VulnerabilityPublished 24 Jun 2026Updated 15 Oct 2026

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

Source GCVE Database

Authoritative record:CVE-2026-52946· High 7.5

Not known to be exploited · CVSS 7.5 High · fixed in bfcc8e8d8a495bb34cae9e620adfb75fb13a3954 : patch Linux kernel soon.

Data as of 26 Oct 2026, 17:16 UTC

CVSS 3.1 base score

7.5High

How severe the flaw is on the 0–10 CVSS scale.

EPSS: 0.4% chance of exploitation in 30 days – higher than 40% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in bfcc8e8d8a495bb34cae9e620adfb75fb13a3954, b5fa9e32fb6718f70c986ee14dd5d01b4846f331, 54626335ea4174ab2d9a183b511d825f6765e47b +6

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Attack Vector: Network
Attack Complexity: Low
Privileges Required: None
User Interaction: None
Scope: Unchanged
Confidentiality: None
Integrity: None
Availability: High

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Network: The vulnerable component is bound to the network stack and the set of possible attackers extends beyond the other options listed, up to and including the entire Internet. Such a vulnerability is often termed 'remotely exploitable' and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers).
Attack Complexity: Low: Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success against the vulnerable component.
Privileges Required: None: The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files to carry out an attack.
User Interaction: None: The vulnerable system can be exploited without any interaction from any user.
Scope: Unchanged: An exploited vulnerability can only affect resources managed by the same security authority. In this case, the vulnerable component and the impacted component are either the same, or both are managed by the same security authority.
Confidentiality: None: There is no loss of confidentiality within the impacted component.
Integrity: None: There is no loss of integrity within the impacted component.
Availability: High: There is total loss of availability, resulting in the attacker being able to fully deny access to resources in the impacted component; this loss is either sustained (while the attacker continues to deliver the attack) or persistent (the condition persists even after the attack has completed). Alternatively, the attacker has the ability to deny some availability, but the loss of availability presents a direct, serious consequence to the impacted component (e.g., the attacker cannot disrupt existing connections, but can prevent new connections; the attacker can repeatedly exploit a vulnerability that, in each instance of a successful attack, leaks a only small amount of memory, but after repeated exploitation causes a service to become completely unavailable).

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 24 Jun 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponised: Public exploit code exists in Metasploit or Exploit-DB, or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Upgrade to a fixed release listed under Affected software.

Affected software

Product	Affected	Fixed in
LinuxLinux	Affected ≥ 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, < bfcc8e8d8a495bb34cae9e620adfb75fb13a3954	Fixed in bfcc8e8d8a495bb34cae9e620adfb75fb13a3954
LinuxLinux	Affected ≥ 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, < b5fa9e32fb6718f70c986ee14dd5d01b4846f331	Fixed in b5fa9e32fb6718f70c986ee14dd5d01b4846f331
LinuxLinux	Affected ≥ 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, < 54626335ea4174ab2d9a183b511d825f6765e47b	Fixed in 54626335ea4174ab2d9a183b511d825f6765e47b
LinuxLinux	Affected ≥ 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, < 897d6a7247739fb1528f98c575df4f2e5de7f994	Fixed in 897d6a7247739fb1528f98c575df4f2e5de7f994
LinuxLinux	Affected ≥ 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, < 00633c4683828acd5256fa8d5163f440d74bbe71	Fixed in 00633c4683828acd5256fa8d5163f440d74bbe71
LinuxLinux	Affected ≥ 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, < 36c1b57b2ecf3c61ac93f5f07bd29b6f21e226ed	Fixed in 36c1b57b2ecf3c61ac93f5f07bd29b6f21e226ed

AI-suggested

A fix is available that replaces the read_lock(&tasklist_lock) with rcu_read_lock() in the affected code paths. Users should apply the official Linux kernel updates that include this fix. Since this is a kernel-level vulnerability, updating to a patched kernel version is the recommended remediation. Patch status is not explicitly confirmed in the provided data; users should check the vendor or Linux kernel advisories for the specific patched versions and apply updates accordingly.

Description

A deadlock vulnerability in the Linux kernel's fs/fcntl subsystem related to SOFTIRQ-unsafe lock order in fasync signaling has been fixed. The issue occurs when process groups receive signals via send_sigio() or send_sigurg(), which are called from softirq context and attempt to acquire read_lock(&tasklist_lock), potentially causing a deadlock due to the rwlock writer fairness mechanism. The fix replaces the read_lock on tasklist_lock with rcu_read_lock(), aligning with existing RCU protections and mitigating a potential remote denial of service via TCP URG packets.

Impact

The vulnerability can cause a deadlock in the Linux kernel, resulting in a denial of service condition. This can be triggered remotely via TCP URG packets, potentially impacting system availability. There is no impact on confidentiality or integrity. The CVSS v3.1 score is 7.5 (high severity) with network attack vector, low attack complexity, no privileges required, no user interaction, and impact limited to availability.

CWE-667Improper Locking (opens in a new tab)
Class weakness
The product does not properly acquire or release a lock on a resource, leading to unexpected resource state changes and behaviors.
Implementation · Libraries or Frameworks
Use industry standard APIs to implement locking mechanism.
Attack patterns
Leveraging Race Conditions via Symbolic Links (opens in a new tab)
Forced Deadlock (opens in a new tab)
Leveraging Race Conditions (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).
CWE-362Concurrent Execution using Shared Resource with Improper Synchronization ('Race Condition') (opens in a new tab)
Class weaknessLikelihood of exploit: MediumOWASP Top 10 A06:2025: Insecure Design (opens in a new tab)
The product contains a concurrent code sequence that requires temporary, exclusive access to a shared resource, but a timing window exists in which the shared resource can be modified by another code sequence operating concurrently.
Architecture and Design
In languages that support it, use synchronization primitives. Only wrap these around critical code to minimize the impact on performance.
Architecture and Design
Use thread-safe capabilities such as the data access abstraction in Spring.
Architecture and Design
Minimize the usage of shared resources in order to remove as much complexity as possible from the control flow and to reduce the likelihood of unexpected conditions occurring.
OWASP Cheat Sheets
Abuse Case (opens in a new tab)
Secure Design Principles (opens in a new tab)
OWASP ASVS 4.0.3
V1.11.2 (opens in a new tab)
Attack patterns
Leveraging Time-of-Check and Time-of-Use (TOCTOU) Race Conditions (opens in a new tab)
Leveraging Race Conditions (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

References

Community reviews

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 8 Sep 2026, 14:38 UTC

WeaknessesCWE-667, CWE-362

Technical details

References

Community reviews

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