CVE Intelligence
High

CVE-2026-52946 — fs/fcntl: fix SOFTIRQ-unsafe lock order in fasync signaling

In the Linux kernel, the following vulnerability has been resolved: fs/fcntl: fix SOFTIRQ-unsafe lock order in fasync signaling A SOFTIRQ-safe to SOFTIRQ-unsafe lock order deadlock can occur in send_sigio() and send_sigurg() when a process group receives a signal. When FASYNC is configured for a process group (PIDTYPE_PGID), both functions use read_lock(&tasklist_lock) to traverse the task list. However, they are frequently called from softirq context: - send_sigio() via input_inject_event -> kill_fasync - send_sigurg() via tcp_check_urg -> sk_send_sigurg (NET_RX_SOFTIRQ) The deadlock is caused by the rwlock writer fairness mechanism: 1. CPU 0 (process context) holds read_lock(&tasklist_lock) in do_wait(). 2. CPU 1 (process context) attempts write_lock(&tasklist_lock) in fork() or exit() and spins, which blocks all new readers. 3. CPU 0 is interrupted by a softirq (e.g., TCP URG packet reception). 4. The softirq calls send_sigurg() and attempts to acquire read_lock(&tasklist_lock), deadlocking because CPU 1 is waiting. Since PID hashing and do_each_pid_task() traversals are already RCU-protected, the read_lock on tasklist_lock is no longer strictly required for safe traversal. Fix this by replacing tasklist_lock with rcu_read_lock(), aligning the process group signaling path with the single-PID path. This also mitigates a potential remote denial of service vector via TCP URG packets. Lockdep splat: ===================================================== WARNING: SOFTIRQ-safe -> SOFTIRQ-unsafe lock order detected [...] Chain exists of: &dev->event_lock --> &f_owner->lock --> tasklist_lock Possible interrupt unsafe locking scenario: CPU0 CPU1 ---- ---- lock(tasklist_lock); local_irq_disable(); lock(&dev->event_lock); lock(&f_owner->lock); <Interrupt> lock(&dev->event_lock); *** DEADLOCK ***

Published Jun 24, 2026 · Updated Oct 15, 2026 · Sources: NIST National Vulnerability Database, CVE Program (cve.org) e CISA ADP, GitHub Security Advisories · CNA: Linux

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 0.5% (30-day exploitation probability)+6
  • Technical severity (high)+6

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
0.47%
ahead of 39% of scored CVEs · Oct 15, 2026
Affects
Linux
Linux and 1 more
CVSS base
7.5
High · 3 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)
  • 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.

  1. Identify exposed assets running the affected vendor/product/version combinations (Linux Linux, Linux Linux Kernel).
  2. The attack is network-based and needs no privileges: restrict exposure (ACLs, VPN, WAF) until patched.
  3. Apply the fixed version or the patch documented under Remediation.
  4. Search available logs for exploit probes, errors and authentication anomalies.

Affected scope

Vendor, product and versions as the sources word them.

VendorProductVersionsStatusSource
Linux Linux version 2.6.12≥ 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and < 00633c4683828acd5256fa8d5163f440d74bbe71≥ 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and < 36c1b57b2ecf3c61ac93f5f07bd29b6f21e226ed≥ 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and < bfcc8e8d8a495bb34cae9e620adfb75fb13a3954≥ 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and < 20a93e397abe850c49b6fa0e8cc827b5f634a8f5≥ 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and < 1bee417678f1135e35b25a37734db46aa94258d2≥ 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and < b5fa9e32fb6718f70c986ee14dd5d01b4846f331≥ 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and < 32dbd5ce4be3a3ed7e00f8af18795cc84fc50a33
and 2 more ≥ 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and < 897d6a7247739fb1528f98c575df4f2e5de7f994≥ 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and < 54626335ea4174ab2d9a183b511d825f6765e47b
Vulnerable CVE Program (cve.org) e CISA ADP
Linux Linux Kernel version 2.6.12-rc4version 2.6.12-rc5≥ 2.6.12.1 and < 5.10.259version 2.6.12-rc3version 2.6.12-rc2version 2.6.12≥ 7.1 and < 7.1.1≥ 6.19 and < 7.0.13
and 5 more ≥ 6.13 and < 6.18.36≥ 6.7 and < 6.12.94≥ 6.2 and < 6.6.143≥ 5.16 and < 6.1.176≥ 5.11 and < 5.15.210
Vulnerable NIST National Vulnerability Database

Attack characteristics

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

Attack vector
Network
Attack complexity
Low
Privileges required
None
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.

ScoreVersionSeverityExpl.ImpactScored by
7.5 CVSS 3.1 High 3.9 3.6 416baaa9-dc9f-4396-8d5f-8c081fb06d67 via NIST National Vulnerability Database
7.5 CVSS 3.1 High — — GitHub, Inc. via GitHub Security Advisories
7.5 CVSS 3.1 High — — Linux via CVE Program (cve.org) e CISA ADP
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H (score shown at the top: 416baaa9-dc9f-4396-8d5f-8c081fb06d67)

Weakness MITRE

Weakness class according to MITRE’s CWE catalog.

CWE-667

Other CVEs with this weakness →

EPSS over time FIRST

Oct 13, 2026 → Oct 15, 2026 · 3 reading(s) · max 0.47%

Detection

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

  • Prioritize edge telemetry for the network-reachable component (proxy, WAF, IDS/IPS).
web/proxy/WAF logsnetwork IDS/IPS

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 · 7.5
    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
    Jun 24, 2026 · Linux

Source activity

Repeated readings are counted rather than listed.

  • 2× References added · Oct 14, 2026 – Oct 15, 2026
  • 1× Official description updated · Oct 13, 2026 – Oct 13, 2026

References

14 on the record

Elsewhere on this site

Linux
every CVE for this vendor
CWE-667
other pages naming this weakness

Related CVEs (same products)

  • CVE-2026-99999 ipv4: validate checksum_start before completing checksum 1d
  • CVE-2026-98432 ipv4: free inet_opt and ireq_opt after an RCU grace period 1d
  • CVE-2026-98424 wifi: cfg80211: undo netns switch if renaming the wiphy fails 2d
  • CVE-2026-98425 wifi: mac80211: don't warn when an IBSS has no channel to scan 2d
  • CVE-2026-98426 wifi: mwifiex: fix IRQ leak using wrong index in MSI-X error path 2d
  • CVE-2026-98427 net/sched: codel: bound the dropping loop per dequeue call 2d

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 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-2026-52946 is "fs/fcntl: fix SOFTIRQ-unsafe lock order in fasync signaling", rated High. It affects Linux (Linux); versions are in the scope table. It is not in CISA KEV, which does not rule out exploitation. CVSS 7.5 describes technical severity. EPSS 0.47% 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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