CVE-2025-39682 (GCVE-0-2025-39682)
Vulnerability from cvelistv5 – Published: 2025-09-05 17:20 – Updated: 2026-09-19 03:56Title
tls: fix handling of zero-length records on the rx_list
Summary
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.
Severity
9.8 (Critical)
SSVC
Exploitation: active
Automatable: yes
Technical Impact: total
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-09-18 00:00 UTC
CWE
- CWE-754 - Improper Check for Unusual or Exceptional Conditions
Assigner
References
8 references
Impacted products
3 products
| Vendor | Product | Version | CPE status | |
|---|---|---|---|---|
| Linux | Linux |
Affected:
84c61fe1a75b4255df1e1e7c054c9e6d048da417 , < 2902c3ebcca52ca845c03182000e8d71d3a5196f
(git)
Affected: 84c61fe1a75b4255df1e1e7c054c9e6d048da417 , < c09dd3773b5950e9cfb6c9b9a5f6e36d06c62677 (git) Affected: 84c61fe1a75b4255df1e1e7c054c9e6d048da417 , < 3439c15ae91a517cf3c650ea15a8987699416ad9 (git) Affected: 84c61fe1a75b4255df1e1e7c054c9e6d048da417 , < 29c0ce3c8cdb6dc5d61139c937f34cb888a6f42e (git) Affected: 84c61fe1a75b4255df1e1e7c054c9e6d048da417 , < 62708b9452f8eb77513115b17c4f8d1a22ebf843 (git) |
guessed | |
| Linux | Linux |
Affected:
6.0
Unaffected: 0 , < 6.0 (semver) Unaffected: 6.1.149 , ≤ 6.1.* (semver) Unaffected: 6.6.103 , ≤ 6.6.* (semver) Unaffected: 6.12.44 , ≤ 6.12.* (semver) Unaffected: 6.16.4 , ≤ 6.16.* (semver) Unaffected: 6.17 , ≤ * (original_commit_for_fix) |
guessed | |
| Siemens | SIMATIC CN 4100 |
Affected:
0 , < V5.0
(custom)
|
guessed |
CISA
Known Exploited Vulnerability - GCVE BCP-07 Compliant
KEV entry ID: 61617b0a-4c8f-4424-9587-02d63af5a527
Exploited: Yes
Timestamps
First Seen: 2026-09-18
Asserted: 2026-09-18
Scope
Notes: Linux Kernel Improper Check for Unusual or Exceptional Conditions Vulnerability | Affected: Linux / Kernel | Description: Linux Kernel contains an improper check for unusual or exceptional conditions vulnerability in the TLS receive path which allows a zero-length record retrieved from the rx_list to bypass the intended recvmsg() record-type handling, potentially causing subsequent TLS records to be processed using incorrect zero-copy and queuing assumptions. The impacted product(s) could be end-of-life (EoL) and/or end-of-service (EoS). Users are advised to discontinue use and/or transition to a supported version. | 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. | Due date: 2026-09-21 | Known ransomware campaign use (KEV): Unknown | Notes (KEV): This vulnerability affects an open-source component, third-party library, protocol, or proprietary implementation that could be used by different products. For more information, please see: ; https://git.kernel.org/stable/c/2902c3ebcca52ca845c03182000e8d71d3a5196f; https://git.kernel.org/stable/c/c09dd3773b5950e9cfb6c9b9a5f6e36d06c62677; https://git.kernel.org/stable/c/3439c15ae91a517cf3c650ea15a8987699416ad9; https://git.kernel.org/stable/c/29c0ce3c8cdb6dc5d61139c937f34cb888a6f42e; https://git.kernel.org/stable/c/62708b9452f8eb77513115b17c4f8d1a22ebf843 ; BOD 26-04: https://www.cisa.gov/news-events/directives/bod-26-04-prioritizing-security-updates-based-risk ; Forensics Triage Requirements: https://www.cisa.gov/news-events/directives/bod-26-04-implementation-guidance-prioritizing-security-updates-based-risk ; https://nvd.nist.gov/vuln/detail/CVE-2025-39682
Evidence
Type: Vendor Report
Signal: Successful Exploitation
Confidence: 80%
Source: cisa-kev
Details
| Cwes | CWE-754 |
|---|---|
| Feed | CISA Known Exploited Vulnerabilities Catalog |
| Product | Kernel |
| Due Date | 2026-09-21 |
| Date Added | 2026-09-18 |
| Vendorproject | Linux |
| Vulnerabilityname | Linux Kernel Improper Check for Unusual or Exceptional Conditions Vulnerability |
| Knownransomwarecampaignuse | Unknown |
References
Created: 2026-09-18 20:00 UTC
| Updated: 2026-09-18 20:00 UTC
Previdian
Known Exploited Vulnerability - GCVE BCP-07 Compliant
KEV entry ID: 21f76e95-2fa4-464b-b0be-ef2fc48d5693
Exploited: Yes
Timestamps
First Seen: 2026-09-18
Asserted: 2026-09-18
Scope
Notes: tls: fix handling of zero-length records on the rx_list | Affected: Linux / Linux | CVSS: 9.8 (CRITICAL) | EPSS: 0.00505 | Used in malware: unknown | Not yet in CISA KEV: False
Evidence
Type: Public Report
Signal: Successful Exploitation
Confidence: 70%
Source: previdian
Details
| Feed | Previdian (previdian.com) |
|---|---|
| Title | tls: fix handling of zero-length records on the rx_list |
| Cve Id | CVE-2025-39682 |
| Vendor | Linux |
| Ghsa Id | GHSA-V2PF-75PF-9C5H |
| Product | Linux |
| Added Date | 2026-09-18T19:20:38.811Z |
| Cvss Score | 9.8 |
| Epss Score | 0.00505 |
| Previous Ids | |
| Cvss Severity | CRITICAL |
| Virtual Patch | False |
| Cvss Estimated | False |
| Epss Percentile | 0.42129 |
| Used In Malware | unknown |
| Vulnerability Id | CVE-2025-39682 |
| Ahead Of Cisa Kev | None |
| Not Yet In Cisa Kev | False |
References
Created: 2026-09-19 20:00 UTC
| Updated: 2026-09-19 20:00 UTC
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Experimental. This forecast is provided for visualization only and may change without notice. Do not use it for operational decisions.
Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.
Sightings
| Author | Source | Type | Date | Other |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or observed by the user.
- Confirmed: The vulnerability has been validated from an analyst's perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
- Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
- Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
- Not confirmed: The user expressed doubt about the validity of the vulnerability.
- Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.
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The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the
vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base
model, served locally by ML-Gateway.
They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.
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Related by attack behaviour
Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.
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