Medium

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

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.

Published Apr 24, 2026 · Updated Oct 14, 2026 · Sources: NIST National Vulnerability Database, CVE Program (cve.org) e CISA ADP, GitHub Security Advisories · CNA: Linux

Low

Who exploits it and how urgent it is

A 0–100 score combining confirmed exploitation, ransomware and APT use, public exploits, EPSS and severity.

No exploitation signal in the sources consulted so far.

How the score was calculated

EPSS 0.2% (30-day exploitation probability)+1
Technical severity (medium)+3

The score orders the patch queue; it does not replace your asset context (internet exposure, criticality, compensating controls).

Triage

Is it exploited, how likely is exploitation, what does it touch, and how severe do the sources call it.

Exploitation

Not confirmed

Not in CISA KEV — an absence of record, not proof it is unexploited.

EPSS FIRST

0.17%

ahead of 6% of scored CVEs · Oct 14, 2026

Affects

Linux

Linux and 1 more

CVSS base

5.5

Medium · 2 source(s)

Remediation

Fixes and mitigations documented by the sources — linked to the original advisory.

Documented patch — git.kernel.org (NIST National Vulnerability Database)
Documented patch — git.kernel.org (NIST National Vulnerability Database)
Documented patch — git.kernel.org (NIST National Vulnerability Database)
Documented patch — git.kernel.org (NIST National Vulnerability Database)
Documented patch — git.kernel.org (NIST National Vulnerability Database)
Documented patch — git.kernel.org (NIST National Vulnerability Database)
Documented patch — git.kernel.org (NIST National Vulnerability Database)
Documented patch — git.kernel.org (NIST National Vulnerability Database)

First 24 hours

Ordered from the record’s own fields — exposure first, because you cannot patch what you have not found. A rule-generated starting point.

Identify exposed assets running the affected vendor/product/version combinations (Linux Linux, Linux Linux Kernel).
Apply the fixed version or the patch documented under Remediation.
Search available logs for exploit probes, errors and authentication anomalies.

Affected scope

Vendor, product and versions as the sources word them.

Vendor	Product	Versions	Status	Source
Linux	Linux	version cf16e42709aa86aa3e37f3acc3d13d5715d90096≥ 3ef240eaff36b8119ac9e2ea17cbf41179c930ba and < 33095ae3bdde5e5c264d7e88a2f3e7703a26c7aa≥ 3ef240eaff36b8119ac9e2ea17cbf41179c930ba and < e7824ec168d2ac883a213cd1f4d6cc0816002a85≥ 3ef240eaff36b8119ac9e2ea17cbf41179c930ba and < 5e8e06bf8909e79b4acd950cf578cfc2f10bbefa≥ 3ef240eaff36b8119ac9e2ea17cbf41179c930ba and < de7c0c04ad868f2cee6671b11c0a6d20421af1da≥ 3ef240eaff36b8119ac9e2ea17cbf41179c930ba and < 7475dfad10a05a5bfadebf5f2499bd61b19ed293≥ 3ef240eaff36b8119ac9e2ea17cbf41179c930ba and < 92e47ad03e03dbb5515bdf06444bf6b1e147310d≥ 3ef240eaff36b8119ac9e2ea17cbf41179c930ba and < 71112e62807d1925dc3ae6188b11f8cfc85aec23 and 11 more ≥ 3ef240eaff36b8119ac9e2ea17cbf41179c930ba and < 210d36d892de5195e6766c45519dfb1e65f3eb83version f2a9957e5c08b1b1caacd18a3dc4c0a1bdb7b463version 61fa9f167caaa73d0a7c88f498eceeb12c6fa3dbversion 7874eee0130adf9bee28e8720bb5dd051089def3version fc3b55ef2c840bb2746b2d8121a0788de84f7fac≥ 4.4.255 and < 4.5≥ 4.9.255 and < 4.10≥ 4.14.158 and < 4.15≥ 4.19.172 and < 4.20≥ 5.4.1 and < 5.5version 5.5	Vulnerable	CVE Program (cve.org) e CISA ADP
Linux	Linux Kernel	version 7.0-rc7≥ 6.13 and < 6.18.21≥ 4.9.255 and < 4.10≥ 4.14.158 and < 4.15≥ 4.19.172 and < 4.20≥ 5.4.1 and < 5.5≥ 5.5.1 and < 5.10.253≥ 5.11 and < 5.15.203 and 12 more ≥ 5.16 and < 6.1.168≥ 6.2 and < 6.6.131≥ 6.7 and < 6.12.80≥ 4.4.255 and < 4.5≥ 6.19 and < 6.19.11version 5.5version 7.0-rc1version 7.0-rc2version 7.0-rc3version 7.0-rc4version 7.0-rc5version 7.0-rc6	Vulnerable	NIST National Vulnerability Database

Attack characteristics

The CVSS vector, decoded. It describes the attack, not your exposure to it.

Attack vector

Local

Attack complexity

Low

Privileges required

Low

User interaction

None

Scope

Unchanged

Confidentiality

None

Integrity

None

Availability

High

Every base score collected

Sources score independently and may disagree; each row says who scored it and under which version.

Score	Version	Severity	Expl.	Impact	Scored by
5.5	CVSS 3.1	Medium	1.8	3.6	nvd@nist.gov via NIST National Vulnerability Database
5.5	CVSS 3.1	Medium	—	—	GitHub, Inc. via GitHub Security Advisories

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H (score shown at the top: nvd@nist.gov)

EPSS over time FIRST

Oct 13, 2026 → Oct 14, 2026 · 2 reading(s) · max 0.17%

Detection

Read off the CVSS vector and the weakness class. Starting points, not tested rules.

Local/physical vector: focus on endpoint telemetry (EDR) from affected hosts.

endpoint telemetry (EDR)

Timeline

What happened to this CVE, newest first.

2026
Affected products added · linux/linux
Oct 13, 2026 · CVE Program (cve.org) e CISA ADP
Record published
Oct 13, 2026
Fix documented
Oct 13, 2026 · NIST National Vulnerability Database
CVSS changed · 5.5
Oct 13, 2026 · NIST National Vulnerability Database
Source status changed · → Modified
Oct 13, 2026 · NIST National Vulnerability Database
Record created in this database
Oct 13, 2026 · NIST National Vulnerability Database
CVE published
Apr 24, 2026 · Linux

Source activity

Repeated readings are counted rather than listed.

2× References added · Oct 14, 2026 – Oct 14, 2026
1× Official description updated · Oct 13, 2026 – Oct 13, 2026

References

13 on the record

git.kernel.org/stable/c/210d36d892de5195e6766c45519dfb1e65f3eb83
Patch, NIST National Vulnerability Database
git.kernel.org/stable/c/71112e62807d1925dc3ae6188b11f8cfc85aec23
Patch, NIST National Vulnerability Database
git.kernel.org/stable/c/e7824ec168d2ac883a213cd1f4d6cc0816002a85
Patch, NIST National Vulnerability Database
git.kernel.org/stable/c/7475dfad10a05a5bfadebf5f2499bd61b19ed293
Patch, NIST National Vulnerability Database
git.kernel.org/stable/c/92e47ad03e03dbb5515bdf06444bf6b1e147310d
Patch, NIST National Vulnerability Database
git.kernel.org/stable/c/5e8e06bf8909e79b4acd950cf578cfc2f10bbefa
Patch, NIST National Vulnerability Database
git.kernel.org/stable/c/33095ae3bdde5e5c264d7e88a2f3e7703a26c7aa
Patch, NIST National Vulnerability Database
git.kernel.org/stable/c/de7c0c04ad868f2cee6671b11c0a6d20421af1da
Patch, NIST National Vulnerability Database
nvd.nist.gov/vuln/detail/CVE-2026-31555
GitHub Security Advisories
cert-portal.siemens.com/productcert/html/ssa-082556.html
NIST National Vulnerability Database
cert-portal.siemens.com/productcert/html/ssa-457936.html
NIST National Vulnerability Database
cert-portal.siemens.com/productcert/html/ssa-019113.html
NIST National Vulnerability Database
github.com/advisories/GHSA-58x2-94x2-vr83
GitHub Security Advisories

Elsewhere on this site

Linux
every CVE for this vendor

Related CVEs (same products)

Critical CVE-2026-99999 ipv4: validate checksum_start before completing checksum 13h
Unknown CVE-2026-98432 ipv4: free inet_opt and ireq_opt after an RCU grace period 13h
Unknown CVE-2026-98426 wifi: mwifiex: fix IRQ leak using wrong index in MSI-X error path 1d
Unknown CVE-2026-98427 net/sched: codel: bound the dropping loop per dequeue call 1d
Unknown CVE-2026-98428 ALSA: usb: 6fire: Avoid embedded URBs 1d
Unknown CVE-2026-98429 RDMA/efa: Keep EQ resources alive while IRQ is registered 1d

Not in any source we poll

Listed rather than left blank: an empty field and an unmeasured one look identical on screen, and only one is a reason to look elsewhere.

No CISA SSVC assessment.
No CWE classification.
No confirmed IOCs, IP addresses, domains, file hashes, or malware artifacts supplied.
No organization-specific asset inventory, compensating-control status, or patch deployment evidence supplied.
No exploit packet captures, log samples, or incident case IDs supplied.

Answered from this record

Text assembled only from the fields above — no additional claims.

What should defenders know first?

CVE-2026-31555 is "futex: Clear stale exiting pointer in futex_lock_pi() retry path", rated Medium. It affects Linux (Linux); versions are in the scope table. It is not in CISA KEV, which does not rule out exploitation. CVSS 5.5 describes technical severity. EPSS 0.17% estimates the probability of exploitation in 30 days; neither replaces your asset context. First verify whether exposed or business-critical assets run the affected versions, apply vendor fixes or mitigations, and preserve logs for review.

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