VulnerabilityPublished 11 Sep 2025Updated 10 Nov 2026

CVE-2025-39756: Linux kernel · fs: Prevent file descriptor table allocations exceeding INT_MAX

Affects Linux kernelSource CVE Database V5

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Not known to be exploited · fixed in f95638a8f22eba307dceddf5aef9ae2326bbcf98 : update Linux kernel when convenient.

Data as of 10 Nov 2026, 12:50 UTC

Severity

Medium

Rated Medium by Threat Radar's AI analysis · No CVSS score from NVD or the CNA

Thin evidence

One scorer or none

Patch: Available – fixed in f95638a8f22eba307dceddf5aef9ae2326bbcf98, dfd1f4ea98c3bd3a03d12169b5b2daa1f0a3e4ae, d4f9351243c17865a8cdbe6b3ccd09d0b13a7bcc +6

Exploitation evidence

Disclosed: evidence found.
CVE published 11 Sep 2025
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: 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 10 Nov 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.
Weaponized: A Metasploit exploit module or Exploit-DB entry exists (Metasploit scanner modules do not count), 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 ≥ 9cfe015aa424b3c003baba3841a60dd9b5ad319b, < f95638a8f22eba307dceddf5aef9ae2326bbcf98	Fixed in f95638a8f22eba307dceddf5aef9ae2326bbcf98
LinuxLinux	Affected ≥ 9cfe015aa424b3c003baba3841a60dd9b5ad319b, < dfd1f4ea98c3bd3a03d12169b5b2daa1f0a3e4ae	Fixed in dfd1f4ea98c3bd3a03d12169b5b2daa1f0a3e4ae
LinuxLinux	Affected ≥ 9cfe015aa424b3c003baba3841a60dd9b5ad319b, < d4f9351243c17865a8cdbe6b3ccd09d0b13a7bcc	Fixed in d4f9351243c17865a8cdbe6b3ccd09d0b13a7bcc
LinuxLinux	Affected ≥ 9cfe015aa424b3c003baba3841a60dd9b5ad319b, < b4159c5a90c03f8acd3de345a7f5fc63b0909818	Fixed in b4159c5a90c03f8acd3de345a7f5fc63b0909818
LinuxLinux	Affected ≥ 9cfe015aa424b3c003baba3841a60dd9b5ad319b, < 749528086620f8012b83ae032a80f6ffa80c45cd	Fixed in 749528086620f8012b83ae032a80f6ffa80c45cd
LinuxLinux	Affected ≥ 9cfe015aa424b3c003baba3841a60dd9b5ad319b, < 628fc28f42d979f36dbf75a6129ac7730e30c04e	Fixed in 628fc28f42d979f36dbf75a6129ac7730e30c04e

AI-suggested

A fix is available and has been applied in multiple Linux kernel commits. The fix adds a check in alloc_fdtable() to prevent allocation requests exceeding INT_MAX, causing the operation to fail gracefully with -EMFILE. Systems should update to a kernel version that includes these fixes to avoid kernel warnings and excessive memory allocation attempts when using high file descriptor limits.

Description

CVE-2025-39756 is a vulnerability in the Linux kernel where setting the file descriptor limit (fs.nr_open) to a very high value can cause the kernel to attempt massive memory allocations exceeding INT_MAX. This leads to kernel warnings and impractical allocation requests over 8GB, triggered when processes use file descriptors near this limit. The issue arises from systemd increasing fs.nr_open to near 1 billion descriptors without accounting for kernel allocation limits. The vulnerability is fixed by adding a check to prevent allocations exceeding INT_MAX, causing operations to fail gracefully instead of triggering warnings and large allocations.

Impact

The vulnerability causes the Linux kernel to attempt impractical and excessive memory allocations (>8GB) when processes use file descriptors near the very high fs.nr_open limit set by systemd. This results in kernel warnings and potential instability due to failed large memory allocations. Normal system operation is unlikely to reach these limits, but certain tests and programs that stress file descriptor limits can trigger this issue. There is no indication of remote exploitation or code execution, but the kernel warning and failed allocations can disrupt testing or specialized workloads.

References

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 10 Nov 2026, 12:50 UTC

Technical details

References

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