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NVD / CVE Program· CNA Linux

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

Noroxi assessment

Priority: Monitor (action score 30/100)

  • The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
  • Probability of exploitation in the next 30 days: 0.46% (FIRST EPSS).
  • Anyone who can reach it over the internet can trigger it. No account or password is required. No user action is required. No special conditions are required; it is repeatable.
  • According to CISA the attack is automatable: targets can be found by mass scanning.
  • Fixed version: Linux Linux 00633c4683828acd5256fa8d5163f440d74bbe71, 1bee417678f1135e35b25a37734db46aa94258d2, 20a93e397abe850c49b6fa0e8cc827b5f634a8f5.
  • Mentioned 1 time in Turkish national cyber security advisories (siberguvenlik.gov.tr).

Low priority for now. Upgrade to Linux Linux 00633c4683828acd5256fa8d5163f440d74bbe71, 1bee417678f1135e35b25a37734db46aa94258d2, 20a93e397abe850c49b6fa0e8cc827b5f634a8f5 or later.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · FIRST EPSS

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 ***

HighCVSS 7.5 · v3.1—No exploit Fix available
Published
Jun 24, 2026
Updated
Nov 10, 2026
EPSS
0.4% · 40th percentile

Report tools

JSON

Action score

30

Monitor

Low priority for now.

CVSS
30 / 40 · 7.5 / 10
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 0.4%

CISA SSVC decision

Exploitation
none
Automatable
yes
Technical impact
partial

Vulnrichment: CISA's decision-tree inputs.

CNA vs NVD score

NVD
—
CNA · Linux
7.5
NVD has not scored this yet; the score shown is the CNA’s.

The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.

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  • Not in KEV: no record of exploitation in the wild
  • No public exploit code on record
  • A fix has been released

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Follow CVE-2026-52946

When you'll hear from us

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  • when exploit code appears or is weaponized
  • when the record is updated (including a fixed version)
  • when EPSS rises 20 points in a week

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Noroxi analysis

What does it mean in your environment?

The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.

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Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

VendorProduct
linuxlinux kernel

Affected versions

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

  • linux linux kernel2.6.12.1 and later · before 5.10.259
  • linux linux kernel5.11 and later · before 5.15.210
  • linux linux kernel5.16 and later · before 6.1.176
  • linux linux kernel6.2 and later · before 6.6.143
  • linux linux kernel6.7 and later · before 6.12.94
  • linux linux kernel6.13 and later · before 6.18.36
  • linux linux kernel6.19 and later · before 7.0.13
  • linux linux kernel7.1 and later · before 7.1.1
  • linux linux kernel2.6.12

Versions reported by the vendor

Affected version ranges reported by the assigning authority (Linux). Independent of NVD's CPE analysis and usually ahead of it.

  • Linux Linux

    • 2.6.12affected
    • 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and later · before 54626335ea4174ab2d9a183b511d825f6765e47baffected · git
    • 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and later · before 897d6a7247739fb1528f98c575df4f2e5de7f994affected · git
    • 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and later · before 32dbd5ce4be3a3ed7e00f8af18795cc84fc50a33affected · git
    • 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and later · before b5fa9e32fb6718f70c986ee14dd5d01b4846f331affected · git
    • 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and later · before 1bee417678f1135e35b25a37734db46aa94258d2affected · git
    • 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and later · before 20a93e397abe850c49b6fa0e8cc827b5f634a8f5affected · git
    • 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and later · before bfcc8e8d8a495bb34cae9e620adfb75fb13a3954affected · git
    • 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and later · before 36c1b57b2ecf3c61ac93f5f07bd29b6f21e226edaffected · git
    • 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and later · before 00633c4683828acd5256fa8d5163f440d74bbe71affected · git

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

EcosystemPackageAffected rangeFix
Debian:12linuxbefore 6.1.176-16.1.176-1
Debian:13linuxbefore 6.12.94-16.12.94-1
Debian:14linuxbefore 7.0.13-17.0.13-1
openSUSE:Tumbleweedkernel-sourcebefore 7.1.2-1.17.1.2-1.1

Same product

linux: all records

Other highest-scoring records for the same primary product.

  • CVE-2026-31431crypto: algif_aead - Revert to operating out-of-placeKEV
    90Now
  • CVE-2022-0847A flaw was found in the way the "flags" member of the new pipe buffer structure was lacking proper initialization in copy_page_to_iter_pipe…KEV
    89Now
  • CVE-2021-22555Heap Out-Of-Bounds Write in Netfilter IP6T_SO_SET_REPLACEKEV
    85Now

Published before and after this one in the same product

  • ← EarlierCVE-2026-53130Jun 24, 2026 · fs/omfs: reject s_sys_blocksize smaller than OMFS_DIR_START
    31Monitor
  • ← EarlierCVE-2026-52945Jun 24, 2026 · Revert "wireguard: device: enable threaded NAPI"
    30Monitor
  • Later →CVE-2026-52947Jun 24, 2026 · net: qrtr: fix refcount saturation and potential UAF in qrtr_port_remove
    31Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / packageFixed versionSource
Linux Linux00633c4683828acd5256fa8d5163f440d74bbe71Vendor (CNA)
Linux Linux1bee417678f1135e35b25a37734db46aa94258d2Vendor (CNA)
Linux Linux20a93e397abe850c49b6fa0e8cc827b5f634a8f5Vendor (CNA)
Linux Linux32dbd5ce4be3a3ed7e00f8af18795cc84fc50a33Vendor (CNA)
Linux Linux36c1b57b2ecf3c61ac93f5f07bd29b6f21e226edVendor (CNA)
Linux Linux54626335ea4174ab2d9a183b511d825f6765e47bVendor (CNA)
Linux Linux897d6a7247739fb1528f98c575df4f2e5de7f994Vendor (CNA)
Linux Linuxb5fa9e32fb6718f70c986ee14dd5d01b4846f331Vendor (CNA)
Linux Linuxbfcc8e8d8a495bb34cae9e620adfb75fb13a3954Vendor (CNA)
debian:linux6.1.176-1 · Debian:12Package registry (OSV)
opensuse:kernel-source7.1.2-1.1 · openSUSE:TumbleweedPackage registry (OSV)

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

No dated events beyond publication.

No history yet (it accumulates with the daily EPSS job).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

No commit or PR link among the references.

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

No credits in the CNA record.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

No nightly-computed relations.

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

—

Bug bounty scope

No known public program.

Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).

National notice (Türkiye Cybersecurity Directorate / USOM)

Official security notices citing this record; remediation advice is on the agency's page.

All national notices →

Technical details

Attack conditions

  • Anyone who can reach it over the internet can trigger it.
  • No account or password is required.
  • No user action is required.
  • No special conditions are required; it is repeatable.

If successful

Confidentiality
none
Integrity
none
Availability
high · the service can be disrupted
Attack vector
Network
Attack complexity
Low
Privileges required
None
User interaction
None
Scope
Unchanged
Confidentiality impact
None
Integrity impact
None
Availability impact
High

Weakness class (CWE)

CWE-667 · Improper Locking

CVSS vector

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

nvd-secondary

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

Change log

  1. SSVC exploitation— → none
  2. Fix✗ → ✓

For records you follow, these changes also arrive as notifications. →

References

Show all references (11 more)

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records