git"},{"version":"6.1.157","status":"affected","lessThan":"6.2","versionType":"semver"},{"version":"6.6.113","status":"affected","lessThan":"6.7","versionType":"semver"},{"version":"6.12.54","status":"affected","lessThan":"6.13","versionType":"semver"},{"version":"6.17.4","status":"affected","lessThan":"6.18","versionType":"semver"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["drivers/char/ipmi/ipmi_msghandler.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"6.18","status":"affected"},{"version":"0","status":"unaffected","lessThan":"6.18","versionType":"semver"},{"version":"6.18.40","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.1.5","status":"unaffected","lessThanOrEqual":"7.1.*","versionType":"semver"},{"version":"7.2","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["drivers/char/ipmi/ipmi_msghandler.c"]}],"references":["https://git.kernel.org/stable/c/ddbb6e3dc9bb4743de686aa1598c31e745cee76b","https://git.kernel.org/stable/c/7be349d4fcc5e065295b83418a22d27a68afbdb6","https://git.kernel.org/stable/c/6aa9e61c46465d231e9beddf56af7effd71be682"],"weaknesses":[],"ingestedAt":"2026-10-29T20:12:58.252Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/72xxx/CVE-2026-72042.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-72042","state":"PUBLISHED","datePublished":"2026-08-15T05:52:01.454Z","dateUpdated":"2026-08-17T05:39:41.572Z","assignerShortName":"Linux","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateReserved":"2026-08-09T03:40:39.902Z"},"containers":{"cna":{"title":"ipmi: Fix user refcount underflow in event delivery","descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\nipmi: Fix user refcount underflow in event delivery\n\nipmi_alloc_recv_msg(user) takes the temporary user reference owned by the\nreceive message, and ipmi_free_recv_msg() drops it again. If event delivery\nfails after allocating receive messages for earlier users,\nhandle_read_event_rsp() rolls those messages back with\nipmi_free_recv_msg().\n\nThat rollback path still drops user->refcount explicitly after freeing each\nmessage. The extra put can free a user that remains linked on intf->users,\nso later event delivery may dereference a freed user or trip refcount_t's\naddition-on-zero warning when ipmi_alloc_recv_msg() tries to acquire\nanother reference.\n\nRemove the stale explicit put and the now-dead user assignment. Keep the\nlist_del() and ipmi_free_recv_msg() calls; they are the required rollback\noperations."}],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"b52da4054ee0bf9ecb44996f2c83236ff50b3812","status":"affected","lessThan":"ddbb6e3dc9bb4743de686aa1598c31e745cee76b","versionType":"git"},{"version":"b52da4054ee0bf9ecb44996f2c83236ff50b3812","status":"affected","lessThan":"7be349d4fcc5e065295b83418a22d27a68afbdb6","versionType":"git"},{"version":"b52da4054ee0bf9ecb44996f2c83236ff50b3812","status":"affected","lessThan":"6aa9e61c46465d231e9beddf56af7effd71be682","versionType":"git"},{"version":"f63723ca7d7623f9dae1990973cd158671f03c56","status":"affected","versionType":"git"},{"version":"348121b29594d42d1635648fd3ed31dfa25351d5","status":"affected","versionType":"git"},{"version":"53d6e403affbf6df2c859a0ea00ccfc1e72090ca","status":"affected","versionType":"git"},{"version":"0ed73be9a2547ffb9b5c1d879ad9bfab73d920b5","status":"affected","versionType":"git"},{"version":"6.1.157","status":"affected","lessThan":"6.2","versionType":"semver"},{"version":"6.6.113","status":"affected","lessThan":"6.7","versionType":"semver"},{"version":"6.12.54","status":"affected","lessThan":"6.13","versionType":"semver"},{"version":"6.17.4","status":"affected","lessThan":"6.18","versionType":"semver"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["drivers/char/ipmi/ipmi_msghandler.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"6.18","status":"affected"},{"version":"0","status":"unaffected","lessThan":"6.18","versionType":"semver"},{"version":"6.18.40","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.1.5","status":"unaffected","lessThanOrEqual":"7.1.*","versionType":"semver"},{"version":"7.2","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["drivers/char/ipmi/ipmi_msghandler.c"]}],"references":[{"url":"https://git.kernel.org/stable/c/ddbb6e3dc9bb4743de686aa1598c31e745cee76b"},{"url":"https://git.kernel.org/stable/c/7be349d4fcc5e065295b83418a22d27a68afbdb6"},{"url":"https://git.kernel.org/stable/c/6aa9e61c46465d231e9beddf56af7effd71be682"}],"metrics":[{"cvssV3_1":{"version":"3.1","vectorString":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","baseScore":7.8,"baseSeverity":"HIGH"},"scenarios":[{"lang":"en","value":"AV:L - Exploitation requires local setup via /dev/ipmiN (open, IPMICTL_SET_GETS_EVENTS, message flooding); the refcount bug is in handle_read_event_rsp() during host-side BMC event processing, not via a remote packet path to the kernel.\nAC:L - An attacker with IPMI device access controls both sides: multiple fds, gets_events registration, filling one user's outstanding-message limit to force EBUSY, and generating/waiting for BMC events via their own IPMI commands.\nPR:L - ipmi_open/ipmi_create_user perform no capability() check; access is gated only by /dev/ipmiN DAC, and BMC-equipped servers often grant that node to a non-root management group (ipmi) for ipmitool/freeipmi.\nUI:N - No victim interaction is required; the attacker drives all setup and triggering through their own IPMI file descriptors and ioctls.\nS:U - This is a host-kernel heap use-after-free of struct ipmi_user within the same OS security authority, with no VM escape, IOMMU bypass, or sandbox boundary crossing.\nC:H - Premature free_ipmi_user() leaves a dangling ipmi_user on intf->users; later iterations call kref_get and read handler pointers from freed slab memory, yielding arbitrary kernel read primitives per UAF guidance.\nI:H - Freed ipmi_user objects contain function pointers (handler->ipmi_recv_hndl); smi_work later invokes these on reclaimed memory, enabling heap spray and control-flow hijack for arbitrary kernel write/code execution.\nA:H - The extra kref_put causes refcount underflow warnings and use-after-free of ipmi_user; subsequent event delivery dereferences freed memory and readily triggers kernel oops/panic under KASAN/poisoning."}]}],"providerMetadata":{"shortName":"Linux","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateUpdated":"2026-08-17T05:39:41.572Z"},"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.18","versionEndExcluding":"6.18.40"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.18","versionEndExcluding":"7.1.5"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.18","versionEndExcluding":"7.2"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.1.157"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.6.113"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.12.54"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.17.4"}]}]}],"x_generator":{"engine":"bippy-1.2.0"}}}}}