{ "schemaVersion": 1, "attribution": [ { "source": "CISA Known Exploited Vulnerabilities", "url": "https://www.cisa.gov/known-exploited-vulnerabilities-catalog", "licence": "US government work" }, { "source": "GitHub Advisory Database", "url": "https://github.com/advisories", "licence": "CC BY 4.0" }, { "source": "Have I Been Pwned", "url": "https://haveibeenpwned.com/", "licence": "CC BY 4.0" }, { "source": "CVE Program (CVE records)", "url": "https://www.cve.org/Legal/TermsOfUse", "licence": "CVE Terms of Use", "notice": "Copyright © 1999-2026, The MITRE Corporation. CVE is a trademark and the CVE logo is a registered trademark of The MITRE Corporation.", "terms": "CVE Usage: MITRE hereby grants you a perpetual, worldwide, non-exclusive, no-charge, royalty-free, irrevocable copyright license to reproduce, prepare derivative works of, publicly display, publicly perform, sublicense, and distribute Common Vulnerabilities and Exposures (CVE™). Any copy you make for such purposes is authorized provided that you reproduce MITRE's copyright designation and this license in any such copy." }, { "source": "FIRST EPSS", "url": "https://www.first.org/epss/", "licence": "free to use; FIRST requests attribution" } ], "record": { "id": "CVE-2024-55916", "sourceURL": "https://www.cve.org/CVERecord?id=CVE-2024-55916", "idYear": 2024, "status": "PUBLISHED", "publishedAt": "2025-01-11T12:35:44.800Z", "updatedAt": "2026-05-11T20:53:57.302Z", "importedAt": "2026-10-24T01:57:20.494Z", "snapshot": { "id": "cve_2026-10-24_midnight_baseline", "at": "2026-10-24T00:00:00.000Z", "source": "https://github.com/CVEProject/cvelistV5/releases/tag/cve_2026-10-24_0100Z" }, "facts": { "title": "Drivers: hv: util: Avoid accessing a ringbuffer not initialized yet", "summary": "In the Linux kernel, the following vulnerability has been resolved:\n\nDrivers: hv: util: Avoid accessing a ringbuffer not initialized yet\n\nIf the KVP (or VSS) daemon starts before the VMBus channel's ringbuffer is\nfully initialized, we can hit the panic below:\n\nhv_utils: Registering HyperV Utility Driver\nhv_vmbus: registering driver hv_utils\n...\nBUG: kernel NULL pointer dereference, address: 0000000000000000\nCPU: 44 UID: 0 PID: 2552 Comm: hv_kvp_daemon Tainted: G E 6.11.0-rc3+ #1\nRIP: 0010:hv_pkt_iter_first+0x12/0xd0\nCall Trace:\n...\n vmbus_recvpacket\n hv_kvp_onchannelcallback\n vmbus_on_event\n tasklet_action_common\n tasklet_action\n handle_softirqs\n irq_exit_rcu\n sysvec_hyperv_stimer0\n \n \n asm_sysvec_hyperv_stimer0\n...\n kvp_register_done\n hvt_op_read\n vfs_read\n ksys_read\n __x64_sys_read\n\nThis can happen because the KVP/VSS channel callback can be invoked\neven before the channel is fully opened:\n1) as soon as hv_kvp_init() -> hvutil_transport_init() creates\n/dev/vmbus/hv_kvp, the kvp daemon can open the device file immediately and\nregister itself to the driver by writing a message KVP_OP_REGISTER1 to the\nfile (which is handled by kvp_on_msg() ->kvp_handle_handshake()) and\nreading the file for the driver's response, which is handled by\nhvt_op_read(), which calls hvt->on_read(), i.e. kvp_register_done().\n\n2) the problem with kvp_register_done() is that it can cause the\nchannel callback to be called even before the channel is fully opened,\nand when the channel callback is starting to run, util_probe()->\nvmbus_open() may have not initialized the ringbuffer yet, so the\ncallback can hit the panic of NULL pointer dereference.\n\nTo reproduce the panic consistently, we can add a \"ssleep(10)\" for KVP in\n__vmbus_open(), just before the first hv_ringbuffer_init(), and then we\nunload and reload the driver hv_utils, and run the daemon manually within\nthe 10 seconds.\n\nFix the panic by reordering the steps in util_probe() so the char dev\nentry used by the KVP or VSS daemon is not created until after\nvmbus_open() has completed. This reordering prevents the race condition\nfrom happening.", "affected": [ { "vendor": "Linux", "product": "Linux", "defaultStatus": "unaffected", "versions": [ { "version": "e0fa3e5e7df61eb2c339c9f0067c202c0cdeec2c", "status": "affected", "versionType": "git", "lessThan": "f091a224a2c82f1e302b1768d73bb6332f687321" }, { "version": "e0fa3e5e7df61eb2c339c9f0067c202c0cdeec2c", "status": "affected", "versionType": "git", "lessThan": "d81f4e73aff9b861671df60e5100ad25cc16fbf8" }, { "version": "e0fa3e5e7df61eb2c339c9f0067c202c0cdeec2c", "status": "affected", "versionType": "git", "lessThan": "042253c57be901bfd19f15b68267442b70f510d5" }, { "version": "e0fa3e5e7df61eb2c339c9f0067c202c0cdeec2c", "status": "affected", "versionType": "git", "lessThan": "718fe694a334be9d1a89eed22602369ac18d6583" }, { "version": "e0fa3e5e7df61eb2c339c9f0067c202c0cdeec2c", "status": "affected", "versionType": "git", "lessThan": "89fcec5e466b3ac9b376e0d621c71effa1a7983f" }, { "version": "e0fa3e5e7df61eb2c339c9f0067c202c0cdeec2c", "status": "affected", "versionType": "git", "lessThan": "3dd7a30c6d7f90afcf19e9b072f572ba524d7ec6" }, { "version": "e0fa3e5e7df61eb2c339c9f0067c202c0cdeec2c", "status": "affected", "versionType": "git", "lessThan": "07a756a49f4b4290b49ea46e089cbe6f79ff8d26" } ] }, { "vendor": "Linux", "product": "Linux", "defaultStatus": "affected", "versions": [ { "version": "4.9", "status": "affected" }, { "version": "0", "status": "unaffected", "versionType": "semver", "lessThan": "4.9" }, { "version": "5.4.289", "status": "unaffected", "versionType": "semver", "lessThanOrEqual": "5.4.*" }, { "version": "5.10.233", "status": "unaffected", "versionType": "semver", "lessThanOrEqual": "5.10.*" }, { "version": "5.15.176", "status": "unaffected", "versionType": "semver", "lessThanOrEqual": "5.15.*" }, { "version": "6.1.122", "status": "unaffected", "versionType": "semver", "lessThanOrEqual": "6.1.*" }, { "version": "6.6.68", "status": "unaffected", "versionType": "semver", "lessThanOrEqual": "6.6.*" }, { "version": "6.12.7", "status": "unaffected", "versionType": "semver", "lessThanOrEqual": "6.12.*" }, { "version": "6.13", "status": "unaffected", "versionType": "original_commit_for_fix", "lessThanOrEqual": "*" } ] } ] } } }