CVE-2025-39946Public exploitNetwork attack vector

Remote code execution via repeated skb over-copy

Published Oct 4, 2025 · Updated Oct 4, 2025

Out-of-bounds write in the Linux kernel 6.0 through affected branches allows remote attackers to execute code via malformed TLS records. The tls_rx_msg_size path retries parsing a late-detected invalid record while each attempt copies more data into the already allocated skb. Reachability requires a kernel TLS receive socket, receive-buffer pressure, fragmented OOB header delivery, and a subsequent large send.

CVSS severity9.8
Critical
EPSS probability9.57%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Out-of-bounds write in the Linux kernel 6.0 through affected branches allows remote attackers to execute code via malformed TLS records. The tls_rx_msg_size path retries parsing a late-detected invalid record while each attempt copies more data into the already allocated skb. Reachability requires a kernel TLS receive socket, receive-buffer pressure, fragmented OOB header delivery, and a subsequent large send.

The record

CVE
CVE-2025-39946
Published
Oct 4, 2025
Updated
Oct 4, 2025
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
T1068
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Oct 4, 2025CVE publishedPublication date reported by the CVE source.
  2. Oct 4, 2025Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=6.0
  2. Affected versionversion=84c61fe1a75b4255df1e1e7c054c9e6d048da417 <0aeb54ac4cd5cf8f60131b4d9ec0b6dc9c27b20d
  3. Affected versionversion=84c61fe1a75b4255df1e1e7c054c9e6d048da417 <208640e6225cc929a05adbf79d1df558add3e231
  4. Affected versionversion=84c61fe1a75b4255df1e1e7c054c9e6d048da417 <4cefe5be73886f383639fe0850bb72d5b568a7b9
  5. Affected versionversion=84c61fe1a75b4255df1e1e7c054c9e6d048da417 <61ca2da5fb8f433ce8bbd1657c84a86272133e6b
  6. Affected versionversion=84c61fe1a75b4255df1e1e7c054c9e6d048da417 <b36462146d86b1f22e594fe4dae611dffacfb203

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=6.0; version=84c61fe1a75b4255df1e1e7c054c9e6d048da417 <0aeb54ac4cd5cf8f60131b4d9ec0b6dc9c27b20d; version=84c61fe1a75b4255df1e1e7c054c9e6d048da417 <208640e6225cc929a05adbf79d1df558add3e231; version=84c61fe1a75b4255df1e1e7c054c9e6d048da417 <4cefe5be73886f383639fe0850bb72d5b568a7b9; version=84c61fe1a75b4255df1e1e7c054c9e6d048da417 <61ca2da5fb8f433ce8bbd1657c84a86272133e6b; version=84c61fe1a75b4255df1e1e7c054c9e6d048da417 <b36462146d86b1f22e594fe4dae611dffacfb203

Published CVSS scores

7.0Amazon LinuxCVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
9.8Linux Kernel CVE TeamCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
7.0Oracle LinuxCVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

T1068Exploitation for Privilege Escalation

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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