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CVE-2026-63802— blk-cgroup: fix UAF in __blkcg_rstat_flush()

Quick assessment

Affected
Linux Linux
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Linux kernel是美国Linux基金会开源的一款操作系统内核。 Linux kernel 6.3.9版本存在安全漏洞，该漏洞源于释放后重用，当同一blkcg中的多个blkg并发释放时，一个blkg的__blkcg_rstat_flush()通过llist_del_all()移除另一个blkg的iostat条目，导致第二个blkg看到空列表而在第一个blkg仍在遍历条目时释放自身，从而触发释放后重用。

CVSS 7.8 · High EPSS 0.13% · P3

Possible ATT&CK Techniques 1 AI

T1059 · Command and Scripting Interpreter

Affected Version Matrix 14

VendorProduct Version RangeStatus
Linux Linux 20cb1c2fb7568a6054c55defe044311397e01ddb< 96e545410c4f74c89d496c1d5d9ef8d08f14368b affected
20cb1c2fb7568a6054c55defe044311397e01ddb< bbebd9425cad3573d1527441753899b926525a0f affected
20cb1c2fb7568a6054c55defe044311397e01ddb< 5e5b7f2ef854936e95dceb6a2fdfefcb7152d2c6 affected
20cb1c2fb7568a6054c55defe044311397e01ddb< afebe44facc48a61761e885bbb7f0380d4a603ec affected
20cb1c2fb7568a6054c55defe044311397e01ddb< 0ab5ee5a1badb58cbb2242617cb01a4972b1f2a2 affected
0f6090d90f627d8c58f939067d6c6821ce1b3c68 affected
6.3.9< 6.4 affected
6.4 affected
… +6 more rows
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I. Basic Information for CVE-2026-63802

Vulnerability Information
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Vulnerability Title
blk-cgroup: fix UAF in __blkcg_rstat_flush()
Source: CVE Program / CVE List V5
Vulnerability 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.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Source: CVE Program / CVE List V5
Vulnerability Type
N/A
Source: CVE Program / CVE List V5
Vulnerability Title
Linux kernel 安全漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Linux kernel是美国Linux基金会开源的一款操作系统内核。 Linux kernel 6.3.9版本存在安全漏洞，该漏洞源于释放后重用，当同一blkcg中的多个blkg并发释放时，一个blkg的__blkcg_rstat_flush()通过llist_del_all()移除另一个blkg的iostat条目，导致第二个blkg看到空列表而在第一个blkg仍在遍历条目时释放自身，从而触发释放后重用。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
Linux Linux 20cb1c2fb7568a6054c55defe044311397e01ddb ~ 96e545410c4f74c89d496c1d5d9ef8d08f14368b -
Linux Linux 6.4 -

II. Public POCs for CVE-2026-63802

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III. Intelligence Information for CVE-2026-63802

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Patches & Fixes for CVE-2026-63802 (5)

Same Patch Batch · Linux · 2026-07-19 · 429 CVEs total

CVE-2026-63795 10.0 CRITICAL 9p: avoid putting oldfid in p9_client_walk() error path
CVE-2026-64091 9.8 CRITICAL batman-adv: tt: fix TOCTOU race for reported vlans
CVE-2026-63984 9.8 CRITICAL ipv6: rpl: fix hdrlen overflow in ipv6_rpl_srh_decompress()
CVE-2026-64025 9.8 CRITICAL bpf, skmsg: fix verdict sk_data_ready racing with ktls rx
CVE-2026-63922 9.8 CRITICAL ipv6: exthdrs: refresh nh after handling HAO option
CVE-2026-63979 9.8 CRITICAL net/handshake: hand off the pinned file reference to accept_doit
CVE-2026-64056 9.8 CRITICAL net: ethernet: cortina: Make RX SKB per-port
CVE-2026-63800 9.8 CRITICAL pNFS: Fix use-after-free in pnfs_update_layout()
CVE-2026-63978 9.8 CRITICAL net/handshake: Drain pending requests at net namespace exit
CVE-2026-64055 9.8 CRITICAL net: ethernet: cortina: Carry over frag counter
CVE-2026-63808 9.8 CRITICAL exfat: fix potential use-after-free in exfat_find_dir_entry()
CVE-2026-64033 9.8 CRITICAL RDMA/rtrs: Fix use-after-free in path file creation cleanup
CVE-2026-63888 9.8 CRITICAL scsi: target: iscsi: Fix CRC overread and double-free in iscsit_handle_text_cmd()
CVE-2026-63887 9.8 CRITICAL scsi: target: iscsi: Bound iscsi_encode_text_output() appends to rsp_buf
CVE-2026-64113 9.8 CRITICAL ixgbevf: fix use-after-free in VEPA multicast source pruning
CVE-2026-63825 9.8 CRITICAL gcov: use atomic counter updates to fix concurrent access crashes
CVE-2026-63857 9.8 CRITICAL net: airoha: Do not read uninitialized fragment address in airoha_dev_xmit()
CVE-2026-64160 9.8 CRITICAL netfs: Fix potential for tearing in ->remote_i_size and ->zero_point
CVE-2026-64125 9.8 CRITICAL net: bcmgenet: keep RBUF EEE/PM disabled
CVE-2026-63924 9.8 CRITICAL ipv6: exthdrs: refresh nh pointer after ipv6_hop_jumbo()

Showing top 20 of 429 CVEs. View all on vendor page &rarr; →

IV. Related Vulnerabilities

Same product: Linux
Same vendor: Linux

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