--- id: CVE-2025-39682 title: |- 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 re… 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 re… severity: critical cvss: 9.8 cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H' cwe: - CWE-754 vendor: linux product: linux_kernel affected: - 'linux_kernel >= 6.0, < 6.1.149' - 'linux_kernel >= 6.2, < 6.6.103' - 'linux_kernel >= 6.7, < 6.12.44' - 'linux_kernel >= 6.13, < 6.16.4' - linux_kernel = 6.17 - debian_linux = 11.0 - simatic_cn_4100_firmware < 5.0 patched: - linux_kernel 6.16.4 - simatic_cn_4100_firmware 5.0 published: '2025-09-05' updated: '2026-09-21' sourceUpdated: '2026-09-21T12:00:36.613' source: NVD sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2025-39682' references: - url: 'https://git.kernel.org/stable/c/2902c3ebcca52ca845c03182000e8d71d3a5196f' label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67 - url: 'https://git.kernel.org/stable/c/29c0ce3c8cdb6dc5d61139c937f34cb888a6f42e' label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67 - url: 'https://git.kernel.org/stable/c/3439c15ae91a517cf3c650ea15a8987699416ad9' label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67 - url: 'https://git.kernel.org/stable/c/62708b9452f8eb77513115b17c4f8d1a22ebf843' label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67 - url: 'https://git.kernel.org/stable/c/c09dd3773b5950e9cfb6c9b9a5f6e36d06c62677' label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67 - url: 'https://lists.debian.org/debian-lts-announce/2025/10/msg00008.html' label: af854a3a-2127-422b-91ae-364da2661108 - url: 'https://cert-portal.siemens.com/productcert/html/ssa-032379.html' label: 0b142b55-0307-4c5a-b3c9-f314f3fb7c5e - url: >- https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2025-39682 label: 134c704f-9b21-4f2e-91b3-4a467353bcc0 - url: >- https://security.access.redhat.com/data/csaf/v2/vex/2025/cve-2025-39682.json - url: 'https://access.redhat.com/security/cve/CVE-2025-39682' - url: 'https://bugzilla.redhat.com/show_bug.cgi?id=2393511' - url: 'https://www.cve.org/CVERecord?id=CVE-2025-39682' - url: 'https://nvd.nist.gov/vuln/detail/CVE-2025-39682' - url: >- https://lore.kernel.org/linux-cve-announce/2025090545-CVE-2025-39682-ddab@gregkh/T - url: 'https://www.cisa.gov/known-exploited-vulnerabilities-catalog' - url: 'https://access.redhat.com/errata/RHSA-2025:16904' - url: 'https://access.redhat.com/errata/RHSA-2025:19224' - url: 'https://access.redhat.com/errata/RHSA-2025:19104' - url: 'https://access.redhat.com/errata/RHSA-2025:16880' - url: 'https://access.redhat.com/errata/RHSA-2025:19223' tags: - nvd - kev - in-the-wild - exploit-available - cve.org - csaf - vex - red-hat - score-dispute epss: 0.0203 epssPercentile: 0.80202 kev: true kevDateAdded: '2026-09-18' kevDueDate: '2026-09-21' kevRansomware: false exploited: true exploits: github: 2 githubRepos: - 'https://github.com/khoatran107/cve-2025-39682' - 'https://github.com/suominen/CVE-2025-39682' checkedAt: '2026-09-24T07:52:53.338Z' exploitAvailable: true ssvc: exploitation: active automatable: 'yes' technicalImpact: total timestamp: '2026-09-18T19:25:58.427206Z' scores: nvd: 9.8 vendor: 7 ingestedAt: '2026-09-18T14:43:13.025Z' --- ## Overview 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. ## Affected - `linux_kernel >= 6.0, < 6.1.149` - `linux_kernel >= 6.2, < 6.6.103` - `linux_kernel >= 6.7, < 6.12.44` - `linux_kernel >= 6.13, < 6.16.4` - `linux_kernel = 6.17` - `debian_linux = 11.0` - `simatic_cn_4100_firmware < 5.0` ## Remediation Upgrade past the affected range: - `linux_kernel 6.16.4` - `simatic_cn_4100_firmware 5.0` ## Vendor advisories - **RHSA-2025:16904** · Red Hat · fixed in: Red Hat Enterprise Linux AppStream (v. 10), Red Hat Enterprise Linux BaseOS (v. 10), Red Hat Enterprise Linux CodeReady Linux Builder (v. 10), Red Hat Enterprise Linux Real Time for NFV (v. 10), Red Hat Enterprise Linux Real Time (v. 10) · released 2025-09-29 · [advisory](https://access.redhat.com/errata/RHSA-2025:16904) - **RHSA-2025:19224** · Red Hat · fixed in: Red Hat Enterprise Linux AppStream E4S (v.9.2), Red Hat Enterprise Linux BaseOS E4S (v.9.2) · released 2025-10-29 · [advisory](https://access.redhat.com/errata/RHSA-2025:19224) - **RHSA-2025:19104** · Red Hat · fixed in: Red Hat Enterprise Linux AppStream EUS (v.9.4), Red Hat Enterprise Linux BaseOS EUS (v.9.4), Red Hat CodeReady Linux Builder EUS (v.9.4), Red Hat Enterprise Linux Real Time for NFV EUS (v.9.4), Red Hat Enterprise Linux Real Time EUS (v.9.4) · released 2025-10-27 · [advisory](https://access.redhat.com/errata/RHSA-2025:19104) - **RHSA-2025:16880** · Red Hat · fixed in: Red Hat Enterprise Linux AppStream (v. 9), Red Hat Enterprise Linux BaseOS (v. 9), Red Hat Enterprise Linux CodeReady Linux Builder (v. 9), Red Hat Enterprise Linux Real Time for NFV (v. 9), Red Hat Enterprise Linux Real Time (v. 9) · released 2025-09-29 · [advisory](https://access.redhat.com/errata/RHSA-2025:16880) - **RHSA-2025:19223** · Red Hat · fixed in: Red Hat Enterprise Linux Real Time for NFV E4S (v.9.2), Red Hat Enterprise Linux Real Time E4S (v.9.2) · released 2025-10-29 · [advisory](https://access.redhat.com/errata/RHSA-2025:19223)