CVE-2025-39682 affects Linux. Previdian lists 13 version rows; examples include 0 to < V5.0, 84c61fe1a75b4255df1e1e7c054c9e6d048da417 to < 2902c3ebcca52ca845c03182000e8d71d3a5196f, and 84c61fe1a75b4255df1e1e7c054c9e6d048da417 to < c09dd3773b5950e9cfb6c9b9a5f6e36d06c62677.

CVE-2025-39682 Exploitation Attempts Observed in the Wild — Linux

Q: Have exploitation attempts been observed?

Yes. Exploitation attempts have been reported for this vulnerability. Previdian lists it as a known exploited vulnerability. Listed in CISA KEV. Also reported by third-party sources. Confidence is confirmed.

Q: What should we do?

Prioritize remediation. Validate affected assets and apply vendor fixes on an accelerated timeline.

Decision summary

What security teams need to know first

Direct answers before the deeper technical record.

What it is

CVE-2025-39682 is an unauthenticated tls: fix handling of zero-length records on the rx_list affecting Linux.

Have exploitation attempts been observed?

Yes. Exploitation attempts have been reported for this vulnerability. Previdian lists it as a known exploited vulnerability. Listed in CISA KEV. Also reported by third-party sources. Confidence is confirmed.

Who is affected?

Linux, including affected before V5.0, affected before 2902c3ebcca52ca845c03182000e8d71d3a5196f, and affected before c09dd3773b5950e9cfb6c9b9a5f6e36d06c62677.

What should we do?

Prioritize remediation. Validate affected assets and apply vendor fixes on an accelerated timeline.

Overview

tls: fix handling of zero-length records on the rx_list

In the Linux kernel, the following vulnerability has been resolved:

tls: fix handling of zero-length records on the rx_list

Each recvmsg() call must process either - only contiguous DATA records (any number of them) - one non-DATA record

If the next record has different type than what has already been processed we break out of the main processing loop. If the record has already been decrypted (which may be the case for TLS 1.3 where we don't know type until decryption) we queue the pending record to the rx_list. Next recvmsg() will pick it up from there.

Queuing the skb to rx_list after zero-copy decrypt is not possible, since in that case we decrypted directly to the user space buffer, and we don't have an skb to queue (darg.skb points to the ciphertext skb for access to metadata like length).

Only data records are allowed zero-copy, and we break the processing loop after each non-data record. So we should never zero-copy and then find out that the record type has changed. The corner case we missed is when the initial record comes from rx_list, and it's zero length.

Vendor Product Affected Status

Siemens Affected

SIMATIC CN 4100

Before V5.0

Affected

Linux Affected

Linux

Before 2902c3ebcca52ca845c03182000e8d71d3a5196f Before c09dd3773b5950e9cfb6c9b9a5f6e36d06c62677 Before 3439c15ae91a517cf3c650ea15a8987699416ad9 Before 29c0ce3c8cdb6dc5d61139c937f34cb888a6f42e Before 62708b9452f8eb77513115b17c4f8d1a22ebf843 6.0

Affected

Linux Unaffected

Linux

Before 6.0 Through 6.1.* Through 6.6.* Through 6.12.* Through 6.16.* Through *

Unaffected

Published: 05 Sep 2025
Exploitation Attempts Reported: 18 Sep 2026
Attack vector: Remote
Complexity: Low
Privileges: None
User interaction: None

CVE References

CVE Record CVE.org · CVE Record https://www.cve.org/CVERecord?id=CVE-2025-39682
git.kernel.org/stable/c/2902c3ebcca52ca845c03182000e8d71d3a... git.kernel.org · CVE Record https://git.kernel.org/stable/c/2902c3ebcca52ca845c03182000e8d71d3a5196f
git.kernel.org/stable/c/c09dd3773b5950e9cfb6c9b9a5f6e36d06c... git.kernel.org · CVE Record https://git.kernel.org/stable/c/c09dd3773b5950e9cfb6c9b9a5f6e36d06c62677
git.kernel.org/stable/c/3439c15ae91a517cf3c650ea15a89876994... git.kernel.org · CVE Record https://git.kernel.org/stable/c/3439c15ae91a517cf3c650ea15a8987699416ad9
git.kernel.org/stable/c/29c0ce3c8cdb6dc5d61139c937f34cb888a... git.kernel.org · CVE Record https://git.kernel.org/stable/c/29c0ce3c8cdb6dc5d61139c937f34cb888a6f42e
git.kernel.org/stable/c/62708b9452f8eb77513115b17c4f8d1a22e... git.kernel.org · CVE Record https://git.kernel.org/stable/c/62708b9452f8eb77513115b17c4f8d1a22ebf843

Exploitation evidence

Evidence of exploitation attempts

Third-party attestation and first-party sensor observation are shown separately so teams can judge the evidence chain.

Exploitation Attempts Observed in the Wild

CISA

Recorded 18 Sep 2026

A trusted third party reported exploitation attempts.

Known exploited vulnerability sources

Per-source evidence links for KEV attestations are available through the Previdian Pro API.

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Source	Added
CISA First	2026-09-18 19:20 UTC
CVE	2026-09-18 19:40 UTC
The Hacker News	2026-09-19 00:00 UTC
BleepingComputer	2026-09-21 20:12 UTC

Detection

Operational artifacts and observed signals

Make the evidence actionable in scanner, SOC, and edge-control workflows.

Scanner coverage

No scanner integrations recorded yet.

Virtual patch status

No Previdian virtual patch is currently available. Future rules ship for ModSecurity, Cloudflare, and AWS WAF.

Learn about virtual patches →

No detection artifacts or sensor request patterns are available for this CVE yet.

Check back as sensor telemetry and scanner integrations are updated.

Risk and context

Severity, weaknesses, and research context

CVSS v3.1

9.8 Critical

Potential damage if exploited. Separate from whether attackers are using it.

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

EPSS

3.3%

Estimated chance of exploitation in the next 30 days. Previdian's warning comes from evidence, not this score.

Weaknesses

Improper Check for Unusual or Exceptional Conditions CWE-754

Recent mention · BleepingComputer

21 Sep 2026

CISA alerts of active exploitation of three Linux kernel flaws

The U.S. Cybersecurity and Infrastructure Security Agency (CISA) is warning that hackers are exploiting three Linux kernel vulnerabilities, one of them rated critical. [...]

Read full advisory

All Mentions

Recent mention · BleepingComputer

CISA alerts of active exploitation of three Linux kernel flaws

BleepingComputer · 21 Sep 2026

The U.S. Cybersecurity and Infrastructure Security Agency (CISA) is warning that hackers are exploiting three Linux kernel vulnerabilities, one of them rated critical. [...]

Recent mention · Security Affairs

U.S. CISA adds Linux Kernel flaws to its Known Exploited Vulnerabilities catalog

Security Affairs · 20 Sep 2026

U.S. Cybersecurity and Infrastructure Security Agency (CISA) adds Linux Kernel flaws to its Known Exploited Vulnerabilities catalog. The U.S. Cybersecurity and Infrastructure Security Agency (CISA) added [1, 2] the following vulnerabilities to its Known Exploited Vulnerabilities (KEV) catalog: Below are detailed descriptions of the flaws: At the time of this writing, there are currently no details on how the […]

Recent mention · The Hacker News

CISA Flags Three Linux Kernel Vulnerabilities Exploited in the Wild

The Hacker News · 19 Sep 2026

The U.S. Cybersecurity and Infrastructure Security Agency (CISA) on Friday added three security flaws impacting the Linux kernel to its Known Exploited Vulnerabilities (KEV) catalog, citing evidence of active exploitation. The vulnerabilities are listed below - CVE-2025-39682 (CVSS score: 9.8) - An improper check for unusual or exceptional conditions vulnerability in the TLS receive path

Timeline

From disclosure to observed exploitation attempts

21 Sep 2026
20:12 UTC

KEV confirmed by BleepingComputer

Exploitation attempts reported by an external source
19 Sep 2026
00:00 UTC

KEV confirmed by The Hacker News

Exploitation attempts reported by an external source
18 Sep 2026
19:40 UTC

KEV confirmed by CVE

Exploitation attempts reported by an external source
18 Sep 2026
19:20 UTC

Added to CISA KEV

Listed in the CISA Known Exploited Vulnerabilities catalog
05 Sep 2025
17:20 UTC

CVE published

Vulnerability disclosed publicly
16 Apr 2025
07:20 UTC

CVE ID reserved

Identifier reserved by the CNA

Pro API

Automate this intelligence

Confidence, exploit status, sensor telemetry, PoCs, scanner integrations, mentions, and tags are available programmatically for VM, SOC, and CTI workflows.

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Evidence confidence and provenance
First-party sensor telemetry
PoC and scanner references
Affected versions and enrichment
Automation-ready JSON delivery

GET /api/v2/pro/kevs/CVE-2025-39682

Sample API response

{
  "cve_id": "CVE-2025-39682",
  "confidence": "Confirmed",
  "cvss_score": 9.8,
  "cvss_estimated": false,
  "epss_score": 0.03312,
  "exploit_status": {
    "exploited_in_the_wild": true,
    "active_exploitation_observed": false
  },
  "sensor_telemetry": { "attempts": 0, "sensors": 0 }
}

CVE-2025-39682

tls: fix handling of zero-length records on the rx_list

Tags

CVE References

Exploitation Attempts Observed in the Wild

Known exploited vulnerability sources

Scanner coverage

Virtual patch status

Weaknesses

CISA alerts of active exploitation of three Linux kernel flaws

All Mentions

KEV confirmed by BleepingComputer

KEV confirmed by The Hacker News

KEV confirmed by CVE

Added to CISA KEV

CVE published

CVE ID reserved

Automate this intelligence