CVE-2025-39955 (GCVE-0-2025-39955)
Vulnerability from cvelistv5
Published
2025-10-09 09:47
Modified
2025-10-09 09:47
Severity ?
VLAI Severity ?
EPSS score ?
Summary
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 a new client before
the TFO socket completes 3WHS:
1. accept()
2. connect(AF_UNSPEC)
3. connect() to another destination
As of accept(), sk->sk_state is TCP_SYN_RECV, and tcp_disconnect() changes
it to TCP_CLOSE and makes connect() possible, which restarts timers.
Since tcp_disconnect() forgot to clear tcp_sk(sk)->fastopen_rsk, the
retransmit timer triggered the warning and the intended packet was not
retransmitted.
Let's call reqsk_fastopen_remove() in tcp_disconnect().
[0]:
WARNING: CPU: 2 PID: 0 at net/ipv4/tcp_timer.c:542 tcp_retransmit_timer (net/ipv4/tcp_timer.c:542 (discriminator 7))
Modules linked in:
CPU: 2 UID: 0 PID: 0 Comm: swapper/2 Not tainted 6.17.0-rc5-g201825fb4278 #62 PREEMPT(voluntary)
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
RIP: 0010:tcp_retransmit_timer (net/ipv4/tcp_timer.c:542 (discriminator 7))
Code: 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 <0f> 0b 90 48 8b 85 c0 00 00 00 48 89 ef 48 8b 40 30 e8 6a 4f 06 3e
RSP: 0018:ffffc900002f8d40 EFLAGS: 00010293
RAX: 0000000000000002 RBX: ffff888106911400 RCX: 0000000000000017
RDX: 0000000002517619 RSI: ffffffff83764080 RDI: ffff888106911400
RBP: ffff888106d5c000 R08: 0000000000000001 R09: ffffc900002f8de8
R10: 00000000000000c2 R11: ffffc900002f8ff8 R12: ffff888106911540
R13: ffff888106911480 R14: ffff888106911840 R15: ffffc900002f8de0
FS: 0000000000000000(0000) GS:ffff88907b768000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f8044d69d90 CR3: 0000000002c30003 CR4: 0000000000370ef0
Call Trace:
<IRQ>
tcp_write_timer (net/ipv4/tcp_timer.c:738)
call_timer_fn (kernel/time/timer.c:1747)
__run_timers (kernel/time/timer.c:1799 kernel/time/timer.c:2372)
timer_expire_remote (kernel/time/timer.c:2385 kernel/time/timer.c:2376 kernel/time/timer.c:2135)
tmigr_handle_remote_up (kernel/time/timer_migration.c:944 kernel/time/timer_migration.c:1035)
__walk_groups.isra.0 (kernel/time/timer_migration.c:533 (discriminator 1))
tmigr_handle_remote (kernel/time/timer_migration.c:1096)
handle_softirqs (./arch/x86/include/asm/jump_label.h:36 ./include/trace/events/irq.h:142 kernel/softirq.c:580)
irq_exit_rcu (kernel/softirq.c:614 kernel/softirq.c:453 kernel/softirq.c:680 kernel/softirq.c:696)
sysvec_apic_timer_interrupt (arch/x86/kernel/apic/apic.c:1050 (discriminator 35) arch/x86/kernel/apic/apic.c:1050 (discriminator 35))
</IRQ>
References
Impacted products
| Vendor | Product | Version | ||
|---|---|---|---|---|
| Linux | Linux |
Version: 8336886f786fdacbc19b719c1f7ea91eb70706d4 Version: 8336886f786fdacbc19b719c1f7ea91eb70706d4 Version: 8336886f786fdacbc19b719c1f7ea91eb70706d4 Version: 8336886f786fdacbc19b719c1f7ea91eb70706d4 Version: 8336886f786fdacbc19b719c1f7ea91eb70706d4 Version: 8336886f786fdacbc19b719c1f7ea91eb70706d4 Version: 8336886f786fdacbc19b719c1f7ea91eb70706d4 Version: 8336886f786fdacbc19b719c1f7ea91eb70706d4 |
||
{
"containers": {
"cna": {
"affected": [
{
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"product": "Linux",
"programFiles": [
"net/ipv4/tcp.c"
],
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"vendor": "Linux",
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"vendor": "Linux",
"versions": [
{
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"version": "3.7"
},
{
"lessThan": "3.7",
"status": "unaffected",
"version": "0",
"versionType": "semver"
},
{
"lessThanOrEqual": "5.4.*",
"status": "unaffected",
"version": "5.4.300",
"versionType": "semver"
},
{
"lessThanOrEqual": "5.10.*",
"status": "unaffected",
"version": "5.10.245",
"versionType": "semver"
},
{
"lessThanOrEqual": "5.15.*",
"status": "unaffected",
"version": "5.15.194",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.1.*",
"status": "unaffected",
"version": "6.1.154",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.6.*",
"status": "unaffected",
"version": "6.6.108",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.12.*",
"status": "unaffected",
"version": "6.12.49",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.16.*",
"status": "unaffected",
"version": "6.16.9",
"versionType": "semver"
},
{
"lessThanOrEqual": "*",
"status": "unaffected",
"version": "6.17",
"versionType": "original_commit_for_fix"
}
]
}
],
"cpeApplicability": [
{
"nodes": [
{
"cpeMatch": [
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "5.4.300",
"versionStartIncluding": "3.7",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "5.10.245",
"versionStartIncluding": "3.7",
"vulnerable": true
},
{
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{
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"versionEndExcluding": "6.1.154",
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"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "6.6.108",
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},
{
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{
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}
],
"negate": false,
"operator": "OR"
}
]
}
],
"descriptions": [
{
"lang": "en",
"value": "In the Linux kernel, the following vulnerability has been resolved:\n\ntcp: Clear tcp_sk(sk)-\u003efastopen_rsk in tcp_disconnect().\n\nsyzbot reported the splat below where a socket had tcp_sk(sk)-\u003efastopen_rsk\nin the TCP_ESTABLISHED state. [0]\n\nsyzbot reused the server-side TCP Fast Open socket as a new client before\nthe TFO socket completes 3WHS:\n\n 1. accept()\n 2. connect(AF_UNSPEC)\n 3. connect() to another destination\n\nAs of accept(), sk-\u003esk_state is TCP_SYN_RECV, and tcp_disconnect() changes\nit to TCP_CLOSE and makes connect() possible, which restarts timers.\n\nSince tcp_disconnect() forgot to clear tcp_sk(sk)-\u003efastopen_rsk, the\nretransmit timer triggered the warning and the intended packet was not\nretransmitted.\n\nLet\u0027s call reqsk_fastopen_remove() in tcp_disconnect().\n\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 \u003c0f\u003e 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:\n \u003cIRQ\u003e\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))\n \u003c/IRQ\u003e"
}
],
"providerMetadata": {
"dateUpdated": "2025-10-09T09:47:33.556Z",
"orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"shortName": "Linux"
},
"references": [
{
"url": "https://git.kernel.org/stable/c/7ec092a91ff351dcde89c23e795b73a328274db6"
},
{
"url": "https://git.kernel.org/stable/c/a4378dedd6e07e62f2fccb17d78c9665718763d0"
},
{
"url": "https://git.kernel.org/stable/c/33a4fdf0b4a25f8ce65380c3b0136b407ca57609"
},
{
"url": "https://git.kernel.org/stable/c/17d699727577814198d744d6afe54735c6b54c99"
},
{
"url": "https://git.kernel.org/stable/c/dfd06131107e7b699ef1e2a24ed2f7d17c917753"
},
{
"url": "https://git.kernel.org/stable/c/fa4749c065644af4db496b338452a69a3e5147d9"
},
{
"url": "https://git.kernel.org/stable/c/ae313d14b45eca7a6bb29cb9bf396d977e7d28fb"
},
{
"url": "https://git.kernel.org/stable/c/45c8a6cc2bcd780e634a6ba8e46bffbdf1fc5c01"
}
],
"title": "tcp: Clear tcp_sk(sk)-\u003efastopen_rsk in tcp_disconnect().",
"x_generator": {
"engine": "bippy-1.2.0"
}
}
},
"cveMetadata": {
"assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"assignerShortName": "Linux",
"cveId": "CVE-2025-39955",
"datePublished": "2025-10-09T09:47:33.556Z",
"dateReserved": "2025-04-16T07:20:57.149Z",
"dateUpdated": "2025-10-09T09:47:33.556Z",
"state": "PUBLISHED"
},
"dataType": "CVE_RECORD",
"dataVersion": "5.1",
"vulnerability-lookup:meta": {
"nvd": "{\"cve\":{\"id\":\"CVE-2025-39955\",\"sourceIdentifier\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"published\":\"2025-10-09T10:15:36.220\",\"lastModified\":\"2025-10-09T15:50:04.013\",\"vulnStatus\":\"Awaiting Analysis\",\"cveTags\":[],\"descriptions\":[{\"lang\":\"en\",\"value\":\"In the Linux kernel, the following vulnerability has been resolved:\\n\\ntcp: Clear tcp_sk(sk)-\u003efastopen_rsk in tcp_disconnect().\\n\\nsyzbot reported the splat below where a socket had tcp_sk(sk)-\u003efastopen_rsk\\nin the TCP_ESTABLISHED state. [0]\\n\\nsyzbot reused the server-side TCP Fast Open socket as a new client before\\nthe TFO socket completes 3WHS:\\n\\n 1. accept()\\n 2. connect(AF_UNSPEC)\\n 3. connect() to another destination\\n\\nAs of accept(), sk-\u003esk_state is TCP_SYN_RECV, and tcp_disconnect() changes\\nit to TCP_CLOSE and makes connect() possible, which restarts timers.\\n\\nSince tcp_disconnect() forgot to clear tcp_sk(sk)-\u003efastopen_rsk, the\\nretransmit timer triggered the warning and the intended packet was not\\nretransmitted.\\n\\nLet\u0027s call reqsk_fastopen_remove() in tcp_disconnect().\\n\\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 \u003c0f\u003e 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:\\n \u003cIRQ\u003e\\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))\\n \u003c/IRQ\u003e\"}],\"metrics\":{},\"references\":[{\"url\":\"https://git.kernel.org/stable/c/17d699727577814198d744d6afe54735c6b54c99\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/33a4fdf0b4a25f8ce65380c3b0136b407ca57609\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/45c8a6cc2bcd780e634a6ba8e46bffbdf1fc5c01\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/7ec092a91ff351dcde89c23e795b73a328274db6\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/a4378dedd6e07e62f2fccb17d78c9665718763d0\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/ae313d14b45eca7a6bb29cb9bf396d977e7d28fb\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/dfd06131107e7b699ef1e2a24ed2f7d17c917753\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/fa4749c065644af4db496b338452a69a3e5147d9\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"}]}}"
}
}
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Sightings
| Author | Source | Type | Date |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or seen somewhere by the user.
- Confirmed: The vulnerability is confirmed from an analyst perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: This vulnerability was exploited and seen by the user reporting the sighting.
- Patched: This vulnerability was successfully patched by the user reporting the sighting.
- Not exploited: This vulnerability was not exploited or seen by the user reporting the sighting.
- Not confirmed: The user expresses doubt about the veracity of the vulnerability.
- Not patched: This vulnerability was not successfully patched by the user reporting the sighting.
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