CVE-2026-63802: blk-cgroup: fix UAF in __blkcg_rstat_flush()
Vulnerability summary
CVE-2026-63802 is a high (CVSS 7.8) Use After Free vulnerability in linux. EPSS estimates a 0.10% chance of exploitation in the next 30 days, higher than 0.9% of scored vulnerabilities.
Not severe (CVSS 7.8, local access); no exploitation reported by the 5 checked sources
Source freshness unavailable
How is this decided?Advisory lineage
Upstream 0 · Downstream 150 · Related 143Showing 100 of 150.
Timeline
- 19-07-2026PublishedVulnerability first disclosed.
- 19-10-2026Last modifiedVulnerability information updated.
Description
In the Linux kernel, the following vulnerability has been resolved: blk-cgroup: fix UAF in __blkcg_rstat_flush() When multiple blkgs in the same blkcg are released concurrently, a use-after-free can occur. The race happens when one blkg's __blkcg_rstat_flush() removes another blkg's iostat entries via llist_del_all(). The second blkg sees an empty list and proceeds to free itself while the first is still iterating over its entries. Move the flush from __blkg_release() (RCU callback) to blkg_release() (before call_rcu). This ensures the RCU grace period waits for any concurrent flush's rcu_read_lock() section to complete before freeing.
CVSS metrics
4 scores · 4 sources · 1 version- OSV · UbuntuEcosystem advisory · calculated7.8HighCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
- OSV · DebianEcosystem advisory · calculated7.8HighCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
- NVDNIST7.8HighCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
EPSS trend
Probability
0.10%
Chance of exploitation in the next 30 days
Percentile
1%
Versus all other CVEs
30-day change
Decrease -0.03 pp
From 0.13% on 04-10-2026
Known exploited
Compare KEV catalogs
CISA KEVNot in the CISA KEV catalog.
ENISA CNWNot in the ENISA CNW catalog.
CIRCLNot in the CIRCL catalog.
Public exploits
0 foundNo public exploits indexed.
Weaknesses
CWE · root cause- CWE-416Use After FreeThe product reuses or references memory after it has been freed. At some point afterward, the memory may be allocated again and saved in another pointer, while the original pointer references a location somewhere within the new allocation. Any operations using the original pointer are no longer valid because the memory "belongs" to the code that operates on the new pointer.
- CWE-362Concurrent Execution using Shared Resource with Improper SynchronizationThe product contains a concurrent code sequence that requires temporary, exclusive access to a shared resource, but a timing window exists in which the shared resource can be modified by another code sequence operating concurrently.
Affected systems
Known conditions: local access, low-privilege account, no user interaction (CVSS vector). Other conditions: not stated in public data.
Ubuntu142 products
- linuxAll versions (No fix recorded) | < 6.8.0-147.147 | < 7.0.0-31.31
- linux-allwinner-5.19All versions (No fix recorded)
- linux-awsAll versions (No fix recorded) | < 6.8.0-1067.70 | < 7.0.0-1012.12
- linux-aws-5.0All versions (No fix recorded)
- linux-aws-5.11All versions (No fix recorded)
Linux2 products
- linux≥ 20cb1c2fb7568a6054c55defe044311397e01ddb, < 96e545410c4f74c89d496c1d5d9ef8d08f14368b | ≥ 20cb1c2fb7568a6054c55defe044311397e01ddb, < bbebd9425cad3573d1527441753899b926525a0f | ≥ 20cb1c2fb7568a6054c55defe044311397e01ddb, < 5e5b7f2ef854936e95dceb6a2fdfefcb7152d2c6 | ≥ 20cb1c2fb7568a6054c55defe044311397e01ddb, < afebe44facc48a61761e885bbb7f0380d4a603ec | ≥ 20cb1c2fb7568a6054c55defe044311397e01ddb, < 0ab5ee5a1badb58cbb2242617cb01a4972b1f2a2 | 0f6090d90f627d8c58f939067d6c6821ce1b3c68 | ≥ 6.3.9, < 6.4 | 6.4
- linux_kernelEOL≥ 6.3.9, < 6.4 | ≥ 6.4.1, < 6.6.144 | ≥ 6.7, < 6.12.95 | ≥ 6.13, < 6.18.38 | ≥ 6.19, < 7.1.3 | 6.4 | 6.4:rc7
Debian1 product
- linux< 6.12.95-1 | < 7.1.3-1
3 vendors · 145 products
