{ "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" } } } }