{"api_version":"1","generated_at":"2026-04-19T01:12:30+00:00","cve":"CVE-2026-23352","urls":{"html":"https://cve.report/CVE-2026-23352","api":"https://cve.report/api/cve/CVE-2026-23352.json","docs":"https://cve.report/api","cve_org":"https://www.cve.org/CVERecord?id=CVE-2026-23352","nvd":"https://nvd.nist.gov/vuln/detail/CVE-2026-23352"},"summary":{"title":"x86/efi: defer freeing of boot services memory","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nx86/efi: defer freeing of boot services memory\n\nefi_free_boot_services() frees memory occupied by EFI_BOOT_SERVICES_CODE\nand EFI_BOOT_SERVICES_DATA using memblock_free_late().\n\nThere are two issue with that: memblock_free_late() should be used for\nmemory allocated with memblock_alloc() while the memory reserved with\nmemblock_reserve() should be freed with free_reserved_area().\n\nMore acutely, with CONFIG_DEFERRED_STRUCT_PAGE_INIT=y\nefi_free_boot_services() is called before deferred initialization of the\nmemory map is complete.\n\nBenjamin Herrenschmidt reports that this causes a leak of ~140MB of\nRAM on EC2 t3a.nano instances which only have 512MB or RAM.\n\nIf the freed memory resides in the areas that memory map for them is\nstill uninitialized, they won't be actually freed because\nmemblock_free_late() calls memblock_free_pages() and the latter skips\nuninitialized pages.\n\nUsing free_reserved_area() at this point is also problematic because\n__free_page() accesses the buddy of the freed page and that again might\nend up in uninitialized part of the memory map.\n\nDelaying the entire efi_free_boot_services() could be problematic\nbecause in addition to freeing boot services memory it updates\nefi.memmap without any synchronization and that's undesirable late in\nboot when there is concurrency.\n\nMore robust approach is to only defer freeing of the EFI boot services\nmemory.\n\nSplit efi_free_boot_services() in two. First efi_unmap_boot_services()\ncollects ranges that should be freed into an array then\nefi_free_boot_services() later frees them after deferred init is complete.","state":"PUBLISHED","assigner":"Linux","published_at":"2026-03-25 11:16:33","updated_at":"2026-04-18 09:16:20"},"problem_types":[],"metrics":[],"references":[{"url":"https://git.kernel.org/stable/c/a4b0bf6a40f3c107c67a24fbc614510ef5719980","name":"https://git.kernel.org/stable/c/a4b0bf6a40f3c107c67a24fbc614510ef5719980","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/4a2cb90c538f06c873a187aa743575d48685d7a6","name":"https://git.kernel.org/stable/c/4a2cb90c538f06c873a187aa743575d48685d7a6","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/f9e9cc320854a76a39e7bc92d144554f3a727fad","name":"https://git.kernel.org/stable/c/f9e9cc320854a76a39e7bc92d144554f3a727fad","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/399da820ecfe6f4f10c143e5c453d3559a04db9c","name":"https://git.kernel.org/stable/c/399da820ecfe6f4f10c143e5c453d3559a04db9c","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/6d8ba221e7aafaa2f284b7d22faee814c28e009d","name":"https://git.kernel.org/stable/c/6d8ba221e7aafaa2f284b7d22faee814c28e009d","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/227688312fece0026fc67a00ba9a0b3611ebe95d","name":"https://git.kernel.org/stable/c/227688312fece0026fc67a00ba9a0b3611ebe95d","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/7131bd1fecc749bc94fb44aae217bbd8a8a85264","name":"https://git.kernel.org/stable/c/7131bd1fecc749bc94fb44aae217bbd8a8a85264","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/7dcf59422a3b0d20ddda844f856b4a1e0608a326","name":"https://git.kernel.org/stable/c/7dcf59422a3b0d20ddda844f856b4a1e0608a326","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/6a25e25279282c5c8ade554c04c6ab9dc7902c64","name":"https://git.kernel.org/stable/c/6a25e25279282c5c8ade554c04c6ab9dc7902c64","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-23352","name":"CVE Program record","refsource":"CVE.ORG","tags":["canonical"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-23352","name":"NVD vulnerability detail","refsource":"NVD","tags":["canonical","analysis"]}],"affected":[{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 0aed459e8487eb6ebdb4efe8cefe1eafbc704b30 4a2cb90c538f06c873a187aa743575d48685d7a6 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 916f676f8dc016103f983c7ec54c18ecdbb6e349 7131bd1fecc749bc94fb44aae217bbd8a8a85264 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 916f676f8dc016103f983c7ec54c18ecdbb6e349 6d8ba221e7aafaa2f284b7d22faee814c28e009d git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 916f676f8dc016103f983c7ec54c18ecdbb6e349 227688312fece0026fc67a00ba9a0b3611ebe95d git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 916f676f8dc016103f983c7ec54c18ecdbb6e349 6a25e25279282c5c8ade554c04c6ab9dc7902c64 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 916f676f8dc016103f983c7ec54c18ecdbb6e349 399da820ecfe6f4f10c143e5c453d3559a04db9c git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 916f676f8dc016103f983c7ec54c18ecdbb6e349 f9e9cc320854a76a39e7bc92d144554f3a727fad git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 916f676f8dc016103f983c7ec54c18ecdbb6e349 7dcf59422a3b0d20ddda844f856b4a1e0608a326 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 916f676f8dc016103f983c7ec54c18ecdbb6e349 a4b0bf6a40f3c107c67a24fbc614510ef5719980 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 3.0","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 3.0 semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 2.6.39.2 2.6.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 5.10.253 5.10.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 5.15.203 5.15.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 6.1.167 6.1.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 6.6.130 6.6.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 6.12.77 6.12.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 6.18.17 6.18.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 6.19.7 6.19.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 7.0 * original_commit_for_fix","platforms":[]}],"timeline":[],"solutions":[],"workarounds":[],"exploits":[],"credits":[],"nvd_cpes":[],"vendor_comments":[],"enrichments":{"kev":null,"epss":{"cve_year":"2026","cve_id":"23352","cve":"CVE-2026-23352","epss":"0.000430000","percentile":"0.131160000","score_date":"2026-04-18","updated_at":"2026-04-19 00:10:43"},"legacy_qids":[]},"source_records":{"cve_program":{"containers":{"cna":{"affected":[{"defaultStatus":"unaffected","product":"Linux","programFiles":["arch/x86/include/asm/efi.h","arch/x86/platform/efi/efi.c","arch/x86/platform/efi/quirks.c","drivers/firmware/efi/mokvar-table.c"],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","vendor":"Linux","versions":[{"lessThan":"4a2cb90c538f06c873a187aa743575d48685d7a6","status":"affected","version":"0aed459e8487eb6ebdb4efe8cefe1eafbc704b30","versionType":"git"},{"lessThan":"7131bd1fecc749bc94fb44aae217bbd8a8a85264","status":"affected","version":"916f676f8dc016103f983c7ec54c18ecdbb6e349","versionType":"git"},{"lessThan":"6d8ba221e7aafaa2f284b7d22faee814c28e009d","status":"affected","version":"916f676f8dc016103f983c7ec54c18ecdbb6e349","versionType":"git"},{"lessThan":"227688312fece0026fc67a00ba9a0b3611ebe95d","status":"affected","version":"916f676f8dc016103f983c7ec54c18ecdbb6e349","versionType":"git"},{"lessThan":"6a25e25279282c5c8ade554c04c6ab9dc7902c64","status":"affected","version":"916f676f8dc016103f983c7ec54c18ecdbb6e349","versionType":"git"},{"lessThan":"399da820ecfe6f4f10c143e5c453d3559a04db9c","status":"affected","version":"916f676f8dc016103f983c7ec54c18ecdbb6e349","versionType":"git"},{"lessThan":"f9e9cc320854a76a39e7bc92d144554f3a727fad","status":"affected","version":"916f676f8dc016103f983c7ec54c18ecdbb6e349","versionType":"git"},{"lessThan":"7dcf59422a3b0d20ddda844f856b4a1e0608a326","status":"affected","version":"916f676f8dc016103f983c7ec54c18ecdbb6e349","versionType":"git"},{"lessThan":"a4b0bf6a40f3c107c67a24fbc614510ef5719980","status":"affected","version":"916f676f8dc016103f983c7ec54c18ecdbb6e349","versionType":"git"}]},{"defaultStatus":"affected","product":"Linux","programFiles":["arch/x86/include/asm/efi.h","arch/x86/platform/efi/efi.c","arch/x86/platform/efi/quirks.c","drivers/firmware/efi/mokvar-table.c"],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","vendor":"Linux","versions":[{"status":"affected","version":"3.0"},{"lessThan":"3.0","status":"unaffected","version":"0","versionType":"semver"},{"lessThanOrEqual":"2.6.*","status":"unaffected","version":"2.6.39.2","versionType":"semver"},{"lessThanOrEqual":"5.10.*","status":"unaffected","version":"5.10.253","versionType":"semver"},{"lessThanOrEqual":"5.15.*","status":"unaffected","version":"5.15.203","versionType":"semver"},{"lessThanOrEqual":"6.1.*","status":"unaffected","version":"6.1.167","versionType":"semver"},{"lessThanOrEqual":"6.6.*","status":"unaffected","version":"6.6.130","versionType":"semver"},{"lessThanOrEqual":"6.12.*","status":"unaffected","version":"6.12.77","versionType":"semver"},{"lessThanOrEqual":"6.18.*","status":"unaffected","version":"6.18.17","versionType":"semver"},{"lessThanOrEqual":"6.19.*","status":"unaffected","version":"6.19.7","versionType":"semver"},{"lessThanOrEqual":"*","status":"unaffected","version":"7.0","versionType":"original_commit_for_fix"}]}],"cpeApplicability":[{"nodes":[{"cpeMatch":[{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"2.6.39.2","versionStartIncluding":"2.6.39.1","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"5.10.253","versionStartIncluding":"3.0","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"5.15.203","versionStartIncluding":"3.0","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"6.1.167","versionStartIncluding":"3.0","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"6.6.130","versionStartIncluding":"3.0","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"6.12.77","versionStartIncluding":"3.0","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"6.18.17","versionStartIncluding":"3.0","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"6.19.7","versionStartIncluding":"3.0","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"7.0","versionStartIncluding":"3.0","vulnerable":true}],"negate":false,"operator":"OR"}]}],"descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\nx86/efi: defer freeing of boot services memory\n\nefi_free_boot_services() frees memory occupied by EFI_BOOT_SERVICES_CODE\nand EFI_BOOT_SERVICES_DATA using memblock_free_late().\n\nThere are two issue with that: memblock_free_late() should be used for\nmemory allocated with memblock_alloc() while the memory reserved with\nmemblock_reserve() should be freed with free_reserved_area().\n\nMore acutely, with CONFIG_DEFERRED_STRUCT_PAGE_INIT=y\nefi_free_boot_services() is called before deferred initialization of the\nmemory map is complete.\n\nBenjamin Herrenschmidt reports that this causes a leak of ~140MB of\nRAM on EC2 t3a.nano instances which only have 512MB or RAM.\n\nIf the freed memory resides in the areas that memory map for them is\nstill uninitialized, they won't be actually freed because\nmemblock_free_late() calls memblock_free_pages() and the latter skips\nuninitialized pages.\n\nUsing free_reserved_area() at this point is also problematic because\n__free_page() accesses the buddy of the freed page and that again might\nend up in uninitialized part of the memory map.\n\nDelaying the entire efi_free_boot_services() could be problematic\nbecause in addition to freeing boot services memory it updates\nefi.memmap without any synchronization and that's undesirable late in\nboot when there is concurrency.\n\nMore robust approach is to only defer freeing of the EFI boot services\nmemory.\n\nSplit efi_free_boot_services() in two. First efi_unmap_boot_services()\ncollects ranges that should be freed into an array then\nefi_free_boot_services() later frees them after deferred init is complete."}],"providerMetadata":{"dateUpdated":"2026-04-18T08:58:06.719Z","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","shortName":"Linux"},"references":[{"url":"https://git.kernel.org/stable/c/4a2cb90c538f06c873a187aa743575d48685d7a6"},{"url":"https://git.kernel.org/stable/c/7131bd1fecc749bc94fb44aae217bbd8a8a85264"},{"url":"https://git.kernel.org/stable/c/6d8ba221e7aafaa2f284b7d22faee814c28e009d"},{"url":"https://git.kernel.org/stable/c/227688312fece0026fc67a00ba9a0b3611ebe95d"},{"url":"https://git.kernel.org/stable/c/6a25e25279282c5c8ade554c04c6ab9dc7902c64"},{"url":"https://git.kernel.org/stable/c/399da820ecfe6f4f10c143e5c453d3559a04db9c"},{"url":"https://git.kernel.org/stable/c/f9e9cc320854a76a39e7bc92d144554f3a727fad"},{"url":"https://git.kernel.org/stable/c/7dcf59422a3b0d20ddda844f856b4a1e0608a326"},{"url":"https://git.kernel.org/stable/c/a4b0bf6a40f3c107c67a24fbc614510ef5719980"}],"title":"x86/efi: defer freeing of boot services memory","x_generator":{"engine":"bippy-1.2.0"}}},"cveMetadata":{"assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","assignerShortName":"Linux","cveId":"CVE-2026-23352","datePublished":"2026-03-25T10:27:37.500Z","dateReserved":"2026-01-13T15:37:46.000Z","dateUpdated":"2026-04-18T08:58:06.719Z","state":"PUBLISHED"},"dataType":"CVE_RECORD","dataVersion":"5.2"},"nvd":{"publishedDate":"2026-03-25 11:16:33","lastModifiedDate":"2026-04-18 09:16:20","problem_types":[],"metrics":[],"configurations":[]},"legacy_mitre":{"record":{"CveYear":"2026","CveId":"23352","Ordinal":"1","Title":"x86/efi: defer freeing of boot services memory","CVE":"CVE-2026-23352","Year":"2026"},"notes":[{"CveYear":"2026","CveId":"23352","Ordinal":"1","NoteData":"In the Linux kernel, the following vulnerability has been resolved:\n\nx86/efi: defer freeing of boot services memory\n\nefi_free_boot_services() frees memory occupied by EFI_BOOT_SERVICES_CODE\nand EFI_BOOT_SERVICES_DATA using memblock_free_late().\n\nThere are two issue with that: memblock_free_late() should be used for\nmemory allocated with memblock_alloc() while the memory reserved with\nmemblock_reserve() should be freed with free_reserved_area().\n\nMore acutely, with CONFIG_DEFERRED_STRUCT_PAGE_INIT=y\nefi_free_boot_services() is called before deferred initialization of the\nmemory map is complete.\n\nBenjamin Herrenschmidt reports that this causes a leak of ~140MB of\nRAM on EC2 t3a.nano instances which only have 512MB or RAM.\n\nIf the freed memory resides in the areas that memory map for them is\nstill uninitialized, they won't be actually freed because\nmemblock_free_late() calls memblock_free_pages() and the latter skips\nuninitialized pages.\n\nUsing free_reserved_area() at this point is also problematic because\n__free_page() accesses the buddy of the freed page and that again might\nend up in uninitialized part of the memory map.\n\nDelaying the entire efi_free_boot_services() could be problematic\nbecause in addition to freeing boot services memory it updates\nefi.memmap without any synchronization and that's undesirable late in\nboot when there is concurrency.\n\nMore robust approach is to only defer freeing of the EFI boot services\nmemory.\n\nSplit efi_free_boot_services() in two. First efi_unmap_boot_services()\ncollects ranges that should be freed into an array then\nefi_free_boot_services() later frees them after deferred init is complete.","Type":"Description","Title":"x86/efi: defer freeing of boot services memory"}]}}}