{"id":"CVE-2026-63892","state":"PUBLISHED","title":"thunderbolt: property: Reject dir_len < 4 to prevent size_t underflow","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nthunderbolt: property: Reject dir_len < 4 to prevent size_t underflow\n\nOn the non-root path, __tb_property_parse_dir() takes dir_len from\nentry->length (u16 widened to size_t).  Two distinct OOB conditions\nfollow when entry->length < 4:\n\n1. The non-root path begins with kmemdup(&block[dir_offset],\n   sizeof(*dir->uuid), ...) which always reads 4 dwords from\n   dir_offset.  tb_property_entry_valid() only enforces\n   dir_offset + entry->length <= block_len, so a crafted entry\n   with dir_offset close to the end of the property block and\n   entry->length in 0..3 passes that gate but lets the UUID copy\n   run off the block (e.g. dir_offset = 497, dir_len = 3 in a\n   500-dword block reads block[497..501]).\n\n2. After the kmemdup, content_len = dir_len - 4 underflows size_t\n   to ~SIZE_MAX, nentries becomes SIZE_MAX / 4, and the entry\n   walk runs OOB on each iteration until an entry fails\n   validation or the kernel oopses on an unmapped page.\n\nReject dir_len < 4 on the non-root path *before* the UUID kmemdup,\nwhich closes both holes.\n\nAlso move INIT_LIST_HEAD(&dir->properties) up to immediately after\nthe dir allocation so the new error-return path (and the existing\nuuid-alloc failure path) calling tb_property_free_dir() sees a\nwalkable list rather than the zero-initialized NULL next/prev that\nlist_for_each_entry_safe() would oops on.","publishedAt":"2026-07-19T14:55:03.568Z","updatedAt":"2026-07-19T14:55:03.568Z","severity":null,"assigner":"Linux","products":["Linux Linux"],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"cdae7c07e3e3509eaabc18c1640a55dc5b99c179","status":"affected","lessThan":"37abc4504fa19d8f9f1e87792e8a2b8fdb308e40","versionType":"git"},{"version":"cdae7c07e3e3509eaabc18c1640a55dc5b99c179","status":"affected","lessThan":"e2d4d51cf5785815fa4e91e0c019e3eb2506a84c","versionType":"git"},{"version":"cdae7c07e3e3509eaabc18c1640a55dc5b99c179","status":"affected","lessThan":"de618299190b418291609e6921557253bd417e25","versionType":"git"},{"version":"cdae7c07e3e3509eaabc18c1640a55dc5b99c179","status":"affected","lessThan":"5506c825f14d810f0690b1f4367cb7249ebb387a","versionType":"git"},{"version":"cdae7c07e3e3509eaabc18c1640a55dc5b99c179","status":"affected","lessThan":"542a13890b742099c461d70920e97b14e568f6ec","versionType":"git"},{"version":"cdae7c07e3e3509eaabc18c1640a55dc5b99c179","status":"affected","lessThan":"d548179adcc87e1bc66b17e00352a1f536e76065","versionType":"git"},{"version":"cdae7c07e3e3509eaabc18c1640a55dc5b99c179","status":"affected","lessThan":"3bec49ca55e08fb085cc4318f24b1b37eaab28cb","versionType":"git"},{"version":"cdae7c07e3e3509eaabc18c1640a55dc5b99c179","status":"affected","lessThan":"de21b59c29e31c5108ddc04210631bbfab81b997","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["drivers/thunderbolt/property.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"4.15","status":"affected"},{"version":"0","status":"unaffected","lessThan":"4.15","versionType":"semver"},{"version":"5.10.259","status":"unaffected","lessThanOrEqual":"5.10.*","versionType":"semver"},{"version":"5.15.210","status":"unaffected","lessThanOrEqual":"5.15.*","versionType":"semver"},{"version":"6.1.176","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.6.143","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.93","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.35","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.0.12","status":"unaffected","lessThanOrEqual":"7.0.*","versionType":"semver"},{"version":"7.1","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["drivers/thunderbolt/property.c"]}],"references":["https://git.kernel.org/stable/c/37abc4504fa19d8f9f1e87792e8a2b8fdb308e40","https://git.kernel.org/stable/c/e2d4d51cf5785815fa4e91e0c019e3eb2506a84c","https://git.kernel.org/stable/c/de618299190b418291609e6921557253bd417e25","https://git.kernel.org/stable/c/5506c825f14d810f0690b1f4367cb7249ebb387a","https://git.kernel.org/stable/c/542a13890b742099c461d70920e97b14e568f6ec","https://git.kernel.org/stable/c/d548179adcc87e1bc66b17e00352a1f536e76065","https://git.kernel.org/stable/c/3bec49ca55e08fb085cc4318f24b1b37eaab28cb","https://git.kernel.org/stable/c/de21b59c29e31c5108ddc04210631bbfab81b997"],"weaknesses":[],"ingestedAt":"2026-10-29T20:12:41.951Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/63xxx/CVE-2026-63892.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-63892","state":"PUBLISHED","datePublished":"2026-07-19T14:55:03.568Z","dateUpdated":"2026-07-19T14:55:03.568Z","assignerShortName":"Linux","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateReserved":"2026-07-19T07:54:57.019Z"},"containers":{"cna":{"title":"thunderbolt: property: Reject dir_len < 4 to prevent size_t underflow","descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\nthunderbolt: property: Reject dir_len < 4 to prevent size_t underflow\n\nOn the non-root path, __tb_property_parse_dir() takes dir_len from\nentry->length (u16 widened to size_t).  Two distinct OOB conditions\nfollow when entry->length < 4:\n\n1. The non-root path begins with kmemdup(&block[dir_offset],\n   sizeof(*dir->uuid), ...) which always reads 4 dwords from\n   dir_offset.  tb_property_entry_valid() only enforces\n   dir_offset + entry->length <= block_len, so a crafted entry\n   with dir_offset close to the end of the property block and\n   entry->length in 0..3 passes that gate but lets the UUID copy\n   run off the block (e.g. dir_offset = 497, dir_len = 3 in a\n   500-dword block reads block[497..501]).\n\n2. After the kmemdup, content_len = dir_len - 4 underflows size_t\n   to ~SIZE_MAX, nentries becomes SIZE_MAX / 4, and the entry\n   walk runs OOB on each iteration until an entry fails\n   validation or the kernel oopses on an unmapped page.\n\nReject dir_len < 4 on the non-root path *before* the UUID kmemdup,\nwhich closes both holes.\n\nAlso move INIT_LIST_HEAD(&dir->properties) up to immediately after\nthe dir allocation so the new error-return path (and the existing\nuuid-alloc failure path) calling tb_property_free_dir() sees a\nwalkable list rather than the zero-initialized NULL next/prev that\nlist_for_each_entry_safe() would oops on."}],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"cdae7c07e3e3509eaabc18c1640a55dc5b99c179","status":"affected","lessThan":"37abc4504fa19d8f9f1e87792e8a2b8fdb308e40","versionType":"git"},{"version":"cdae7c07e3e3509eaabc18c1640a55dc5b99c179","status":"affected","lessThan":"e2d4d51cf5785815fa4e91e0c019e3eb2506a84c","versionType":"git"},{"version":"cdae7c07e3e3509eaabc18c1640a55dc5b99c179","status":"affected","lessThan":"de618299190b418291609e6921557253bd417e25","versionType":"git"},{"version":"cdae7c07e3e3509eaabc18c1640a55dc5b99c179","status":"affected","lessThan":"5506c825f14d810f0690b1f4367cb7249ebb387a","versionType":"git"},{"version":"cdae7c07e3e3509eaabc18c1640a55dc5b99c179","status":"affected","lessThan":"542a13890b742099c461d70920e97b14e568f6ec","versionType":"git"},{"version":"cdae7c07e3e3509eaabc18c1640a55dc5b99c179","status":"affected","lessThan":"d548179adcc87e1bc66b17e00352a1f536e76065","versionType":"git"},{"version":"cdae7c07e3e3509eaabc18c1640a55dc5b99c179","status":"affected","lessThan":"3bec49ca55e08fb085cc4318f24b1b37eaab28cb","versionType":"git"},{"version":"cdae7c07e3e3509eaabc18c1640a55dc5b99c179","status":"affected","lessThan":"de21b59c29e31c5108ddc04210631bbfab81b997","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["drivers/thunderbolt/property.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"4.15","status":"affected"},{"version":"0","status":"unaffected","lessThan":"4.15","versionType":"semver"},{"version":"5.10.259","status":"unaffected","lessThanOrEqual":"5.10.*","versionType":"semver"},{"version":"5.15.210","status":"unaffected","lessThanOrEqual":"5.15.*","versionType":"semver"},{"version":"6.1.176","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.6.143","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.93","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.35","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.0.12","status":"unaffected","lessThanOrEqual":"7.0.*","versionType":"semver"},{"version":"7.1","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["drivers/thunderbolt/property.c"]}],"references":[{"url":"https://git.kernel.org/stable/c/37abc4504fa19d8f9f1e87792e8a2b8fdb308e40"},{"url":"https://git.kernel.org/stable/c/e2d4d51cf5785815fa4e91e0c019e3eb2506a84c"},{"url":"https://git.kernel.org/stable/c/de618299190b418291609e6921557253bd417e25"},{"url":"https://git.kernel.org/stable/c/5506c825f14d810f0690b1f4367cb7249ebb387a"},{"url":"https://git.kernel.org/stable/c/542a13890b742099c461d70920e97b14e568f6ec"},{"url":"https://git.kernel.org/stable/c/d548179adcc87e1bc66b17e00352a1f536e76065"},{"url":"https://git.kernel.org/stable/c/3bec49ca55e08fb085cc4318f24b1b37eaab28cb"},{"url":"https://git.kernel.org/stable/c/de21b59c29e31c5108ddc04210631bbfab81b997"}],"providerMetadata":{"shortName":"Linux","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateUpdated":"2026-07-19T14:55:03.568Z"},"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.15","versionEndExcluding":"5.10.259"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.15","versionEndExcluding":"5.15.210"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.15","versionEndExcluding":"6.1.176"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.15","versionEndExcluding":"6.6.143"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.15","versionEndExcluding":"6.12.93"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.15","versionEndExcluding":"6.18.35"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.15","versionEndExcluding":"7.0.12"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.15","versionEndExcluding":"7.1"}]}]}],"x_generator":{"engine":"bippy-1.2.0"}}}}}