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CVE-2026-31555— futex: Clear stale exiting pointer in futex_lock_pi() retry path

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基金会的开源操作系统Linux所使用的内核。 Linux kernel存在安全漏洞，该漏洞源于futex_lock_pi重试路径中未清除过期的exiting指针，可能导致释放后重用。

AI Predicted 5.5 Difficulty: Moderate EPSS 0.17% · P6

Possible ATT&CK Techniques 1 AI

T1068 · Exploitation for Privilege Escalation

Affected Version Matrix 28

VendorProduct Version RangeStatus
Linux Linux 3ef240eaff36b8119ac9e2ea17cbf41179c930ba< 33095ae3bdde5e5c264d7e88a2f3e7703a26c7aa affected
3ef240eaff36b8119ac9e2ea17cbf41179c930ba< e7824ec168d2ac883a213cd1f4d6cc0816002a85 affected
3ef240eaff36b8119ac9e2ea17cbf41179c930ba< 5e8e06bf8909e79b4acd950cf578cfc2f10bbefa affected
3ef240eaff36b8119ac9e2ea17cbf41179c930ba< de7c0c04ad868f2cee6671b11c0a6d20421af1da affected
3ef240eaff36b8119ac9e2ea17cbf41179c930ba< 7475dfad10a05a5bfadebf5f2499bd61b19ed293 affected
3ef240eaff36b8119ac9e2ea17cbf41179c930ba< 92e47ad03e03dbb5515bdf06444bf6b1e147310d affected
3ef240eaff36b8119ac9e2ea17cbf41179c930ba< 71112e62807d1925dc3ae6188b11f8cfc85aec23 affected
3ef240eaff36b8119ac9e2ea17cbf41179c930ba< 210d36d892de5195e6766c45519dfb1e65f3eb83 affected
… +20 more rows
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I. Basic Information for CVE-2026-31555

Vulnerability Information
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Vulnerability Title
futex: Clear stale exiting pointer in futex_lock_pi() retry path
Source: CVE Program / CVE List V5
Vulnerability Description
In the Linux kernel, the following vulnerability has been resolved: futex: Clear stale exiting pointer in futex_lock_pi() retry path Fuzzying/stressing futexes triggered: WARNING: kernel/futex/core.c:825 at wait_for_owner_exiting+0x7a/0x80, CPU#11: futex_lock_pi_s/524 When futex_lock_pi_atomic() sees the owner is exiting, it returns -EBUSY and stores a refcounted task pointer in 'exiting'. After wait_for_owner_exiting() consumes that reference, the local pointer is never reset to nil. Upon a retry, if futex_lock_pi_atomic() returns a different error, the bogus pointer is passed to wait_for_owner_exiting(). CPU0 CPU1 CPU2 futex_lock_pi(uaddr) // acquires the PI futex exit() futex_cleanup_begin() futex_state = EXITING; futex_lock_pi(uaddr) futex_lock_pi_atomic() attach_to_pi_owner() // observes EXITING *exiting = owner; // takes ref return -EBUSY wait_for_owner_exiting(-EBUSY, owner) put_task_struct(); // drops ref // exiting still points to owner goto retry; futex_lock_pi_atomic() lock_pi_update_atomic() cmpxchg(uaddr) *uaddr ^= WAITERS // whatever // value changed return -EAGAIN; wait_for_owner_exiting(-EAGAIN, exiting) // stale WARN_ON_ONCE(exiting) Fix this by resetting upon retry, essentially aligning it with requeue_pi.
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
Vulnerability Title
Linux kernel 安全漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Linux kernel是美国Linux基金会的开源操作系统Linux所使用的内核。 Linux kernel存在安全漏洞，该漏洞源于futex_lock_pi重试路径中未清除过期的exiting指针，可能导致释放后重用。
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 3ef240eaff36b8119ac9e2ea17cbf41179c930ba ~ 33095ae3bdde5e5c264d7e88a2f3e7703a26c7aa -
Linux Linux 5.5 -

II. Public POCs for CVE-2026-31555

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III. Intelligence Information for CVE-2026-31555

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Same Patch Batch · Linux · 2026-04-24 · 138 CVEs total

CVE-2026-31609 9.8 CRITICAL smb: client: avoid double-free in smbd_free_send_io() after smbd_send_batch_flush()
CVE-2026-31657 9.8 CRITICAL batman-adv: hold claim backbone gateways by reference
CVE-2026-31633 9.8 CRITICAL rxrpc: Fix integer overflow in rxgk_verify_response()
CVE-2026-31608 9.8 CRITICAL smb: server: avoid double-free in smb_direct_free_sendmsg after smb_direct_flush_send_list
CVE-2026-31669 9.8 CRITICAL mptcp: fix slab-use-after-free in __inet_lookup_established
CVE-2026-31668 9.8 CRITICAL seg6: separate dst_cache for input and output paths in seg6 lwtunnel
CVE-2026-31536 9.8 CRITICAL smb: server: let send_done handle a completion without IB_SEND_SIGNALED
CVE-2026-31659 9.8 CRITICAL batman-adv: reject oversized global TT response buffers
CVE-2026-31649 9.8 CRITICAL net: stmmac: fix integer underflow in chain mode
CVE-2026-31607 9.8 CRITICAL usbip: validate number_of_packets in usbip_pack_ret_submit()
CVE-2026-31637 9.8 CRITICAL rxrpc: reject undecryptable rxkad response tickets
CVE-2026-31589 9.8 CRITICAL mm: call ->free_folio() directly in folio_unmap_invalidate()
CVE-2026-31636 9.1 CRITICAL rxrpc: fix RESPONSE authenticator parser OOB read
CVE-2026-31570 8.8 HIGH can: gw: fix OOB heap access in cgw_csum_crc8_rel()
CVE-2026-31558 8.8 HIGH LoongArch: KVM: Make kvm_get_vcpu_by_cpuid() more robust
CVE-2026-31588 8.8 HIGH KVM: x86: Use scratch field in MMIO fragment to hold small write values
CVE-2026-31553 8.8 HIGH KVM: arm64: Fix the descriptor address in __kvm_at_swap_desc()
CVE-2026-31622 8.8 HIGH NFC: digital: Bounds check NFC-A cascade depth in SDD response handler
CVE-2026-31629 8.8 HIGH nfc: llcp: add missing return after LLCP_CLOSED checks
CVE-2026-31611 8.6 HIGH ksmbd: require 3 sub-authorities before reading sub_auth[2]

Showing top 20 of 138 CVEs. View all on vendor page &rarr; →

IV. Related Vulnerabilities

Same product: Linux
Same vendor: Linux

V. Comments for CVE-2026-31555

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