What is CVE-2025-39682?

CVE-2025-39682 is tls: fix handling of zero-length records on the rx_list. The supplied enrichment data classifies it as Unclassified mapped to CWE-754 CWE-754.

Which versions are affected?

Affected product and version evidence is listed in the product table above. Current public advisories should be checked for exact version scope before patch targeting is finalized.

Is there active exploitation?

Yes: CISA KEV signal present. If exploitation is not confirmed from current sources, teams should document that status and continue monitoring KEV, vendor, and telemetry updates.

Is there a public exploit?

7 public PoC repositories reported; 1 marked weaponized in current dataset. Public exploit or PoC availability should raise triage priority, especially for exposed or business-critical systems.

How can defenders detect it?

Start with web/proxy/WAF logs, application logs, network IDS/IPS where available. Look for vulnerability-class behavior, product errors, suspicious authentication events, exploit probes, and abnormal process activity based only on evidence that applies to the affected product.

How should teams prioritize it?

Prioritize CVE-2025-39682 using CVSS 9.8, EPSS 3%, KEV status, public PoC status, and asset exposure. Internet-facing, privileged, or business-critical deployments should be handled first.

Are workarounds available?

The supplied mitigation guidance says to apply vendor patches and restrict external exposure until fixed. Fixed-version evidence is listed in the mitigation section above.

Which threat actors are linked publicly?

No public threat actor linkage is confirmed from current sources. Do not attribute exploitation to a threat actor unless the source evidence explicitly supports that linkage.

What should be done in the next 24 hours?

Identify exposed assets running affected vendor/product/version combinations. Treat as emergency remediation because CISA KEV status is present. Search available logs for exploit probes, errors, authentication anomalies, or suspicious child processes matching the vulnerability class. Open remediation tickets with affected assets, owners, evidence status, and detection coverage so decisions are traceable.

CISA KEVcriticalpublic exploit

CVE-2025-39682

CVE-2025-39682 — tls: fix handling of zero-length records on the rx_list

Q: Is it in CISA KEV?

Yes. The supplied enrichment data lists CVE-2025-39682 in CISA KEV with required action: Apply mitigations in accordance with vendor instructions, ensuring compliance with CISA’s BOD 26-04 Prioritizing Security Updates Based on Risk (see URL in Notes) guidance and CISA’s “Forensics Triage Requirements” (see URL in Notes). Follow applicable BOD 26-04 guidance for cloud services or discontinue use of the product if mitigations are unavailable. Stakeholders are responsible for evaluating each asset's internet exposure and ensuring adherence to BOD 26-04 patching guidelines.. KEV status should be monitored because it can change after initial disclosure or after exploitation becomes publicly confirmed.

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.

Published Sep 5, 2025Updated Sep 21, 2026Sources: NVD, Linux (CNA), CISA, FIRST EPSS, GitHub, GitHub Security Advisory, Microsoft MSRC, Red Hat (VEX), SOCRadar CTI

Triage

Is it exploited, how likely is exploitation, what does it touch, and how severe do the scoring sources call it.

Exploitation

Confirmed

CISA KEV, listed Sep 18, 2026

EPSS

ahead of 86% of scored CVEs

Affects

Linux

14 products listed

CVSS base

9.8

critical · 4 sources

CISA SSVC assessment

Three decision points CISA publishes for the CVEs it assesses · SSVC 2.0.3. A stakeholder decision, not a severity score.

CISA

Exploitation

Active

none · proof-of-concept · active

Automatable

Yes

can an attacker script all four kill-chain steps

Technical impact

Total

partial · total control of the vulnerable component

Remediation

The vendor's own words where we have them.

Upgrade Linux to a fixed release (0 to < 6.0). Apply vendor patches per advisory and restrict external exposure of the affected component until patched.

CISA required action

Apply mitigations in accordance with vendor instructions, ensuring compliance with CISA’s BOD 26-04 Prioritizing Security Updates Based on Risk (see URL in Notes) guidance and CISA’s “Forensics Triage Requirements” (see URL in Notes). Follow applicable BOD 26-04 guidance for cloud services or discontinue use of the product if mitigations are unavailable. Stakeholders are responsible for evaluating each asset's internet exposure and ensuring adherence to BOD 26-04 patching guidelines.

Federal deadline Sep 21, 2026 — passed 17 days ago

Red Hat VEX · CVE-2025-39682

fixed1092affected0not affected90

vendor_fix: For details on how to apply this update, which includes the changes described in this advisory, refer to: https://access.redhat.com/articles/11258 The system must be rebooted for …

First 24 hours

Ordered from the record's own fields — exposure first, because you cannot patch what you have not found.

Identify exposed assets running affected vendor/product/version combinations.
Treat as emergency remediation because CISA KEV status is present.
Search available logs for exploit probes, errors, authentication anomalies, or suspicious child processes matching the vulnerability class.

Affected scope

Vendor, product and version as the advisories word them.

Vendor	Product	Versions	Status
Linux	Linux	84c61fe1a75b4255df1e1e7c054c9e6d048da417 to < 2902c3ebcca52ca845c03182000e8d71d3a5196f	Vulnerable
Linux	Linux	84c61fe1a75b4255df1e1e7c054c9e6d048da417	Vulnerable
Linux	Linux	84c61fe1a75b4255df1e1e7c054c9e6d048da417 to < 3439c15ae91a517cf3c650ea15a8987699416ad9	Vulnerable
Linux	Linux	84c61fe1a75b4255df1e1e7c054c9e6d048da417 to < 29c0ce3c8cdb6dc5d61139c937f34cb888a6f42e	Vulnerable
Linux	Linux	84c61fe1a75b4255df1e1e7c054c9e6d048da417 to < 62708b9452f8eb77513115b17c4f8d1a22ebf843	Vulnerable
Linux	Linux	6.0	Vulnerable
Linux	Linux	0 to < 6.0	Patched
Linux	Linux	6.1.149 to <= 6.1.*	Patched
Linux	Linux	6.6.103 to <= 6.6.*	Patched
Linux	Linux	6.12.44 to <= 6.12.*	Patched
Linux	Linux	6.16.4 to <= 6.16.*	Patched
Linux	Linux	6.17	Patched

Attack characteristics

The CVSS vector, decoded. It describes the attack, not your exposure to it.

Availability

High

Confidentiality

High

Integrity

High

Scope

Unchanged

Attack Complexity

Low

Attack Vector

Network

Privileges Req

None

User Interaction

None

Every base score collected

Sources score independently and disagree; each row says who scored it and under which version.

Score	Version	Severity	Expl.	Impact	Source
9.8	CVSS 3.1	critical	3.9	5.9	CNA, NVD, Linux (CNA)
7.1	CVSS 3.1	high	—	—	GHSA
6.5	CVSS 3.1	medium	—	—	Microsoft
7	CVSS 3.1	high	—	—	Red Hat (VEX)

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

Weakness & attack patterns

CWE-754

CISA KEV details

CISA lists a CVE here once it has evidence of exploitation against real targets.

CISAThat month →

Listed

Sep 18, 2026

Federal deadline

Sep 21, 2026

passed 17 days ago

Ransomware use

Unknown

CISA records ransomware use only for campaigns it has confirmed, so “Unknown” means unrecorded, not ruled out. The deadline binds US federal agencies; for everyone else it is a date to argue against.

Public exploit

Capability, not use: code existing is a different claim from anyone running it.

Repositories

1 of the 5 sampled are weaponized

Social mentions

Posts naming this CVE. Attention, not evidence of exploitation — it spikes on disclosure and decays whether or not anything is exploited.

Critical #SUSE kernel patches released for CVE-2023-53676 (8.5), CVE-2025-39682 (7.0), and CVE-2025-40204 (8.7). Read more: 👉 https://t.co/0JRU7UQyiA #Security https://t.co/4FhU1EHYHH
@Cezar_H_Linux· Jan 22, 2026

Detection

Read off the CVSS vector and the weakness class. Starting points, not rules we have tested.

Prioritize edge telemetry for network-reachable Linux, azl3 kernel 6.6.96.2-1 on Azure Linux 3.0, azl3 kernel 6.6.96.2-2 on Azure Linux 3.0.
Monitor for scanner or exploit-pattern traffic after 7 public PoC repositories were reported.

web/proxy/WAF logsapplication logsnetwork IDS/IPS

Timeline

What happened to this CVE, newest first — with the readings a source repeats on a schedule counted underneath rather than listed.

2026
Added · CVSS 3.1 9.8 (AV:N)
Sep 21, 2026 · NVD
Added to CISA KEV catalog
Sep 18, 2026 · CISA
2025
Bulletin released on NIST.
Sep 9, 2025 · SOCRadar CTI
Bulletin released on NIST.
Sep 6, 2025 · SOCRadar CTI
Initial · CVE published
Sep 5, 2025 · NVD
Added · GHSA-v2pf-75pf-9c5h published (high)
Sep 5, 2025 · GitHub Security Advisory
CVE published by MITRE.
Sep 5, 2025 · SOCRadar CTI

Source activity

Readings a source repeats on a schedule, counted rather than listed.

3×ModifiedJan 27, 2026 – Jul 30, 2026 · SOCRadar CTI
2×Tweets · 1 time tweeted.Sep 7, 2025 – Jan 23, 2026 · SOCRadar CTI
1×SVRS is calculatedOct 16, 2025 · SOCRadar CTI
1×Github_Repos · Github repository created, khoatran107/cve-2025-39682Oct 14, 2025 · SOCRadar CTI

References

22 on the record

git.kernel.org/stable/c/2902c3ebcca52ca845c03182000e8d71d3a5196f
Patch, NIST, Vendor Advisory
git.kernel.org/stable/c/29c0ce3c8cdb6dc5d61139c937f34cb888a6f42e
Patch, NIST, Vendor Advisory
git.kernel.org/stable/c/3439c15ae91a517cf3c650ea15a8987699416ad9
Patch, NIST, Vendor Advisory
git.kernel.org/stable/c/62708b9452f8eb77513115b17c4f8d1a22ebf843
Patch, NIST, Vendor Advisory
git.kernel.org/stable/c/c09dd3773b5950e9cfb6c9b9a5f6e36d06c62677
Patch, NIST, Vendor Advisory
lists.debian.org/debian-lts-announce/2025/10/msg00008.html
Mailing List, Third Party Advisory, NIST
cert-portal.siemens.com/productcert/html/ssa-032379.html
Third Party Advisory, NIST
www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2025-39682
US Government Resource

Coverage

19 stories from the feeds we poll

14 more reports on this CVEShowing 5 of 19 · Vendor research and security press coverageUnlock free

Elsewhere on this site

Linuxevery CVE for this vendor
Microsoftevery CVE for this vendor
September 2026what else CISA listed
Unclassifiedsame class
CWE-754other pages naming this weakness

Not in any source we poll

Listed rather than left blank: an empty field and an unmeasured one look identical on screen, and only one is a reason to look elsewhere.

No confirmed IOCs, IP addresses, domains, file hashes, or malware artifacts supplied.
No organization-specific asset inventory, compensating-control status, or patch deployment evidence supplied.
No exploit packet captures, log samples, or incident case IDs supplied.

Answered from this record1

What should defenders know first?

CVE-2025-39682 is tls: fix handling of zero-length records on the rx_list, a critical vulnerability affecting Linux, azl3 kernel 6.6.96.2-1 on Azure Linux 3.0, azl3 kernel 6.6.96.2-2 on Azure Linux 3.0 from Linux, Microsoft. The current evidence lists it in CISA KEV, and the exploit status is: Yes: CISA KEV signal present. Public exploit evidence is: 7 public PoC repositories reported; 1 marked weaponized in current dataset. The affected-version evidence is listed in the key facts and affected products tables. Defenders should first verify whether exposed or business-critical assets run those versions, then apply vendor patches or mitigations, restrict reachable attack surface, and preserve logs for detection review. CVSS 9.8 describes technical severity, while EPSS 3% helps estimate near-term exploit likelihood; neither replaces asset context. Unknown fields should remain explicit in tickets, and threat actor, IOC, victimology, or payload claims should not be added unless a cited source supports them. Monitor CISA KEV, vendor advisories, NVD changes, public PoC repositories, and internal telemetry for update triggers.