CVE-2025-40186
published 2025-11-12CVE-2025-40186: In the Linux kernel, the following vulnerability has been resolved: tcp: Don't call reqsk_fastopen_remove() in tcp_conn_request(). syzbot reported the splat…
PriorityP347high8.1CVSS 3.1
AVNACHPRNUINSUCHIHAH
EPSS
0.53%
42.0th percentile
In the Linux kernel, the following vulnerability has been resolved:
tcp: Don't call reqsk_fastopen_remove() in tcp_conn_request().
syzbot reported the splat below in tcp_conn_request(). [0]
If a listener is close()d while a TFO socket is being processed in
tcp_conn_request(), inet_csk_reqsk_queue_add() does not set reqsk->sk
and calls inet_child_forget(), which calls tcp_disconnect() for the
TFO socket.
After the cited commit, tcp_disconnect() calls reqsk_fastopen_remove(),
where reqsk_put() is called due to !reqsk->sk.
Then, reqsk_fastopen_remove() in tcp_conn_request() decrements the
last req->rsk_refcnt and frees reqsk, and __reqsk_free() at the
drop_and_free label causes the refcount underflow for the listener
and double-free of the reqsk.
Let's remove reqsk_fastopen_remove() in tcp_conn_request().
Note that other callers make sure tp->fastopen_rsk is not NULL.
[0]:
refcount_t: underflow; use-after-free.
WARNING: CPU: 12 PID: 5563 at lib/refcount.c:28 refcount_warn_saturate (lib/refcount.c:28)
Modules linked in:
CPU: 12 UID: 0 PID: 5563 Comm: syz-executor Not tainted syzkaller #0 PREEMPT(full)
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025
RIP: 0010:refcount_warn_saturate (lib/refcount.c:28)
Code: ab e8 8e b4 98 ff 0f 0b c3 cc cc cc cc cc 80 3d a4 e4 d6 01 00 75 9c c6 05 9b e4 d6 01 01 48 c7 c7 e8 df fb ab e8 6a b4 98 ff 0b e9 03 5b 76 00 cc 80 3d 7d e4 d6 01 00 0f 85 74 ff ff ff c6
RSP: 0018:ffffa79fc0304a98 EFLAGS: 00010246
RAX: d83af4db1c6b3900 RBX: ffff9f65c7a69020 RCX: d83af4db1c6b3900
RDX: 0000000000000000 RSI: 00000000ffff7fff RDI: ffffffffac78a280
RBP: 000000009d781b60 R08: 0000000000007fff R09: ffffffffac6ca280
R10: 0000000000017ffd R11: 0000000000000004 R12: ffff9f65c7b4f100
R13: ffff9f65c7d23c00 R14: ffff9f65c7d26000 R15: ffff9f65c7a64ef8
FS: 00007f9f962176c0(0000) GS:ffff9f65fcf00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000200000000180 CR3: 000000000dbbe
Affected
33 ranges· showing 25
| Vendor | Product | Version range | Fixed in |
|---|---|---|---|
| debian | linux | < linux 6.1.158-1 (bookworm) | linux 6.1.158-1 (bookworm) |
| debian | linux-6.1 | < linux 6.1.158-1 (bookworm) | linux 6.1.158-1 (bookworm) |
| linux | linux | — | — |
| linux | linux | — | — |
| linux | linux | >= 17d699727577814198d744d6afe54735c6b54c99 < 643a94b0cf767325e953591c212be2eb826b9d7f | 643a94b0cf767325e953591c212be2eb826b9d7f |
| linux | linux | >= 33a4fdf0b4a25f8ce65380c3b0136b407ca57609 < eb85ad5f23268d64b037bfb545cbcba3752f90c7 | eb85ad5f23268d64b037bfb545cbcba3752f90c7 |
| linux | linux | >= 45c8a6cc2bcd780e634a6ba8e46bffbdf1fc5c01 < 64dc47a13aa3d9daf7cec29b44dca8e22a6aea15 | 64dc47a13aa3d9daf7cec29b44dca8e22a6aea15 |
| linux | linux | >= 45c8a6cc2bcd780e634a6ba8e46bffbdf1fc5c01 < 2e7cbbbe3d61c63606994b7ff73c72537afe2e1c | 2e7cbbbe3d61c63606994b7ff73c72537afe2e1c |
| linux | linux | >= 5.10.245 < 5.10.246 | 5.10.246 |
| linux | linux | >= 5.15.194 < 5.15.195 | 5.15.195 |
| linux | linux | >= 5.4.300 < 5.4.301 | 5.4.301 |
| linux | linux | >= 6.1.154 < 6.1.157 | 6.1.157 |
| linux | linux | >= 6.12.49 < 6.12.54 | 6.12.54 |
| linux | linux | >= 6.16.9 < 6.17 | 6.17 |
| linux | linux | >= 6.6.108 < 6.6.113 | 6.6.113 |
| linux | linux | >= 7ec092a91ff351dcde89c23e795b73a328274db6 < e359b742eac1eac75cff4e38ee2e8cea492acd9b | e359b742eac1eac75cff4e38ee2e8cea492acd9b |
| linux | linux | >= a4378dedd6e07e62f2fccb17d78c9665718763d0 < ff6a8883f96a5bc74241ce5b3d431a6dcfa2124d | ff6a8883f96a5bc74241ce5b3d431a6dcfa2124d |
| linux | linux | >= dfd06131107e7b699ef1e2a24ed2f7d17c917753 < 422c1c173c39bbbae1e0eaaf8aefe40b2596233b | 422c1c173c39bbbae1e0eaaf8aefe40b2596233b |
| linux | linux | >= fa4749c065644af4db496b338452a69a3e5147d9 < c11ace909e873118295e9eb22dc8c58b0b50eb32 | c11ace909e873118295e9eb22dc8c58b0b50eb32 |
| linux | linux_kernel | >= 0 < 5.10.247-1 | 5.10.247-1 |
| linux | linux_kernel | >= 0 < 6.1.158-1 | 6.1.158-1 |
| linux | linux_kernel | >= 0 < 6.12.57-1 | 6.12.57-1 |
| linux | linux_kernel | >= 0 < 6.17.6-1 | 6.17.6-1 |
| linux | linux_kernel | >= 0 < 5.4.301 | 5.4.301 |
| linux | linux_kernel | >= 0 < 6.17.0-14.14 | 6.17.0-14.14 |
CVSS provenance
nvdv3.18.1HIGHCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
vendor_redhat7.0HIGH
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OSV
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GHSA
GHSA-qx52-pj36-489j: In the Linux kernel, the following vulnerability has been resolved:
tcp: Don't call reqsk_fastopen_remove() in tcp_conn_request()
ghsa_unreviewed·2025-11-13
CVE-2025-40186 GHSA-qx52-pj36-489j: In the Linux kernel, the following vulnerability has been resolved:
tcp: Don't call reqsk_fastopen_remove() in tcp_conn_request()
In the Linux kernel, the following vulnerability has been resolved:
tcp: Don't call reqsk_fastopen_remove() in tcp_conn_request().
syzbot reported the splat below in tcp_conn_request(). [0]
If a listener is close()d while a TFO socket is being processed in
tcp_conn_request(), inet_csk_reqsk_queue_add() does not set reqsk->sk
and calls inet_child_forget(), which calls tcp_disconnect() for the
TFO socket.
After the cited commit, tcp_disconnect() calls reqsk_fastopen_remove(),
where reqsk_put() is called due to !reqsk->sk.
Then, reqsk_fastopen_remove() in tcp_conn_request() decrements the
last req->rsk_refcnt and frees reqsk, and __reqsk_free() at the
drop_and_free label causes the refcount underflow for the listener
and double-free of the reqsk.
Let's remove reqsk_fastopen_remove() in
OSV
tcp: Don't call reqsk_fastopen_remove() in tcp_conn_request().
osv·2025-11-12
CVE-2025-40186 tcp: Don't call reqsk_fastopen_remove() in tcp_conn_request().
tcp: Don't call reqsk_fastopen_remove() in tcp_conn_request().
In the Linux kernel, the following vulnerability has been resolved:
tcp: Don't call reqsk_fastopen_remove() in tcp_conn_request().
syzbot reported the splat below in tcp_conn_request(). [0]
If a listener is close()d while a TFO socket is being processed in
tcp_conn_request(), inet_csk_reqsk_queue_add() does not set reqsk->sk
and calls inet_child_forget(), which calls tcp_disconnect() for the
TFO socket.
After the cited commit, tcp_disconnect() calls reqsk_fastopen_remove(),
where reqsk_put() is called due to !reqsk->sk.
Then, reqsk_fastopen_remove() in tcp_conn_request() decrements the
last req->rsk_refcnt and frees reqsk, and __reqsk_free() at the
drop_and_free label causes the refcount underflow for the listener
and dou
OSV
CVE-2025-40186: In the Linux kernel, the following vulnerability has been resolved: tcp: Don't call reqsk_fastopen_remove() in tcp_conn_request()
osv·2025-11-12
CVE-2025-40186 CVE-2025-40186: In the Linux kernel, the following vulnerability has been resolved: tcp: Don't call reqsk_fastopen_remove() in tcp_conn_request()
In the Linux kernel, the following vulnerability has been resolved: tcp: Don't call reqsk_fastopen_remove() in tcp_conn_request(). syzbot reported the splat below in tcp_conn_request(). [0] If a listener is close()d while a TFO socket is being processed in tcp_conn_request(), inet_csk_reqsk_queue_add() does not set reqsk->sk and calls inet_child_forget(), which calls tcp_disconnect() for the TFO socket. After the cited commit, tcp_disconnect() calls reqsk_fastopen_remove(), where reqsk_put() is called due to !reqsk->sk. Then, reqsk_fastopen_remove() in tcp_conn_request() decrements the last req->rsk_refcnt and frees reqsk, and __reqsk_free() at the drop_and_free label causes the refcount underflow for the listener and double-free of the reqsk. Let's remove reqsk_fastopen_remove() in tcp_co
Ubuntu
Linux kernel (Azure) vulnerabilities
vendor_ubuntu·2026-02-24
CVE-2025-40175 Linux kernel (Azure) vulnerabilities
Title: Linux kernel (Azure) vulnerabilities
Summary: Several security issues were fixed in the Linux kernel.
Several security issues were discovered in the Linux kernel.
An attacker could possibly use these to compromise the system.
This update corrects flaws in the following subsystems:
- ARM64 architecture;
- MIPS architecture;
- Nios II architecture;
- PA-RISC architecture;
- RISC-V architecture;
- S390 architecture;
- Sun Sparc architecture;
- x86 architecture;
- Xtensa architecture;
- Block layer subsystem;
- Cryptographic API;
- Compute Acceleration Framework;
- ACPI drivers;
- Drivers core;
- Network block device driver;
- Bluetooth drivers;
- Bus devices;
- Hardware random number generator core;
- Character device driver;
- Clock framework and drivers;
- Data acquisition framewor
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vendor_ubuntu·2026-02-17
CVE-2025-40304 Linux kernel vulnerabilities
Title: Linux kernel vulnerabilities
Summary: Several security issues were fixed in the Linux kernel.
Several security issues were discovered in the Linux kernel.
An attacker could possibly use these to compromise the system.
This update corrects flaws in the following subsystems:
- ARM64 architecture;
- MIPS architecture;
- Nios II architecture;
- PA-RISC architecture;
- RISC-V architecture;
- S390 architecture;
- Sun Sparc architecture;
- x86 architecture;
- Xtensa architecture;
- Block layer subsystem;
- Cryptographic API;
- Compute Acceleration Framework;
- ACPI drivers;
- Drivers core;
- Network block device driver;
- Bluetooth drivers;
- Bus devices;
- Hardware random number generator core;
- Character device driver;
- Clock framework and drivers;
- Data acquisition framework and dr
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vendor_ubuntu·2026-02-17
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Title: Linux kernel (OEM) vulnerabilities
Summary: Several security issues were fixed in the Linux kernel.
Several security issues were discovered in the Linux kernel.
An attacker could possibly use these to compromise the system.
This update corrects flaws in the following subsystems:
- ARM64 architecture;
- MIPS architecture;
- Nios II architecture;
- PA-RISC architecture;
- RISC-V architecture;
- S390 architecture;
- Sun Sparc architecture;
- x86 architecture;
- Xtensa architecture;
- Block layer subsystem;
- Cryptographic API;
- Compute Acceleration Framework;
- ACPI drivers;
- Drivers core;
- Network block device driver;
- Bluetooth drivers;
- Bus devices;
- Hardware random number generator core;
- Character device driver;
- Clock framework and drivers;
- Data acquisition framework
Ubuntu
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vendor_ubuntu·2026-02-12
CVE-2025-68242 Linux kernel (GCP) vulnerabilities
Title: Linux kernel (GCP) vulnerabilities
Summary: Several security issues were fixed in the Linux kernel.
Several security issues were discovered in the Linux kernel.
An attacker could possibly use these to compromise the system.
This update corrects flaws in the following subsystems:
- ARM64 architecture;
- MIPS architecture;
- Nios II architecture;
- PA-RISC architecture;
- RISC-V architecture;
- S390 architecture;
- Sun Sparc architecture;
- x86 architecture;
- Xtensa architecture;
- Block layer subsystem;
- Cryptographic API;
- Compute Acceleration Framework;
- ACPI drivers;
- Drivers core;
- Network block device driver;
- Bluetooth drivers;
- Bus devices;
- Hardware random number generator core;
- Character device driver;
- Clock framework and drivers;
- Data acquisition framework
Ubuntu
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vendor_ubuntu·2026-02-12
CVE-2025-40304 Linux kernel vulnerabilities
Title: Linux kernel vulnerabilities
Summary: Several security issues were fixed in the Linux kernel.
Several security issues were discovered in the Linux kernel.
An attacker could possibly use these to compromise the system.
This update corrects flaws in the following subsystems:
- ARM64 architecture;
- MIPS architecture;
- Nios II architecture;
- PA-RISC architecture;
- RISC-V architecture;
- S390 architecture;
- Sun Sparc architecture;
- x86 architecture;
- Xtensa architecture;
- Block layer subsystem;
- Cryptographic API;
- Compute Acceleration Framework;
- ACPI drivers;
- Drivers core;
- Network block device driver;
- Bluetooth drivers;
- Bus devices;
- Hardware random number generator core;
- Character device driver;
- Clock framework and drivers;
- Data acquisition framework and dr
Red Hat
kernel: Linux kernel: Privilege escalation or Denial of Service via TCP Fast Open vulnerability
vendor_redhat·2025-11-12·CVSS 7.0
CVE-2025-40186 [HIGH] CWE-826 kernel: Linux kernel: Privilege escalation or Denial of Service via TCP Fast Open vulnerability
kernel: Linux kernel: Privilege escalation or Denial of Service via TCP Fast Open vulnerability
In the Linux kernel, the following vulnerability has been resolved:
tcp: Don't call reqsk_fastopen_remove() in tcp_conn_request().
syzbot reported the splat below in tcp_conn_request(). [0]
If a listener is close()d while a TFO socket is being processed in
tcp_conn_request(), inet_csk_reqsk_queue_add() does not set reqsk->sk
and calls inet_child_forget(), which calls tcp_disconnect() for the
TFO socket.
After the cited commit, tcp_disconnect() calls reqsk_fastopen_remove(),
where reqsk_put() is called due to !reqsk->sk.
Then, reqsk_fastopen_remove() in tcp_conn_request() decrements the
last req->rsk_refcnt and frees reqsk, and __reqsk_free() at the
drop_and_free label causes the refcount underf
Debian
CVE-2025-40186: linux - In the Linux kernel, the following vulnerability has been resolved: tcp: Don't ...
vendor_debian·2025
CVE-2025-40186 CVE-2025-40186: linux - In the Linux kernel, the following vulnerability has been resolved: tcp: Don't ...
In the Linux kernel, the following vulnerability has been resolved: tcp: Don't call reqsk_fastopen_remove() in tcp_conn_request(). syzbot reported the splat below in tcp_conn_request(). [0] If a listener is close()d while a TFO socket is being processed in tcp_conn_request(), inet_csk_reqsk_queue_add() does not set reqsk->sk and calls inet_child_forget(), which calls tcp_disconnect() for the TFO socket. After the cited commit, tcp_disconnect() calls reqsk_fastopen_remove(), where reqsk_put() is called due to !reqsk->sk. Then, reqsk_fastopen_remove() in tcp_conn_request() decrements the last req->rsk_refcnt and frees reqsk, and __reqsk_free() at the drop_and_free label causes the refcount underflow for the listener and double-free of the reqsk. Let's remove reqsk_fastopen_remove() in tcp_co
No detection rules found.
No public exploits indexed.
https://git.kernel.org/stable/c/2e7cbbbe3d61c63606994b7ff73c72537afe2e1chttps://git.kernel.org/stable/c/422c1c173c39bbbae1e0eaaf8aefe40b2596233bhttps://git.kernel.org/stable/c/643a94b0cf767325e953591c212be2eb826b9d7fhttps://git.kernel.org/stable/c/64dc47a13aa3d9daf7cec29b44dca8e22a6aea15https://git.kernel.org/stable/c/c11ace909e873118295e9eb22dc8c58b0b50eb32https://git.kernel.org/stable/c/e359b742eac1eac75cff4e38ee2e8cea492acd9bhttps://git.kernel.org/stable/c/eb85ad5f23268d64b037bfb545cbcba3752f90c7https://git.kernel.org/stable/c/ff6a8883f96a5bc74241ce5b3d431a6dcfa2124d
2025-11-12
Published