{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-63802","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","state":"PUBLISHED","assignerShortName":"Linux","dateReserved":"2026-07-19T07:54:57.013Z","datePublished":"2026-07-19T12:02:08.020Z","dateUpdated":"2026-08-17T04:51:07.787Z"},"containers":{"cna":{"providerMetadata":{"orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","shortName":"Linux","dateUpdated":"2026-08-17T04:51:07.787Z"},"descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\nblk-cgroup: fix UAF in __blkcg_rstat_flush()\n\nWhen multiple blkgs in the same blkcg are released concurrently,\na use-after-free can occur. The race happens when one blkg's\n__blkcg_rstat_flush() removes another blkg's iostat entries via\nllist_del_all(). The second blkg sees an empty list and proceeds\nto free itself while the first is still iterating over its entries.\n\nMove the flush from __blkg_release() (RCU callback) to blkg_release()\n(before call_rcu). This ensures the RCU grace period waits for any\nconcurrent flush's rcu_read_lock() section to complete before freeing."}],"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 cgroup management (rmdir on cgroupfs) and concurrent block I/O to populate per-blkcg rstat lists; the vulnerable code is in the block cgroup teardown path, not in any network protocol handler.\nAC:L - The attacker controls both sides of the race by issuing I/O on multiple block devices to create multiple blkgs with pending stats, then concurrently destroying the cgroup to trigger parallel blkg_release() calls on multiple CPUs.\nPR:L - Triggering cgroup deletion and block I/O requires only delegated cgroup write access or namespace/container root (CAP_SYS_ADMIN in a user namespace), not init-namespace root; this is routinely available in containers, Kubernetes pods, and systemd user cgroup hierarchies.\nUI:N - No victim interaction is required; the attacker programmatically performs I/O and cgroup teardown from their own process or container.\nS:U - The UAF corrupts kernel heap memory within the same kernel security domain; it does not inherently cross a VM, container, or IOMMU boundary without a separate privilege-escalation step.\nC:H - The use-after-free dereferences freed blkg structures and associated iostat data during list iteration, enabling arbitrary kernel memory read primitives typical of slab UAF bugs.\nI:H - UAF on kmalloc-allocated blkg objects allows heap grooming and write through dangling pointers, which can be leveraged for arbitrary kernel memory modification or code execution.\nA:H - Concurrent use-after-free during blkg teardown can cause immediate kernel oops/panic from accessing freed memory, and repeated triggering enables reliable denial of service."}]}],"affected":[{"product":"Linux","vendor":"Linux","defaultStatus":"unaffected","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["block/blk-cgroup.c"],"versions":[{"version":"20cb1c2fb7568a6054c55defe044311397e01ddb","lessThan":"96e545410c4f74c89d496c1d5d9ef8d08f14368b","status":"affected","versionType":"git"},{"version":"20cb1c2fb7568a6054c55defe044311397e01ddb","lessThan":"bbebd9425cad3573d1527441753899b926525a0f","status":"affected","versionType":"git"},{"version":"20cb1c2fb7568a6054c55defe044311397e01ddb","lessThan":"5e5b7f2ef854936e95dceb6a2fdfefcb7152d2c6","status":"affected","versionType":"git"},{"version":"20cb1c2fb7568a6054c55defe044311397e01ddb","lessThan":"afebe44facc48a61761e885bbb7f0380d4a603ec","status":"affected","versionType":"git"},{"version":"20cb1c2fb7568a6054c55defe044311397e01ddb","lessThan":"0ab5ee5a1badb58cbb2242617cb01a4972b1f2a2","status":"affected","versionType":"git"},{"version":"0f6090d90f627d8c58f939067d6c6821ce1b3c68","status":"affected","versionType":"git"},{"version":"6.3.9","lessThan":"6.4","status":"affected","versionType":"semver"}]},{"product":"Linux","vendor":"Linux","defaultStatus":"affected","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["block/blk-cgroup.c"],"versions":[{"version":"6.4","status":"affected"},{"version":"0","lessThan":"6.4","status":"unaffected","versionType":"semver"},{"version":"6.6.144","lessThanOrEqual":"6.6.*","status":"unaffected","versionType":"semver"},{"version":"6.12.95","lessThanOrEqual":"6.12.*","status":"unaffected","versionType":"semver"},{"version":"6.18.38","lessThanOrEqual":"6.18.*","status":"unaffected","versionType":"semver"},{"version":"7.1.3","lessThanOrEqual":"7.1.*","status":"unaffected","versionType":"semver"},{"version":"7.2","lessThanOrEqual":"*","status":"unaffected","versionType":"original_commit_for_fix"}]}],"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.4","versionEndExcluding":"6.6.144"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.4","versionEndExcluding":"6.12.95"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.4","versionEndExcluding":"6.18.38"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.4","versionEndExcluding":"7.1.3"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.4","versionEndExcluding":"7.2"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.3.9"}]}]}],"references":[{"url":"https://git.kernel.org/stable/c/96e545410c4f74c89d496c1d5d9ef8d08f14368b"},{"url":"https://git.kernel.org/stable/c/bbebd9425cad3573d1527441753899b926525a0f"},{"url":"https://git.kernel.org/stable/c/5e5b7f2ef854936e95dceb6a2fdfefcb7152d2c6"},{"url":"https://git.kernel.org/stable/c/afebe44facc48a61761e885bbb7f0380d4a603ec"},{"url":"https://git.kernel.org/stable/c/0ab5ee5a1badb58cbb2242617cb01a4972b1f2a2"}],"title":"blk-cgroup: fix UAF in __blkcg_rstat_flush()","x_generator":{"engine":"bippy-1.2.0"}}}}