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CVE-2026-89655— ceph: fix UAF in __kick_flushing_caps() on cf entry freed during unlock

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.

以下是该 Linux 内核漏洞描述的中文翻译： 在 Linux 内核中，已修复以下漏洞： ceph: 修复 中因 cf 条目在解锁期间被释放导致的 UAF（Use-After-Free，释放后使用）问题 宏在遍历 时会暂时释放 以发送 cap 消息。在这个解锁的时间窗口内， 可能会重新获取 ，将 的 cf 条目从列表中分离出来，释放 ，并在任何锁之外通过 释放这些条目。当原线程重新获取 且 for 循环宏通过 前进时，它会在已释放的内存上解引用 ，从而导致 UAF。 竞态条件时间线： 该 cf 条目正是由 自己通过

AI Predicted 7.8 Difficulty: Hard

Affected Version Matrix 11

VendorProduct Version RangeStatus
Linux Linux 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2< 2701431aa3cc8b23efe6890182e7b04f5e76fab5 affected
1da177e4c3f41524e886b7f1b8a0c1fc7321cac2< fe46746087b5b9c5bb2d022df6c7819218494ced affected
1da177e4c3f41524e886b7f1b8a0c1fc7321cac2< 2dba24dcd5050be4b7b119e6f0b01f62203b5d26 affected
1da177e4c3f41524e886b7f1b8a0c1fc7321cac2< 7af4c4f01305b0935adf6d4301b1ec407025485d affected
< 6.12.109 affected
< 6.18.50 affected
< 7.2.4 affected
6.12.109≤ 6.12.* unaffected
… +3 more rows
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I. Basic Information for CVE-2026-89655

Vulnerability Information
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Vulnerability Title
ceph: fix UAF in __kick_flushing_caps() on cf entry freed during unlock
Source: CVE Program / CVE List V5
Vulnerability Description
In the Linux kernel, the following vulnerability has been resolved: ceph: fix UAF in __kick_flushing_caps() on cf entry freed during unlock list_for_each_entry() iterates ci->i_cap_flush_list but drops i_ceph_lock to send cap messages. During the unlock window, handle_cap_flush_ack() can acquire i_ceph_lock, detach cf entries with tid <= flush_tid from the list, release i_ceph_lock, and free them via ceph_free_cap_flush() outside any lock. When the original thread reacquires i_ceph_lock and the for-loop macro advances via cf = list_next_entry(cf, i_list), it dereferences cf->i_list.next on freed memory. The race timeline: __kick_flushing_caps() handle_cap_flush_ack() ----------------------- ----------------------- holds i_ceph_lock <--- iterates to cf (tid=10) prepares FLUSH message drops i_ceph_lock <--- __send_cap() ── FLUSH(tid=10) MDS sends FLUSH_ACK(tid=10) ---> acquires i_ceph_lock cf->tid(10) <= flush_tid(10), detaches cf from i_cap_flush_list drops i_ceph_lock ceph_free_cap_flush(cf) <- frees it! acquires i_ceph_lock <--- for-loop advances: cf = list_next_entry(cf, i_list) -- UAF on freed cf->i_list.next The cf was just sent by __kick_flushing_caps itself via __send_cap(). The MDS may respond with FLUSH_ACK quickly enough that handle_cap_flush_ack() frees cf before __kick_flushing_caps can finish the iteration. Fix by converting to a manual while loop: save the next pointer under i_ceph_lock before dropping it, then use the saved pointer after reacquiring, so the potentially-freed cf is never accessed again.
Source: CVE Program / CVE List V5
CVSS Information
N/A
Source: CVE Program / CVE List V5
Vulnerability Type
N/A
Source: CVE Program / CVE List V5

Affected Products

Vendor Product Affected Versions CPE Subscribe
Linux Linux 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 ~ 2701431aa3cc8b23efe6890182e7b04f5e76fab5 -
Linux Linux 6.12.109 ~ 6.12.* -

II. Public POCs for CVE-2026-89655

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III. Intelligence Information for CVE-2026-89655

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Patches & Fixes for CVE-2026-89655 (4)

Same Patch Batch · Linux · 2026-09-11 · 431 CVEs total

CVE-2026-89491 ocfs2: cluster: don't sleep while holding o2hb_live_lock in o2hb_region_pin()
CVE-2026-89477 sctp: fix NULL deref on untransmitted RECONF completion
CVE-2026-89478 sctp: drop a chunk if its transport was removed
CVE-2026-89479 sctp: stop processing a packet once its association is deleted
CVE-2026-89480 nvme-tcp: reject a read that transferred too few bytes
CVE-2026-89482 nvme-tcp: do not accept C2HData based on blk_rq_payload_bytes() alone
CVE-2026-89481 nvme-tcp: fix host memory disclosure on R2T for a read command
CVE-2026-89483 nvme: zero the discard fallback page
CVE-2026-89484 lockd: fix NULL dereference on lockowner allocation failure
CVE-2026-89485 lockd: pin next file across nlm_inspect_file lock-drop
CVE-2026-89486 ipmi: Fix use-after-free of cmd_rcvr in _ipmi_destroy_user()
CVE-2026-89487 openvswitch: only skb_tx_error() a packet we are about to drop
CVE-2026-89488 openvswitch: Fix CT limit teardown use-after-free
CVE-2026-89489 openrisc: fix arbitrary kernel memory access via or1k_atomic syscall
CVE-2026-89500 ring-buffer: Make cpu_buffer::free_page a buffer_data_read_page
CVE-2026-89497 orangefs: skip leading spaces before parsing client debug masks
CVE-2026-89498 orangefs: fix double-free of trailer_buf on readdir copy failure
CVE-2026-89499 ring-buffer: Stop remote reader update when page swap fails
CVE-2026-89496 ocfs2: always run deallocs on copy-on-write completion
CVE-2026-89501 ring-buffer: Hold cpu_buffer::lock when resizing a subbuf

Showing top 20 of 431 CVEs. View all on vendor page &rarr; →

IV. Related Vulnerabilities

Same product: Linux
Same vendor: Linux

V. Comments for CVE-2026-89655

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