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CVE-2026-74658— futex: Prevent robust futex exit race some more

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.

在 Linux 内核中，以下漏洞已得到解决： futex：进一步防止健壮 futex 退出时的竞争条件 健壮 futex（robust futex）解锁操作会将整个 futex 值写为 0，从而清除 FUTEX_WAITERS 位，并唤醒单个等待者。该唤醒操作是一次性通知：协议要求接收方要么获取该 futex（并在意识到存在后续竞争的情况下最终解锁），要么在再次休眠之前重新设置 FUTEX_WAITERS 位。如果被唤醒的等待者在执行上述任一操作之前被杀死，内核必须介入并唤醒队列中的下一个任务。 这是 futex

AI Predicted 5.5 Difficulty: Moderate EPSS 0.22% · P13

Possible ATT&CK Techniques 1 AI

T1055 · Process Injection

Affected Version Matrix 30

VendorProduct Version RangeStatus
Linux Linux ca16d5bee59807bf04deaab0a8eccecd5061528c< 83b0f71d5a313a765754acab51d2ecc5de76e0b9 affected
ca16d5bee59807bf04deaab0a8eccecd5061528c< a1c2b7b86a946b6b172bce44d74553da2323a36c affected
ca16d5bee59807bf04deaab0a8eccecd5061528c< 33bfa85458105d6169ebdb697f692b8bb8025bae affected
ca16d5bee59807bf04deaab0a8eccecd5061528c< aa5c571901c6b22b58373693a4bf889ecab11ff5 affected
ca16d5bee59807bf04deaab0a8eccecd5061528c< 925628656b73b70930972ccde421de4f758d8650 affected
ca16d5bee59807bf04deaab0a8eccecd5061528c< 7b8c53263f8878bdd12c87e147ac6feca5c05211 affected
ca16d5bee59807bf04deaab0a8eccecd5061528c< 7cf710e70f9bb8ea75f759ebed09871801315992 affected
ca16d5bee59807bf04deaab0a8eccecd5061528c< 6d4514ca9cdf61fec4ec634cf50386f6f7e69748 affected
… +22 more rows
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I. Basic Information for CVE-2026-74658

Vulnerability Information
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Vulnerability Title
futex: Prevent robust futex exit race some more
Source: CVE Program / CVE List V5
Vulnerability Description
In the Linux kernel, the following vulnerability has been resolved: futex: Prevent robust futex exit race some more A robust futex unlock stores 0 over the whole futex value - wiping FUTEX_WAITERS - and wakes a single waiter. That wakeup is a one-shot notification: the protocol relies on its recipient to either acquire the futex (and eventually unlock while aware of the remaining contention) or re-arm FUTEX_WAITERS before sleeping again. If the woken waiter is killed before it can do either, the kernel must jump in and wake the next task down the line. This is a known complication of the futex protocol with a previous partial fix in commit ca16d5bee598 ("futex: Prevent robust futex exit race"). Unfortunately, that fix is insufficient. If a third task re-acquired the futex through the uncontended fast path in the meantime, the notification is lost: robust exit processing sees that it is owned by another task and does nothing, while the new owner sees no FUTEX_WAITERS when it unlocks and wakes nobody. The remaining waiters sleep forever behind a free futex: A owns the futex, B and C sleep in FUTEX_WAIT uval == A | FUTEX_WAITERS A robust unlock: store 0, FUTEX_WAKE(1) wakes B uval == 0 D fast path acquire: cmpxchg(0 -> D) uval == D, no FUTEX_WAITERS B killed before acting on the wakeup B exit walk, pending op: owner D != B -> no action D unlock: no FUTEX_WAITERS -> no wake C sleeps forever This is clearly a shortcoming in the implementation, which fails to keep the FUTEX_WAITERS bit consistent. Work around this by augmenting the robust list exit processing to also perform the extra wakeup if the futex word is owned by another thread but FUTEX_WAITERS is not set. This does not fix the problem of a non-contended take over/release and free sequence, which has been discussed for years and has been addressed by commit 3ca9595d9fb6 ("futex: Add support for unlocking robust futexes") and subsequent changes, but failed to take the problem described above into account. A more complete solution which is based on the in kernel unlock of contended robust futexes has been discussed in the context of this change and should show up in mainline sooner than later. [ tglx: Amend change log slightly and fixup coding style ]
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 ca16d5bee59807bf04deaab0a8eccecd5061528c ~ 83b0f71d5a313a765754acab51d2ecc5de76e0b9 -
Linux Linux 5.5 -

II. Public POCs for CVE-2026-74658

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III. Intelligence Information for CVE-2026-74658

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Patches & Fixes for CVE-2026-74658 (7)

Same Patch Batch · Linux · 2026-08-22 · 150 CVEs total

CVE-2026-74705 10.0 CRITICAL udp: fix potential use-after-free in tunnel segmentation
CVE-2026-74612 10.0 CRITICAL veth: fix skb length accounting after XDP frag adjustment
CVE-2026-74588 9.8 CRITICAL sctp: keep chunk->transport in step with the list it is queued on
CVE-2026-74628 9.8 CRITICAL net/x25: fix use-after-free of the socket by its timers
CVE-2026-74669 9.8 CRITICAL ipvs: clear IPv4 options after rebasing tunnel ICMP errors
CVE-2026-74597 9.8 CRITICAL ip6_tunnel: clear skb2->cb[] in ip6ip6_err()
CVE-2026-74608 9.8 CRITICAL smb: client: Fix use-after-free in cifs_try_adding_channels()
CVE-2026-74662 9.8 CRITICAL inet: frags: publish queues before arming timer
CVE-2026-74611 9.8 CRITICAL tls: rx: restore msg_iter before TLS 1.3 optimistic retry
CVE-2026-74587 9.8 CRITICAL sctp: fix use-after-free of cached ASCONF chunk
CVE-2026-74688 9.8 CRITICAL sctp: clear control chunk transport if it is being removed
CVE-2026-74723 9.8 CRITICAL btrfs: lzo: reject inline extents without valid headers
CVE-2026-74616 9.8 CRITICAL xdp: reject clones that overrun skb_shared_info tailroom
CVE-2026-74591 9.8 CRITICAL mm/filemap: __filemap_add_folio() restore index before retrying
CVE-2026-74586 9.8 CRITICAL sctp: clear new_transport when removing a peer
CVE-2026-74727 9.8 CRITICAL ovpn: skip rehash for peers already removed from by_id
CVE-2026-74617 9.8 CRITICAL dibs: initialise dibs->lock in dibs_dev_alloc()
CVE-2026-74730 9.8 CRITICAL NFS: Pin the 'struct nfs_server' during a FREE_STATEID call
CVE-2026-74712 9.3 CRITICAL vdpa/mlx5: Fix buffer length in create_direct_keys()
CVE-2026-74665 9.1 CRITICAL net: fix skb length accounting after generic XDP frag adjustment

Showing top 20 of 150 CVEs. View all on vendor page &rarr; →

IV. Related Vulnerabilities

Same product: Linux
Same vendor: Linux

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