tcp: Don't call reqsk_fastopen_remove() in tcp_conn_request().

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2025-40186
StatePUBLISHED
AssignerLinux
Source PriorityCVE Program / NVD first with legacy fallback
Published2025-11-12 22:15:45 UTC
Updated2026-07-30 06:24:16 UTC
DescriptionIn 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 <0f> 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: 000000000dbbe006 CR4: 0000000000372ef0 Call Trace: <IRQ> tcp_conn_request (./include/linux/refcount.h:400 ./include/linux/refcount.h:432 ./include/linux/refcount.h:450 ./include/net/sock.h:1965 ./include/net/request_sock.h:131 net/ipv4/tcp_input.c:7301) tcp_rcv_state_process (net/ipv4/tcp_input.c:6708) tcp_v6_do_rcv (net/ipv6/tcp_ipv6.c:1670) tcp_v6_rcv (net/ipv6/tcp_ipv6.c:1906) ip6_protocol_deliver_rcu (net/ipv6/ip6_input.c:438) ip6_input (net/ipv6/ip6_input.c:500) ipv6_rcv (net/ipv6/ip6_input.c:311) __netif_receive_skb (net/core/dev.c:6104) process_backlog (net/core/dev.c:6456) __napi_poll (net/core/dev.c:7506) net_rx_action (net/core/dev.c:7569 net/core/dev.c:7696) handle_softirqs (kernel/softirq.c:579) do_softirq (kernel/softirq.c:480) </IRQ>

Risk And Classification

Primary CVSS: v3.1 8.1 HIGH from 416baaa9-dc9f-4396-8d5f-8c081fb06d67

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

EPSS: 0.005330000 probability, percentile 0.420190000 (date 2026-07-31)

VersionSourceTypeScoreSeverityVector
3.1416baaa9-dc9f-4396-8d5f-8c081fb06d67Secondary8.1HIGHCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
3.1CNADECLARED8.1HIGHCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
High
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

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

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Linux Linux affected 7ec092a91ff351dcde89c23e795b73a328274db6 e359b742eac1eac75cff4e38ee2e8cea492acd9b git Not specified
CNA Linux Linux affected a4378dedd6e07e62f2fccb17d78c9665718763d0 ff6a8883f96a5bc74241ce5b3d431a6dcfa2124d git Not specified
CNA Linux Linux affected 33a4fdf0b4a25f8ce65380c3b0136b407ca57609 eb85ad5f23268d64b037bfb545cbcba3752f90c7 git Not specified
CNA Linux Linux affected 17d699727577814198d744d6afe54735c6b54c99 643a94b0cf767325e953591c212be2eb826b9d7f git Not specified
CNA Linux Linux affected dfd06131107e7b699ef1e2a24ed2f7d17c917753 422c1c173c39bbbae1e0eaaf8aefe40b2596233b git Not specified
CNA Linux Linux affected fa4749c065644af4db496b338452a69a3e5147d9 c11ace909e873118295e9eb22dc8c58b0b50eb32 git Not specified
CNA Linux Linux affected 45c8a6cc2bcd780e634a6ba8e46bffbdf1fc5c01 64dc47a13aa3d9daf7cec29b44dca8e22a6aea15 git Not specified
CNA Linux Linux affected 45c8a6cc2bcd780e634a6ba8e46bffbdf1fc5c01 2e7cbbbe3d61c63606994b7ff73c72537afe2e1c git Not specified
CNA Linux Linux affected ae313d14b45eca7a6bb29cb9bf396d977e7d28fb git Not specified
CNA Linux Linux affected 5.4.300 5.4.301 semver Not specified
CNA Linux Linux affected 5.10.245 5.10.246 semver Not specified
CNA Linux Linux affected 5.15.194 5.15.195 semver Not specified
CNA Linux Linux affected 6.1.154 6.1.157 semver Not specified
CNA Linux Linux affected 6.6.108 6.6.113 semver Not specified
CNA Linux Linux affected 6.12.49 6.12.54 semver Not specified
CNA Linux Linux affected 6.16.9 6.17 semver Not specified
CNA Linux Linux affected 6.17 Not specified
CNA Linux Linux unaffected 6.17 semver Not specified
CNA Linux Linux unaffected 5.4.301 5.4.* semver Not specified
CNA Linux Linux unaffected 5.10.246 5.10.* semver Not specified
CNA Linux Linux unaffected 5.15.195 5.15.* semver Not specified
CNA Linux Linux unaffected 6.1.157 6.1.* semver Not specified
CNA Linux Linux unaffected 6.6.113 6.6.* semver Not specified
CNA Linux Linux unaffected 6.12.54 6.12.* semver Not specified
CNA Linux Linux unaffected 6.17.4 6.17.* semver Not specified
CNA Linux Linux unaffected 6.18 * original_commit_for_fix Not specified

References

ReferenceSourceLinkTags
git.kernel.org/stable/c/ff6a8883f96a5bc74241ce5b3d431a6dcfa2124d 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/64dc47a13aa3d9daf7cec29b44dca8e22a6aea15 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/643a94b0cf767325e953591c212be2eb826b9d7f 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/e359b742eac1eac75cff4e38ee2e8cea492acd9b 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/2e7cbbbe3d61c63606994b7ff73c72537afe2e1c 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/422c1c173c39bbbae1e0eaaf8aefe40b2596233b 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/c11ace909e873118295e9eb22dc8c58b0b50eb32 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/eb85ad5f23268d64b037bfb545cbcba3752f90c7 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
CVE Program record CVE.ORG www.cve.org canonical
NVD vulnerability detail NVD nvd.nist.gov canonical, analysis

© CVE.report 2026

Use of this information constitutes acceptance for use in an AS IS condition. There are NO warranties, implied or otherwise, with regard to this information or its use. Any use of this information is at the user's risk. It is the responsibility of user to evaluate the accuracy, completeness or usefulness of any information, opinion, advice or other content. EACH USER WILL BE SOLELY RESPONSIBLE FOR ANY consequences of his or her direct or indirect use of this web site. ALL WARRANTIES OF ANY KIND ARE EXPRESSLY DISCLAIMED. This site will NOT BE LIABLE FOR ANY DIRECT, INDIRECT or any other kind of loss.

CVE, CWE, and OVAL are registred trademarks of The MITRE Corporation and the authoritative source of CVE content is MITRE's CVE web site. This site includes MITRE data granted under the following license.

Free CVE JSON API cve.report/api

CVE.report and Source URL Uptime Status status.cve.report