CVE ID : CVE-2025-39955<\/p>\n
Published : Oct. 9, 2025, 10:15 a.m. | 22\u00a0minutes ago<\/p>\n
Description : In the Linux kernel, the following vulnerability has been resolved:<\/p>\n
tcp: Clear tcp_sk(sk)->fastopen_rsk in tcp_disconnect().<\/p>\n
syzbot reported the splat below where a socket had tcp_sk(sk)->fastopen_rsk
\nin the TCP_ESTABLISHED state. [0]\n
syzbot reused the server-side TCP Fast Open socket as a new client before
\nthe TFO socket completes 3WHS:<\/p>\n
1. accept()
\n 2. connect(AF_UNSPEC)
\n 3. connect() to another destination<\/p>\n
As of accept(), sk->sk_state is TCP_SYN_RECV, and tcp_disconnect() changes
\nit to TCP_CLOSE and makes connect() possible, which restarts timers.<\/p>\n
Since tcp_disconnect() forgot to clear tcp_sk(sk)->fastopen_rsk, the
\nretransmit timer triggered the warning and the intended packet was not
\nretransmitted.<\/p>\n
Let’s call reqsk_fastopen_remove() in tcp_disconnect().<\/p>\n[0]:
\nWARNING: CPU: 2 PID: 0 at net\/ipv4\/tcp_timer.c:542 tcp_retransmit_timer (net\/ipv4\/tcp_timer.c:542 (discriminator 7))
\nModules linked in:
\nCPU: 2 UID: 0 PID: 0 Comm: swapper\/2 Not tainted 6.17.0-rc5-g201825fb4278 #62 PREEMPT(voluntary)
\nHardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.3-debian-1.16.3-2 04\/01\/2014
\nRIP: 0010:tcp_retransmit_timer (net\/ipv4\/tcp_timer.c:542 (discriminator 7))
\nCode: 41 55 41 54 55 53 48 8b af b8 08 00 00 48 89 fb 48 85 ed 0f 84 55 01 00 00 0f b6 47 12 3c 03 74 0c 0f b6 47 12 3c 04 74 04 90 0b 90 48 8b 85 c0 00 00 00 48 89 ef 48 8b 40 30 e8 6a 4f 06 3e
\nRSP: 0018:ffffc900002f8d40 EFLAGS: 00010293
\nRAX: 0000000000000002 RBX: ffff888106911400 RCX: 0000000000000017
\nRDX: 0000000002517619 RSI: ffffffff83764080 RDI: ffff888106911400
\nRBP: ffff888106d5c000 R08: 0000000000000001 R09: ffffc900002f8de8
\nR10: 00000000000000c2 R11: ffffc900002f8ff8 R12: ffff888106911540
\nR13: ffff888106911480 R14: ffff888106911840 R15: ffffc900002f8de0
\nFS: 0000000000000000(0000) GS:ffff88907b768000(0000) knlGS:0000000000000000
\nCS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
\nCR2: 00007f8044d69d90 CR3: 0000000002c30003 CR4: 0000000000370ef0
\nCall Trace:<\/p>\n
tcp_write_timer (net\/ipv4\/tcp_timer.c:738)
\n call_timer_fn (kernel\/time\/timer.c:1747)
\n __run_timers (kernel\/time\/timer.c:1799 kernel\/time\/timer.c:2372)
\n timer_expire_remote (kernel\/time\/timer.c:2385 kernel\/time\/timer.c:2376 kernel\/time\/timer.c:2135)
\n tmigr_handle_remote_up (kernel\/time\/timer_migration.c:944 kernel\/time\/timer_migration.c:1035)
\n __walk_groups.isra.0 (kernel\/time\/timer_migration.c:533 (discriminator 1))
\n tmigr_handle_remote (kernel\/time\/timer_migration.c:1096)
\n handle_softirqs (.\/arch\/x86\/include\/asm\/jump_label.h:36 .\/include\/trace\/events\/irq.h:142 kernel\/softirq.c:580)
\n irq_exit_rcu (kernel\/softirq.c:614 kernel\/softirq.c:453 kernel\/softirq.c:680 kernel\/softirq.c:696)
\n sysvec_apic_timer_interrupt (arch\/x86\/kernel\/apic\/apic.c:1050 (discriminator 35) arch\/x86\/kernel\/apic\/apic.c:1050 (discriminator 35))<\/p>\n
Severity: 0.0 | NA<\/p>\n
Visit the link for more details, such as CVSS details, affected products, timeline, and more…\u00a0<\/p>\n","protected":false},"excerpt":{"rendered":"
CVE ID : CVE-2025-39955 Published : Oct. 9, 2025, 10:15 a.m. | 22\u00a0minutes ago Description : In the Linux kernel, the following vulnerability has been resolved: tcp: Clear tcp_sk(sk)->fastopen_rsk in tcp_disconnect(). syzbot reported the splat below where a socket had tcp_sk(sk)->fastopen_rsk in the TCP_ESTABLISHED state. [0] syzbot reused the server-side TCP Fast Open socket as …<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[26],"tags":[],"class_list":["post-71284","post","type-post","status-publish","format-standard","hentry","category-vulnerability"],"_links":{"self":[{"href":"https:\/\/afaghhosting.net\/blog\/wp-json\/wp\/v2\/posts\/71284","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/afaghhosting.net\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/afaghhosting.net\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/afaghhosting.net\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/afaghhosting.net\/blog\/wp-json\/wp\/v2\/comments?post=71284"}],"version-history":[{"count":0,"href":"https:\/\/afaghhosting.net\/blog\/wp-json\/wp\/v2\/posts\/71284\/revisions"}],"wp:attachment":[{"href":"https:\/\/afaghhosting.net\/blog\/wp-json\/wp\/v2\/media?parent=71284"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/afaghhosting.net\/blog\/wp-json\/wp\/v2\/categories?post=71284"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/afaghhosting.net\/blog\/wp-json\/wp\/v2\/tags?post=71284"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}