Vulnerability-Lookup

FKIE_CVE-2025-39682

Vulnerability from fkie_nvd - Published: 2025-09-05 18:15 - Updated: 2026-10-19 21:10

Severity

9.8 (Critical) - CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
9.8 (Critical) - CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

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.

References

URL	Tags
416baaa9-dc9f-4396-8d5f-8c081fb06d67	https://git.kernel.org/stable/c/2902c3ebcca52ca845c03182000e8d71d3a5196f	Patch
416baaa9-dc9f-4396-8d5f-8c081fb06d67	https://git.kernel.org/stable/c/29c0ce3c8cdb6dc5d61139c937f34cb888a6f42e	Patch
416baaa9-dc9f-4396-8d5f-8c081fb06d67	https://git.kernel.org/stable/c/3439c15ae91a517cf3c650ea15a8987699416ad9	Patch
416baaa9-dc9f-4396-8d5f-8c081fb06d67	https://git.kernel.org/stable/c/62708b9452f8eb77513115b17c4f8d1a22ebf843	Patch
416baaa9-dc9f-4396-8d5f-8c081fb06d67	https://git.kernel.org/stable/c/c09dd3773b5950e9cfb6c9b9a5f6e36d06c62677	Patch
af854a3a-2127-422b-91ae-364da2661108	https://lists.debian.org/debian-lts-announce/2025/10/msg00008.html	Mailing List, Third Party Advisory
0b142b55-0307-4c5a-b3c9-f314f3fb7c5e	https://cert-portal.siemens.com/productcert/html/ssa-032379.html	Third Party Advisory
134c704f-9b21-4f2e-91b3-4a467353bcc0	https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2025-39682	US Government Resource

Impacted products

Vendor	Product	Version
linux	linux_kernel	*
linux	linux_kernel	*
linux	linux_kernel	*
linux	linux_kernel	*
linux	linux_kernel	6.17
linux	linux_kernel	6.17
debian	debian_linux	11.0
siemens	simatic_cn_4100_firmware	*
siemens	simatic_cn_4100	-

JSON

To clipboard

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      "affectedData": [
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          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
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              "version": "6.12.44",
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              "version": "6.16.4",
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  "cisaActionDue": "2026-09-21",
  "cisaExploitAdd": "2026-09-18",
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  ],
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "In the Linux kernel, the following vulnerability has been resolved:\n\ntls: fix handling of zero-length records on the rx_list\n\nEach recvmsg() call must process either\n - only contiguous DATA records (any number of them)\n - one non-DATA record\n\nIf the next record has different type than what has already been\nprocessed we break out of the main processing loop. If the record\nhas already been decrypted (which may be the case for TLS 1.3 where\nwe don\u0027t know type until decryption) we queue the pending record\nto the rx_list. Next recvmsg() will pick it up from there.\n\nQueuing the skb to rx_list after zero-copy decrypt is not possible,\nsince in that case we decrypted directly to the user space buffer,\nand we don\u0027t have an skb to queue (darg.skb points to the ciphertext\nskb for access to metadata like length).\n\nOnly data records are allowed zero-copy, and we break the processing\nloop after each non-data record. So we should never zero-copy and\nthen find out that the record type has changed. The corner case\nwe missed is when the initial record comes from rx_list, and it\u0027s\nzero length."
    },
    {
      "lang": "es",
      "value": "En el kernel de Linux, la siguiente vulnerabilidad ha sido resuelta:\n\ntls: soluciona el manejo de registros de longitud cero en la rx_list\n\nCada llamada a recvmsg() debe procesar o bien\n- solo registros DATA contiguos (cualquier n\u00famero de ellos)\n- un registro que no sea DATA\n\nSi el siguiente registro tiene un tipo diferente al que ya ha sido procesado, salimos del bucle de procesamiento principal. Si el registro ya ha sido descifrado (lo cual puede ocurrir con TLS 1.3 donde no conocemos el tipo hasta el descifrado), ponemos en cola el registro pendiente en la rx_list. La siguiente recvmsg() lo recoger\u00e1 de ah\u00ed.\n\nPoner en cola el skb en la rx_list despu\u00e9s del descifrado de copia cero no es posible, ya que en ese caso desciframos directamente al b\u00fafer del espacio de usuario, y no tenemos un skb para poner en cola (darg.skb apunta al skb del texto cifrado para acceder a metadatos como la longitud).\n\nSolo a los registros de datos se les permite la copia cero, y rompemos el bucle de procesamiento despu\u00e9s de cada registro que no sea de datos. As\u00ed que nunca deber\u00edamos hacer copia cero y luego descubrir que el tipo de registro ha cambiado. El caso excepcional que pasamos por alto es cuando el registro inicial proviene de la rx_list, y es de longitud cero."
    }
  ],
  "id": "CVE-2025-39682",
  "lastModified": "2026-10-19T21:10:00.160",
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    "cvssMetricV31": [
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        "cvssData": {
          "attackComplexity": "LOW",
          "attackVector": "NETWORK",
          "availabilityImpact": "HIGH",
          "baseScore": 9.8,
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          "confidentialityImpact": "HIGH",
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          "privilegesRequired": "NONE",
          "scope": "UNCHANGED",
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CVE-2025-39682 (GCVE-0-2025-39682)

Vulnerability from cvelistv5 – Published: 2025-09-05 17:20 – Updated: 2026-10-07 17:56

Title

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

Summary

Severity

9.8 (Critical)


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

SSVC

Exploitation: active Automatable: yes Technical Impact: total

CISA Coordinator · CISA-ADP (v2.0.3)

Decision recorded 2026-09-19 03:56 UTC

CWE

CWE-754 - Improper Check for Unusual or Exceptional Conditions

Assigner

Linux CNA under the mitre root

CNA scorecard D 53/100 over 6643 records in the last 180 days details

References

8 references

URL	Tags
https://git.kernel.org/stable/c/2902c3ebcca52ca84…
https://git.kernel.org/stable/c/c09dd3773b5950e9c…
https://git.kernel.org/stable/c/3439c15ae91a517cf…
https://git.kernel.org/stable/c/29c0ce3c8cdb6dc5d…
https://git.kernel.org/stable/c/62708b9452f8eb775…
https://lists.debian.org/debian-lts-announce/2025…
https://cert-portal.siemens.com/productcert/html/…
https://www.cisa.gov/known-exploited-vulnerabilit…	government-resource

Impacted products

3 products

Vendor	Product	Version
Linux	Linux	Affected: 84c61fe1a75b4255df1e1e7c054c9e6d048da417 , < 2902c3ebcca52ca845c03182000e8d71d3a5196f (git) Affected: 84c61fe1a75b4255df1e1e7c054c9e6d048da417 , < c09dd3773b5950e9cfb6c9b9a5f6e36d06c62677 (git) Affected: 84c61fe1a75b4255df1e1e7c054c9e6d048da417 , < 3439c15ae91a517cf3c650ea15a8987699416ad9 (git) Affected: 84c61fe1a75b4255df1e1e7c054c9e6d048da417 , < 29c0ce3c8cdb6dc5d61139c937f34cb888a6f42e (git) Affected: 84c61fe1a75b4255df1e1e7c054c9e6d048da417 , < 62708b9452f8eb77513115b17c4f8d1a22ebf843 (git)
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)
Siemens	SIMATIC CN 4100	Affected: 0 , < V5.0 (custom)

Show details on NVD website

JSON

To clipboard

{
  "containers": {
    "adp": [
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        "providerMetadata": {
          "dateUpdated": "2025-11-03T17:42:13.673Z",
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        "references": [
          {
            "url": "https://lists.debian.org/debian-lts-announce/2025/10/msg00008.html"
          }
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        "title": "CVE Program Container"
      },
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            "defaultStatus": "unknown",
            "product": "SIMATIC CN 4100",
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            "versions": [
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            "tags": [
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            ],
            "url": "https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2025-39682"
          }
        ],
        "title": "CISA ADP Vulnrichment"
      }
    ],
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "net/tls/tls_sw.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "2902c3ebcca52ca845c03182000e8d71d3a5196f",
              "status": "affected",
              "version": "84c61fe1a75b4255df1e1e7c054c9e6d048da417",
              "versionType": "git"
            },
            {
              "lessThan": "c09dd3773b5950e9cfb6c9b9a5f6e36d06c62677",
              "status": "affected",
              "version": "84c61fe1a75b4255df1e1e7c054c9e6d048da417",
              "versionType": "git"
            },
            {
              "lessThan": "3439c15ae91a517cf3c650ea15a8987699416ad9",
              "status": "affected",
              "version": "84c61fe1a75b4255df1e1e7c054c9e6d048da417",
              "versionType": "git"
            },
            {
              "lessThan": "29c0ce3c8cdb6dc5d61139c937f34cb888a6f42e",
              "status": "affected",
              "version": "84c61fe1a75b4255df1e1e7c054c9e6d048da417",
              "versionType": "git"
            },
            {
              "lessThan": "62708b9452f8eb77513115b17c4f8d1a22ebf843",
              "status": "affected",
              "version": "84c61fe1a75b4255df1e1e7c054c9e6d048da417",
              "versionType": "git"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "net/tls/tls_sw.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "6.0"
            },
            {
              "lessThan": "6.0",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.1.*",
              "status": "unaffected",
              "version": "6.1.149",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.6.*",
              "status": "unaffected",
              "version": "6.6.103",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.12.*",
              "status": "unaffected",
              "version": "6.12.44",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.16.*",
              "status": "unaffected",
              "version": "6.16.4",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "6.17",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
            {
              "cpeMatch": [
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.1.149",
                  "versionStartIncluding": "6.0",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.6.103",
                  "versionStartIncluding": "6.0",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.12.44",
                  "versionStartIncluding": "6.0",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.16.4",
                  "versionStartIncluding": "6.0",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.17",
                  "versionStartIncluding": "6.0",
                  "vulnerable": true
                }
              ],
              "negate": false,
              "operator": "OR"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\ntls: fix handling of zero-length records on the rx_list\n\nEach recvmsg() call must process either\n - only contiguous DATA records (any number of them)\n - one non-DATA record\n\nIf the next record has different type than what has already been\nprocessed we break out of the main processing loop. If the record\nhas already been decrypted (which may be the case for TLS 1.3 where\nwe don\u0027t know type until decryption) we queue the pending record\nto the rx_list. Next recvmsg() will pick it up from there.\n\nQueuing the skb to rx_list after zero-copy decrypt is not possible,\nsince in that case we decrypted directly to the user space buffer,\nand we don\u0027t have an skb to queue (darg.skb points to the ciphertext\nskb for access to metadata like length).\n\nOnly data records are allowed zero-copy, and we break the processing\nloop after each non-data record. So we should never zero-copy and\nthen find out that the record type has changed. The corner case\nwe missed is when the initial record comes from rx_list, and it\u0027s\nzero length."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "baseScore": 9.8,
            "baseSeverity": "CRITICAL",
            "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
            "version": "3.1"
          },
          "scenarios": [
            {
              "lang": "en",
              "value": "AV:N - The bug is triggered entirely by the sequence and content of TLS records arriving from the remote peer on a kTLS-enabled TCP socket (net/tls RX path); no local access is needed. Any kTLS RX consumer \u2014 OpenSSL-with-kTLS servers/clients, NFS-over-TLS, SMB/RPC-over-TLS via net/handshake \u2014 is remotely reachable over the network.\nAC:L - The attacker sends three back-to-back records ([DATA][zero-length non-DATA][DATA]) and the corruption occurs deterministically on the victim\u0027s ordinary recvmsg() loop, with no race to win and no memory-layout dependency; the kernel selftest added with the fix reproduces it in one shot. TLS 1.2 is zero-copy-capable by default (zc_capable = rx_no_pad || version != TLS_1_3_VERSION), so no unusual kernel config or sockopt is required.\nPR:N - The attacker is the remote TLS peer, which holds no privileges on the target system \u2014 an anonymous client completing a server-authenticated TLS handshake with a kTLS server, or a malicious server that a kTLS client connects to, suffices. This matches the repo\u0027s PR:N scoring of the comparable remote-peer net/tls bug CVE-2025-39946.\nUI:N - The victim application only has to run its normal recvmsg() loop on an already-established kTLS socket; no click, mount, file open, or any other victim action is required. The attacker drives the entire trigger from the wire.\nS:U - The corruption is confined to kernel skb/slab state within the same security authority; there is no VM, IOMMU, or sandbox boundary crossed. Standard in-kernel memory corruption is Scope:Unchanged.\nC:H - The strparser anchor is queued on rx_list after tcp_read_done() already released its backing TCP skbs, so the next recvmsg() copies freed kernel heap memory straight into the userspace buffer via skb_copy_datagram_msg(). This is a directly usable, repeatable kernel-memory disclosure primitive, not a bounded pointer leak.\nI:H - The live strp-\u003eanchor is consume_skb()\u0027d by process_rx_list() while the strparser still uses it, after which incoming attacker-controlled TCP data is written into the freed sk_buff/skb_shared_info (skb_fill_page_desc, tls_strp_load_anchor_with_queue), and socket teardown double-frees the anchor and its frag_list skbs. This yields attacker-controlled write-after-free and freelist corruption suitable for control-flow hijack.\nA:H - The use-after-free and double-free of the anchor and of already-released TCP receive-queue skbs reliably corrupt slab state, producing oopses/panics and list corruption. Any remote peer can repeat this on every connection, giving a trivial remote kernel-crash DoS."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-08-05T12:04:31.384Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/2902c3ebcca52ca845c03182000e8d71d3a5196f"
        },
        {
          "url": "https://git.kernel.org/stable/c/c09dd3773b5950e9cfb6c9b9a5f6e36d06c62677"
        },
        {
          "url": "https://git.kernel.org/stable/c/3439c15ae91a517cf3c650ea15a8987699416ad9"
        },
        {
          "url": "https://git.kernel.org/stable/c/29c0ce3c8cdb6dc5d61139c937f34cb888a6f42e"
        },
        {
          "url": "https://git.kernel.org/stable/c/62708b9452f8eb77513115b17c4f8d1a22ebf843"
        }
      ],
      "title": "tls: fix handling of zero-length records on the rx_list",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2025-39682",
    "datePublished": "2025-09-05T17:20:48.657Z",
    "dateReserved": "2025-04-16T07:20:57.113Z",
    "dateUpdated": "2026-10-07T17:56:14.826Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}

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.

Vulnerability timeline

Sightings and recorded dates, grouped by day · UTC

Order JSON

How durations are calculated

Following the VTEM framework (Black Hat USA 2015), time to patch starts when the vendor or a coordinator was informed, total time to patch at discovery, and disclosure to patch at public disclosure; vendor response time runs from the report to its acknowledgement. Time to exploit and time unpatched start at the earliest discovery or report, falling back to public disclosure. Unpatched time ends at the first recorded patch, or the calculation time when no patch is recorded. Exploitation to patch shows the interval between those two events; a published proof of concept is a public exploit, not exploitation.

Each result shows its source dates. A negative interval means the end event came first; when date-only inputs leave the order open, the result says so. Date-only inputs are approximate. The earliest evidence wins: KEV report dates and sightings are labelled as such. Records describing another vulnerability are listed but never calculated from, and a PoC alone does not establish exploitation. Missing patch evidence does not prove that no patch exists. Filters below change the event list only.

Publication & reservation Sightings KEV catalogs Other timestamps

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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.

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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