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NVD / CVE Program· CNA Linux

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

Noroxi assessment

Priority: This week (action score 70/100)

  • CISA has confirmed exploitation in the wild (Sep 18, 2026). Remediation deadline for US federal agencies: Sep 21, 2026.
  • Probability of exploitation in the next 30 days: 3.2% (FIRST EPSS); higher than 88.2% of all records.
  • Anyone who can reach it over the internet can trigger it. No account or password is required. No user action is required. No special conditions are required; it is repeatable.
  • According to CISA the attack is automatable: targets can be found by mass scanning.
  • Fixed version: Linux Linux 2902c3ebcca52ca845c03182000e8d71d3a5196f, 29c0ce3c8cdb6dc5d61139c937f34cb888a6f42e, 3439c15ae91a517cf3c650ea15a8987699416ad9; azl3 kernel 6.6.96.2-2 on Azure Linux 3.0 6.6.104.2-1.

Don’t wait for the next maintenance window. Upgrade to Linux Linux 2902c3ebcca52ca845c03182000e8d71d3a5196f, 29c0ce3c8cdb6dc5d61139c937f34cb888a6f42e, 3439c15ae91a517cf3c650ea15a8987699416ad9; azl3 kernel 6.6.96.2-2 on Azure Linux 3.0 6.6.104.2-1 or later.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · CISA KEV · FIRST EPSS

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.

CriticalCVSS 9.8 · v3.1KEVWeaponized Fix available
Published
Sep 5, 2025
Updated
Oct 19, 2026
EPSS
3.2% · 88th percentile

Report tools

JSON

Action score

70

This week

Don’t wait for the next maintenance window.

CVSS
39 / 40 · 9.8 / 10
CISA KEV
30 / 30 · Listed
EPSS
1 / 30 · 3.2%

CISA SSVC decision

Exploitation
active
Automatable
yes
Technical impact
total

Vulnrichment: CISA's decision-tree inputs.

CNA vs NVD score

NVD
9.8
CNA · Linux
9.8
agree

The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.

Actively exploited in the wild

CISA added this to its Known Exploited Vulnerabilities catalog on Sep 18, 2026. That signals real attacks, not theory.

Remediation deadline for US federal agencies: Sep 21, 2026.

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  • In CISA KEV: exploitation in the wild confirmed
  • Weaponized exploit exists
  • A fix has been released

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Noroxi analysis

What does it mean in your environment?

The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.

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Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

VendorProduct
linuxlinux kernel
debiandebian linux
siemenssimatic cn 4100 firmware
siemenssimatic cn 4100

Affected versions

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

  • debian debian linux11.0
  • linux linux kernel6.2 and later · before 6.6.103
  • linux linux kernel6.7 and later · before 6.12.44
  • linux linux kernel6.0 and later · before 6.1.149
  • linux linux kernel6.13 and later · before 6.16.4
  • linux linux kernel6.17
  • siemens simatic cn 4100 firmwarebefore 5.0

Versions reported by the vendor

Affected version ranges reported by the assigning authority (Linux). Independent of NVD's CPE analysis and usually ahead of it.

  • Linux Linux

    • 6.0affected
    • 84c61fe1a75b4255df1e1e7c054c9e6d048da417 and later · before 2902c3ebcca52ca845c03182000e8d71d3a5196faffected · git
    • 84c61fe1a75b4255df1e1e7c054c9e6d048da417 and later · before c09dd3773b5950e9cfb6c9b9a5f6e36d06c62677affected · git
    • 84c61fe1a75b4255df1e1e7c054c9e6d048da417 and later · before 3439c15ae91a517cf3c650ea15a8987699416ad9affected · git
    • 84c61fe1a75b4255df1e1e7c054c9e6d048da417 and later · before 29c0ce3c8cdb6dc5d61139c937f34cb888a6f42eaffected · git
    • 84c61fe1a75b4255df1e1e7c054c9e6d048da417 and later · before 62708b9452f8eb77513115b17c4f8d1a22ebf843affected · git
    • before 6.0not affected · semver
    • 6.1.149 and later · up to and including 6.1.*not affected · semver
    • 6.6.103 and later · up to and including 6.6.*not affected · semver
    • 6.12.44 and later · up to and including 6.12.*not affected · semver

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

EcosystemPackageAffected rangeFix
AlmaLinux:10kernel-abi-stablelistsbefore 6.12.0-55.37.1.el10_06.12.0-55.37.1.el10_0
AlmaLinux:10kernel-docbefore 6.12.0-55.37.1.el10_06.12.0-55.37.1.el10_0
AlmaLinux:9kernelbefore 5.14.0-570.49.1.el9_65.14.0-570.49.1.el9_6
AlmaLinux:9kernel-64kbefore 5.14.0-570.49.1.el9_65.14.0-570.49.1.el9_6
AlmaLinux:9kernel-64k-corebefore 5.14.0-570.49.1.el9_65.14.0-570.49.1.el9_6
AlmaLinux:9kernel-64k-debugbefore 5.14.0-570.49.1.el9_65.14.0-570.49.1.el9_6
AlmaLinux:9kernel-64k-debug-corebefore 5.14.0-570.49.1.el9_65.14.0-570.49.1.el9_6
AlmaLinux:9kernel-64k-debug-develbefore 5.14.0-570.49.1.el9_65.14.0-570.49.1.el9_6
AlmaLinux:9kernel-64k-debug-devel-matchedbefore 5.14.0-570.49.1.el9_65.14.0-570.49.1.el9_6
AlmaLinux:9kernel-64k-debug-modulesbefore 5.14.0-570.49.1.el9_65.14.0-570.49.1.el9_6
AlmaLinux:9kernel-64k-debug-modules-corebefore 5.14.0-570.49.1.el9_65.14.0-570.49.1.el9_6
AlmaLinux:9kernel-64k-debug-modules-extrabefore 5.14.0-570.49.1.el9_65.14.0-570.49.1.el9_6
AlmaLinux:9kernel-64k-develbefore 5.14.0-570.49.1.el9_65.14.0-570.49.1.el9_6
AlmaLinux:9kernel-64k-devel-matchedbefore 5.14.0-570.49.1.el9_65.14.0-570.49.1.el9_6
AlmaLinux:9kernel-64k-modulesbefore 5.14.0-570.49.1.el9_65.14.0-570.49.1.el9_6
AlmaLinux:9kernel-64k-modules-corebefore 5.14.0-570.49.1.el9_65.14.0-570.49.1.el9_6
AlmaLinux:9kernel-64k-modules-extrabefore 5.14.0-570.49.1.el9_65.14.0-570.49.1.el9_6
AlmaLinux:9kernel-abi-stablelistsbefore 5.14.0-570.49.1.el9_65.14.0-570.49.1.el9_6
AlmaLinux:9kernel-corebefore 5.14.0-570.49.1.el9_65.14.0-570.49.1.el9_6
AlmaLinux:9kernel-cross-headersbefore 5.14.0-570.49.1.el9_65.14.0-570.49.1.el9_6
AlmaLinux:9kernel-debugbefore 5.14.0-570.49.1.el9_65.14.0-570.49.1.el9_6
AlmaLinux:9kernel-debug-corebefore 5.14.0-570.49.1.el9_65.14.0-570.49.1.el9_6
AlmaLinux:9kernel-debug-develbefore 5.14.0-570.49.1.el9_65.14.0-570.49.1.el9_6
AlmaLinux:9kernel-debug-devel-matchedbefore 5.14.0-570.49.1.el9_65.14.0-570.49.1.el9_6

+96

Same product

linux: all records

Other highest-scoring records for the same primary product.

  • CVE-2026-31431crypto: algif_aead - Revert to operating out-of-placeKEV
    90Now
  • CVE-2022-0847A flaw was found in the way the "flags" member of the new pipe buffer structure was lacking proper initialization in copy_page_to_iter_pipe KEV
    89Now
  • CVE-2021-22555Heap Out-Of-Bounds Write in Netfilter IP6T_SO_SET_REPLACEKEV
    85Now

Published before and after this one in the same product

  • ← EarlierCVE-2025-39680Sep 5, 2025 · i2c: rtl9300: Fix out-of-bounds bug in rtl9300_i2c_smbus_xfer
    28Monitor
  • ← EarlierCVE-2025-39681Sep 5, 2025 · x86/cpu/hygon: Add missing resctrl_cpu_detect() in bsp_init helper
    22Monitor
  • Later →CVE-2025-39683Sep 5, 2025 · tracing: Limit access to parser->buffer when trace_get_user failed
    28Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / packageFixed versionSource
Linux Linux2902c3ebcca52ca845c03182000e8d71d3a5196fVendor (CNA)
Linux Linux29c0ce3c8cdb6dc5d61139c937f34cb888a6f42eVendor (CNA)
Linux Linux3439c15ae91a517cf3c650ea15a8987699416ad9Vendor (CNA)
Linux Linux62708b9452f8eb77513115b17c4f8d1a22ebf843Vendor (CNA)
Linux Linuxc09dd3773b5950e9cfb6c9b9a5f6e36d06c62677Vendor (CNA)
azl3 kernel 6.6.96.2-2 on Azure Linux 3.06.6.104.2-1 · CBL-Mariner ReleasesMicrosoft (MSRC)
almalinux:kernel5.14.0-570.49.1.el9_6 · AlmaLinux:9Package registry (OSV)
almalinux:kernel-64k5.14.0-570.49.1.el9_6 · AlmaLinux:9Package registry (OSV)
almalinux:kernel-64k-core5.14.0-570.49.1.el9_6 · AlmaLinux:9Package registry (OSV)
almalinux:kernel-64k-debug5.14.0-570.49.1.el9_6 · AlmaLinux:9Package registry (OSV)
almalinux:kernel-64k-debug-core5.14.0-570.49.1.el9_6 · AlmaLinux:9Package registry (OSV)
almalinux:kernel-64k-debug-devel5.14.0-570.49.1.el9_6 · AlmaLinux:9Package registry (OSV)
almalinux:kernel-64k-debug-devel-matched5.14.0-570.49.1.el9_6 · AlmaLinux:9Package registry (OSV)
almalinux:kernel-64k-debug-modules5.14.0-570.49.1.el9_6 · AlmaLinux:9Package registry (OSV)
almalinux:kernel-64k-debug-modules-core5.14.0-570.49.1.el9_6 · AlmaLinux:9Package registry (OSV)
almalinux:kernel-64k-debug-modules-extra5.14.0-570.49.1.el9_6 · AlmaLinux:9Package registry (OSV)
almalinux:kernel-64k-devel5.14.0-570.49.1.el9_6 · AlmaLinux:9Package registry (OSV)
almalinux:kernel-64k-devel-matched5.14.0-570.49.1.el9_6 · AlmaLinux:9Package registry (OSV)
debian:linux6.1.153-1 · Debian:12Package registry (OSV)
red hat:kernel-64k-debug-debuginfo0:5.14.0-570.49.1.el9_6 · Red Hat:enterprise_linux:9::appstreamPackage registry (OSV)
red hat:kernel-64k-debug-devel0:5.14.0-570.49.1.el9_6 · Red Hat:enterprise_linux:9::appstreamPackage registry (OSV)
red hat:kernel-64k-debug-devel-matched0:5.14.0-570.49.1.el9_6 · Red Hat:enterprise_linux:9::appstreamPackage registry (OSV)
red hat:kernel-64k-debuginfo0:5.14.0-570.49.1.el9_6 · Red Hat:enterprise_linux:9::appstreamPackage registry (OSV)
red hat:kernel-64k-devel0:5.14.0-570.49.1.el9_6 · Red Hat:enterprise_linux:9::appstreamPackage registry (OSV)
red hat:kernel-64k-devel-matched0:5.14.0-570.49.1.el9_6 · Red Hat:enterprise_linux:9::appstreamPackage registry (OSV)
red hat:kernel-debug-debuginfo0:5.14.0-570.49.1.el9_6 · Red Hat:enterprise_linux:9::appstreamPackage registry (OSV)
red hat:kernel-debug-devel0:5.14.0-570.49.1.el9_6 · Red Hat:enterprise_linux:9::appstreamPackage registry (OSV)
red hat:kernel-debug-devel-matched0:5.14.0-570.49.1.el9_6 · Red Hat:enterprise_linux:9::appstreamPackage registry (OSV)
red hat:kernel-debuginfo0:5.14.0-570.49.1.el9_6 · Red Hat:enterprise_linux:9::appstreamPackage registry (OSV)
red hat:kernel-debuginfo-common-aarch640:5.14.0-570.49.1.el9_6 · Red Hat:enterprise_linux:9::appstreamPackage registry (OSV)

+14

Exploit status

Weaponized

A ready exploit tool or active in-the-wild use is known for this vulnerability. This should be your top priority.

Evidence

  • Proof-of-concept repository on GitHub ×2

Noroxi does not host or link to exploit code. Metasploit module names and Nuclei template ids are shown (names, not code); Exploit-DB entries and PoC repositories are given as counts only.

Public exploit evidence
SourceKindDate
Proof-of-concept repository on GitHubstars:62025-10-14
Proof-of-concept repository on GitHubstars:02026-09-20

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

  1. Published
  2. First PoC+38 d
  3. CISA KEV+377 d
  4. TodayOct 28, 2026+418 d
EPSS, last 120 days

FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

No commit or PR link among the references.

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

No credits in the CNA record.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

  • CVE-2026-31637231 days apartrxrpc: reject undecryptable rxkad response tickets
    39Monitor
  • CVE-2026-31666231 days apartbtrfs: fix incorrect return value after changing leaf in lookup_extent_data_ref()
    31Monitor
  • CVE-2026-43133243 days apartKVM: nSVM: Always use vmcb01 in VMLOAD/VMSAVE emulation
    31Monitor
  • CVE-2026-63841317 days apartdrm/amdgpu/jpeg: set no_user_fence for JPEG v5.0.1 ring
    31Monitor
  • CVE-2026-63843317 days apartdrm/amdgpu/jpeg: set no_user_fence for JPEG v4.0.5 ring
    31Monitor
  • CVE-2026-63847317 days apartdrm/amdgpu/jpeg: set no_user_fence for JPEG v2.5 ring
    31Monitor

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

—

Bug bounty scope

No known public program.

Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).

Noroxi's write-up

Our blog post on this record: impact, how to check your site and the upgrade steps.

CVE-2025-39682: Linux kernel kTLS memory flaw. Is your server affected?

Technical details

Attack conditions

  • Anyone who can reach it over the internet can trigger it.
  • No account or password is required.
  • No user action is required.
  • No special conditions are required; it is repeatable.

If successful

Confidentiality
high · data can be read
Integrity
high · data or configuration can be modified
Availability
high · the service can be disrupted
Attack vector
Network
Attack complexity
Low
Privileges required
None
User interaction
None
Scope
Unchanged
Confidentiality impact
High
Integrity impact
High
Availability impact
High

Weakness class (CWE)

CWE-754 · Improper Check for Unusual or Exceptional Conditions

CVSS vector

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

nvd-primary

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

MITRE has no CAPEC/ATT&CK mapping for this CWE.

Change log

  1. Fix✗ → ✓

For records you follow, these changes also arrive as notifications. →

References

Show all references (7 more)

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records