Status: KEV | Advisory ID: CVE-2025-39682
| CVE | CVE-2025-39682 |
| Vulnerability Name | Linux Kernel Improper Check for Unusual or Exceptional Conditions Vulnerability |
| CVSS Score / Version | 9.8 (Critical) / CVSS v3.1 |
| Updated | 2026-09-20 |
| CVSS Vector | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H |
| CVSS Prose | attack vector is network; attack complexity is low; privileges required is none; user interaction is none; scope is unchanged; confidentiality impact is high; integrity impact is high; availability impact is high. |
| Affected products | Linux Kernel, Linux Linux Kernel, and debian Debian Linux |
| Exploitation status | Listed in CISA's Known Exploited Vulnerabilities (KEV) catalog, indicating confirmed active exploitation. |
| Classified as | CWE-754 (Improper Check for Unusual or Exceptional Conditions) |
| KEV listing | Added to CISA's Known Exploited Vulnerabilities (KEV) catalog on 2026-09-18. |
| Exploitation prediction (EPSS) | 2.88% probability of exploitation in the next 30 days (86% percentile) -- FIRST.org's EPSS model. |
| Federal remediation deadline | 2026-09-21 (CISA KEV, Binding Operational Directive). |
| Vendor | Product | Affected Versions | Patch Status |
|---|---|---|---|
| Linux | Kernel | ||
| Linux | Linux Kernel | ||
| debian | Debian Linux |
| Subsystems | Core Infrastructure |
| Sectors | All Sectors |
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.
Monitor Linux's and debian's web pages for any future patch releases.
| Source | Reference |
|---|---|
| NVD | https://nvd.nist.gov/vuln/detail/CVE-2025-39682 |
| CVE | https://www.cve.org/CVERecord?id=CVE-2025-39682 |
| Field | Value |
|---|---|
| KEV Link | https://www.cisa.gov/known-exploited-vulnerabilities-catalog |
| Date Added to KEV | 2026-09-18 |
| Required Action Due Date | 2026-09-21 |
| 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. |