CVE-2025-39682
Linux Kernel Improper Check for Unusual or Exceptional Conditions
- Published5 Sept 2025
- Added to CISA KEV18 Sept 2026
- Remediation due21 Sept 2026
Description
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.
CVSS 3.1 breakdown
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:HAffected products
Remediation
- https://git.kernel.org/stable/c/2902c3ebcca52ca845c03182000e8d71d3a5196f
- https://git.kernel.org/stable/c/29c0ce3c8cdb6dc5d61139c937f34cb888a6f42e
- https://git.kernel.org/stable/c/3439c15ae91a517cf3c650ea15a8987699416ad9
- https://git.kernel.org/stable/c/62708b9452f8eb77513115b17c4f8d1a22ebf843
- https://git.kernel.org/stable/c/c09dd3773b5950e9cfb6c9b9a5f6e36d06c62677
References
- https://cert-portal.siemens.com/productcert/html/ssa-032379.html
- https://git.kernel.org/stable/c/2902c3ebcca52ca845c03182000e8d71d3a5196f
- https://git.kernel.org/stable/c/29c0ce3c8cdb6dc5d61139c937f34cb888a6f42e
- https://git.kernel.org/stable/c/3439c15ae91a517cf3c650ea15a8987699416ad9
- https://git.kernel.org/stable/c/62708b9452f8eb77513115b17c4f8d1a22ebf843
- https://git.kernel.org/stable/c/c09dd3773b5950e9cfb6c9b9a5f6e36d06c62677
- https://lists.debian.org/debian-lts-announce/2025/10/msg00008.html
- https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2025-39682
Related CVEs
Recent high-severity vulnerabilities sharing a weakness type.
Frequently asked
Is CVE-2025-39682 being actively exploited?
Yes. CVE-2025-39682 is listed in the CISA Known Exploited Vulnerabilities (KEV) catalog, added 18 Sept 2026.
How severe is CVE-2025-39682?
CVE-2025-39682 has a CVSS 3.1 base score of 9.8, rated critical. EPSS estimates a 2.88% probability of exploitation.
Which products are affected by CVE-2025-39682?
Affected products include Debian Linux, Linux Kernel, Siemens Simatic Cn 4100 Firmware.
How do I fix CVE-2025-39682?
Upgrade affected software to a fixed version, for example Linux Kernel 6.1.149, Siemens Simatic Cn 4100 Firmware 5.0 or later, then confirm no affected versions remain in your inventory.
How Secuno handles this
Secuno correlates vulnerabilities like CVE-2025-39682 against the real software inventory on every managed device, as each hourly inventory arrives. Rather than a static severity, each match is scored in context: exploit availability, EPSS, the asset's exposure, and business criticality decide where it lands in the queue. Because it is on the CISA KEV list, a risk for it never ranks below high, and the update that fixes it moves to the Emergency patch lane. If an affected version is present anywhere across your portfolio, it surfaces automatically with a prioritised remediation path.
Data from the NVD, CISA KEV catalog and FIRST EPSS. CVSS 3.1 base score shown where available.