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CVE-2026-74735— l2tp: fix tunnel and session refcount leak on seq_file release

Quick assessment

Affected
Linux Linux
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

在 Linux 内核中，以下漏洞已得到修复： l2tp：修复 seq_file 释放时的隧道和会话引用计数泄漏 在 和 中，迭代状态（ 和 ）被保存在 seq_file 的私有数据中，以便支持跨多次 系统调用的持续迭代。 然而，如果用户空间在读取到文件末尾（EOF）之前关闭了 或 ，那么存储在 / 中的任何隧道或会话引用都会在 seq_file 私有数据被释放时未被释放（即引用计数未递减）。 修复方法： 在关闭文件时，通过 和 中释放（递减）剩余的 和 引用，从而解决该问题。

AI Predicted 3.1 Difficulty: Moderate EPSS 0.16% · P6

Affected Version Matrix 12

VendorProduct Version RangeStatus
Linux Linux 0e0c3fee3a59a387aeecc4fca6f3a2e9615a5443< ebe2774e956482dd3c70b8991f6f7654356339e6 affected
0e0c3fee3a59a387aeecc4fca6f3a2e9615a5443< 9006c116dd111d457bf5d074990210f70a4ad2c8 affected
f6104e9ae04462523c372928b1173766a771ef95 affected
7f8e401f9e612df2a95c1ef76217c00181389bb5 affected
c712ed63e9b33d9a282fbd92ce25c64918c3129f affected
9a8863e8a8def9d88583cd9c60db38a008e6b8cf affected
3.16.60< 3.17 affected
4.16.6< 4.17 affected
… +4 more rows
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I. Basic Information for CVE-2026-74735

Vulnerability Information
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Vulnerability Title
l2tp: fix tunnel and session refcount leak on seq_file release
Source: CVE Program / CVE List V5
Vulnerability Description
In the Linux kernel, the following vulnerability has been resolved: l2tp: fix tunnel and session refcount leak on seq_file release In pppol2tp_proc_open() and l2tp_dfs_seq_open(), iteration state (pd->tunnel and pd->session) is kept in seq_file private data to allow iteration across multiple read() system calls. However, if userspace closes /proc/net/pppol2tp or /sys/kernel/debug/l2tp/tunnels before reading to end-of-file (EOF), any tunnel or session reference stored in pd->tunnel / pd->session is left un-dropped when seq_file private data is freed. Fix this by dropping any remaining pd->tunnel and pd->session references in pppol2tp_proc_release() and l2tp_dfs_seq_release() when closing the file.
Source: CVE Program / CVE List V5
CVSS Information
N/A
Source: CVE Program / CVE List V5
Vulnerability Type
N/A
Source: CVE Program / CVE List V5

Affected Products

Vendor Product Affected Versions CPE Subscribe
Linux Linux 0e0c3fee3a59a387aeecc4fca6f3a2e9615a5443 ~ ebe2774e956482dd3c70b8991f6f7654356339e6 -
Linux Linux 4.17 -

II. Public POCs for CVE-2026-74735

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III. Intelligence Information for CVE-2026-74735

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Patches & Fixes for CVE-2026-74735 (2)

Same Patch Batch · Linux · 2026-08-26 · 92 CVEs total

CVE-2026-80561 9.8 CRITICAL libceph: fix multiple unsafe decodes in decode_locker()
CVE-2026-80587 9.8 CRITICAL mptcp: avoid combining some incoming suboptions
CVE-2026-74737 9.8 CRITICAL net: ethernet: ti: am65-cpsw-nuss: Fix port_id extraction from SRC TAG
CVE-2026-80589 9.8 CRITICAL block: stop the timeout timer when releasing a never added disk
CVE-2026-74743 9.8 CRITICAL macvlan: inherit needed_headroom and needed_tailroom from lowerdev
CVE-2026-80586 9.8 CRITICAL mptcp: options: reset DSS fields in case of unexpected size
CVE-2026-74744 9.8 CRITICAL ipvlan: inherit needed_headroom and needed_tailroom from phy_dev
CVE-2026-74746 9.8 CRITICAL netfilter: flowtable: publish GC-visible tuple last
CVE-2026-80519 9.8 CRITICAL ovpn: finish crypto callback cleanup before peer release
CVE-2026-80557 9.8 CRITICAL libceph: fix OOB read in decode_watchers() via missing bounds check
CVE-2026-80528 9.8 CRITICAL ceph: avoid fs reclaim while using current->journal_info
CVE-2026-80558 9.8 CRITICAL libceph: Avoid using invalid osd indices from primary_temp
CVE-2026-74752 9.8 CRITICAL sctp: validate cookie AUTH state before use
CVE-2026-80585 9.4 CRITICAL mptcp: fastopen: only mark MPTFO subflows with SYN data
CVE-2026-74751 9.4 CRITICAL riscv: lib: Fix ZBB strnlen reading past count boundary
CVE-2026-80554 9.3 CRITICAL s390/vfio_ccw: Limit the number of channel program segments
CVE-2026-80551 9.3 CRITICAL s390/vfio_ccw: Ensure first IDAW remains constant
CVE-2026-80547 8.8 HIGH s390/vfio_ccw: Implement a crw lock
CVE-2026-80553 8.8 HIGH s390/vfio_ccw: Cancel existing workqueues
CVE-2026-80576 8.8 HIGH drm/amdgpu: reject oversized IBs with per-ring packet limits

Showing top 20 of 92 CVEs. View all on vendor page &rarr; →

IV. Related Vulnerabilities

Same product: Linux
Same vendor: Linux

V. Comments for CVE-2026-74735

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