CVE-2024-36889
Status: AnalyzedMedium (5.5)—
In the Linux kernel, the following vulnerability has been resolved:
mptcp: ensure snd_nxt is properly initialized on connect
Christoph reported a splat hinting at a corrupted snd_una:
When fallback to TCP happens early on a client socket, snd_nxt is not yet initialized and any incoming ack will copy such value into snd_una. If the mptcp worker (dumbly) tries mptcp-level re-injection after such ack, that would unconditionally trigger a send buffer cleanup using 'bad' snd_una values.
We could easily disable re-injection for fallback sockets, but such dumb behavior already helped catching a few subtle issues and a very low to zero impact in practice.
Read full descriptionShow less
Instead address the issue always initializing snd_nxt (and write_seq, for consistency) at connect time.
Technical details traces, logs and code from the original report
WARNING: CPU: 1 PID: 38 at net/mptcp/protocol.c:1005 __mptcp_clean_una+0x4b3/0x620 net/mptcp/protocol.c:1005 Modules linked in: CPU: 1 PID: 38 Comm: kworker/1:1 Not tainted 6.9.0-rc1-gbbeac67456c9 #59 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.11.0-2.el7 04/01/2014 Workqueue: events mptcp_worker RIP: 0010:__mptcp_clean_una+0x4b3/0x620 net/mptcp/protocol.c:1005 Code: be 06 01 00 00 bf 06 01 00 00 e8 a8 12 e7 fe e9 00 fe ff ff e8 8e 1a e7 fe 0f b7 ab 3e 02 00 00 e9 d3 fd ff ff e8 7d 1a e7 fe <0f> 0b 4c 8b bb e0 05 00 00 e9 74 fc ff ff e8 6a 1a e7 fe 0f 0b e9 RSP: 0018:ffffc9000013fd48 EFLAGS: 00010293 RAX: 0000000000000000 RBX: ffff8881029bd280 RCX: ffffffff82382fe4 RDX: ffff8881003cbd00 RSI: ffffffff823833c3 RDI: 0000000000000001 RBP: 0000000000000000 R08: 0000000000000001 R09: 0000000000000000 R10: 0000000000000000 R11: fefefefefefefeff R12: ffff888138ba8000 R13: 0000000000000106 R14: ffff8881029bd908 R15: ffff888126560000 FS: 0000000000000000(0000) GS:ffff88813bd00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007f604a5dae38 CR3: 0000000101dac002 CR4: 0000000000170ef0 Call Trace: <TASK> __mptcp_clean_una_wakeup net/mptcp/protocol.c:1055 [inline] mptcp_clean_una_wakeup net/mptcp/protocol.c:1062 [inline] __mptcp_retrans+0x7f/0x7e0 net/mptcp/protocol.c:2615 mptcp_worker+0x434/0x740 net/mptcp/protocol.c:2767 process_one_work+0x1e0/0x560 kernel/workqueue.c:3254 process_scheduled_works kernel/workqueue.c:3335 [inline] worker_thread+0x3c7/0x640 kernel/workqueue.c:3416 kthread+0x121/0x170 kernel/kthread.c:388 ret_from_fork+0x44/0x50 arch/x86/kernel/process.c:147 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:243 </TASK>
CVSS
- Version: 3.1
- Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
- Base score: 5.5
Exploitation probability (EPSS)
- Probability of exploitation in the next 30 days: 0.27%
- Percentile among all scored CVEs: 17
- Score date: 10/8/2026
EPSS (Exploit Prediction Scoring System, FIRST) estimates how likely a vulnerability is to be exploited in the wild within 30 days. It complements CVSS (impact) and CISA KEV (confirmed exploitation).
Affected technologies (2)
CWEs
- NVD-CWE-noinfo
References
- https://git.kernel.org/stable/c/39ca83ed73db9edcc6d70c0dc7a73085a4725012
- https://git.kernel.org/stable/c/592f69b41766d366dbb8ff4ef5a67c4396527bbe
- https://git.kernel.org/stable/c/99951b62bf20cec9247f633a3bea898338b9e5b4
- https://git.kernel.org/stable/c/aa0c07c1f20e05b30019bff083ec43665536f06f
- https://git.kernel.org/stable/c/dc941fec0719d0471a5902424d6b2a17df233193
- https://git.kernel.org/stable/c/fb7a0d334894206ae35f023a82cad5a290fd7386
- https://git.kernel.org/stable/c/39ca83ed73db9edcc6d70c0dc7a73085a4725012
- https://git.kernel.org/stable/c/592f69b41766d366dbb8ff4ef5a67c4396527bbe
- https://git.kernel.org/stable/c/99951b62bf20cec9247f633a3bea898338b9e5b4
- https://git.kernel.org/stable/c/aa0c07c1f20e05b30019bff083ec43665536f06f
- https://git.kernel.org/stable/c/dc941fec0719d0471a5902424d6b2a17df233193
- https://git.kernel.org/stable/c/fb7a0d334894206ae35f023a82cad5a290fd7386
- https://lists.debian.org/debian-lts-announce/2024/06/msg00019.html
Raw JSON (NVD)
Show
{
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"integrityImpact": "NONE",
"userInteraction": "NONE",
"attackComplexity": "LOW",
"availabilityImpact": "HIGH",
"privilegesRequired": "LOW",
"confidentialityImpact": "NONE"
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"descriptions": [
{
"lang": "en",
"value": "In the Linux kernel, the following vulnerability has been resolved:\n\nmptcp: ensure snd_nxt is properly initialized on connect\n\nChristoph reported a splat hinting at a corrupted snd_una:\n\n WARNING: CPU: 1 PID: 38 at net/mptcp/protocol.c:1005 __mptcp_clean_una+0x4b3/0x620 net/mptcp/protocol.c:1005\n Modules linked in:\n CPU: 1 PID: 38 Comm: kworker/1:1 Not tainted 6.9.0-rc1-gbbeac67456c9 #59\n Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.11.0-2.el7 04/01/2014\n Workqueue: events mptcp_worker\n RIP: 0010:__mptcp_clean_una+0x4b3/0x620 net/mptcp/protocol.c:1005\n Code: be 06 01 00 00 bf 06 01 00 00 e8 a8 12 e7 fe e9 00 fe ff ff e8\n \t8e 1a e7 fe 0f b7 ab 3e 02 00 00 e9 d3 fd ff ff e8 7d 1a e7 fe\n \t<0f> 0b 4c 8b bb e0 05 00 00 e9 74 fc ff ff e8 6a 1a e7 fe 0f 0b e9\n RSP: 0018:ffffc9000013fd48 EFLAGS: 00010293\n RAX: 0000000000000000 RBX: ffff8881029bd280 RCX: ffffffff82382fe4\n RDX: ffff8881003cbd00 RSI: ffffffff823833c3 RDI: 0000000000000001\n RBP: 0000000000000000 R08: 0000000000000001 R09: 0000000000000000\n R10: 0000000000000000 R11: fefefefefefefeff R12: ffff888138ba8000\n R13: 0000000000000106 R14: ffff8881029bd908 R15: ffff888126560000\n FS: 0000000000000000(0000) GS:ffff88813bd00000(0000) knlGS:0000000000000000\n CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033\n CR2: 00007f604a5dae38 CR3: 0000000101dac002 CR4: 0000000000170ef0\n Call Trace:\n <TASK>\n __mptcp_clean_una_wakeup net/mptcp/protocol.c:1055 [inline]\n mptcp_clean_una_wakeup net/mptcp/protocol.c:1062 [inline]\n __mptcp_retrans+0x7f/0x7e0 net/mptcp/protocol.c:2615\n mptcp_worker+0x434/0x740 net/mptcp/protocol.c:2767\n process_one_work+0x1e0/0x560 kernel/workqueue.c:3254\n process_scheduled_works kernel/workqueue.c:3335 [inline]\n worker_thread+0x3c7/0x640 kernel/workqueue.c:3416\n kthread+0x121/0x170 kernel/kthread.c:388\n ret_from_fork+0x44/0x50 arch/x86/kernel/process.c:147\n ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:243\n </TASK>\n\nWhen fallback to TCP happens early on a client socket, snd_nxt\nis not yet initialized and any incoming ack will copy such value\ninto snd_una. If the mptcp worker (dumbly) tries mptcp-level\nre-injection after such ack, that would unconditionally trigger a send\nbuffer cleanup using 'bad' snd_una values.\n\nWe could easily disable re-injection for fallback sockets, but such\ndumb behavior already helped catching a few subtle issues and a very\nlow to zero impact in practice.\n\nInstead address the issue always initializing snd_nxt (and write_seq,\nfor consistency) at connect time."
},
{
"lang": "es",
"value": "En el kernel de Linux, se resolvió la siguiente vulnerabilidad: mptcp: asegúrese de que snd_nxt se inicialice correctamente al conectar Christoph informó un símbolo que indica un snd_una dañado: ADVERTENCIA: CPU: 1 PID: 38 en net/mptcp/protocol.c:1005 __mptcp_clean_una +0x4b3/0x620 net/mptcp/protocol.c:1005 Módulos vinculados en: CPU: 1 PID: 38 Comm: kworker/1:1 No contaminado 6.9.0-rc1-gbbeac67456c9 #59 Nombre del hardware: PC estándar QEMU (i440FX + PIIX, 1996), BIOS 1.11.0-2.el7 01/04/2014 Cola de trabajo: eventos mptcp_worker RIP: 0010:__mptcp_clean_una+0x4b3/0x620 net/mptcp/protocol.c:1005 Código: be 06 01 00 00 bf 06 01 00 00 e8 a8 12 e7 fe e9 00 fe ff ff e8 8e 1a e7 fe 0f b7 ab 3e 02 00 00 e9 d3 fd ff ff e8 7d 1a e7 fe <0f> 0b 4c 8b bb e0 05 00 00 e9 74 fc ff ff e8 6a 1a e7 fe 0f 0b e9 RSP: 0018:ffffc9000013fd48 EFLAGS: 00010293 RAX: 0000000000000000 RBX: ffff8881029bd280 RCX: ffffffff82382fe4 RDX: 3cbd00 RSI: ffffffff823833c3 RDI: 0000000000000001 RBP: 0000000000000000 R08: 0000000000000001 R09: 0000000000000000 R10: 00000000000000000 R11: fefefefefefefeff R12 : ffff888138ba8000 R13: 0000000000000106 R14: ffff8881029bd908 R15: ffff888126560000 FS: 00000000000000000(0000) GS:ffff88813bd00000(0000) nlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007f604a5dae38 CR3: 0000000101dac002 CR4: 0000000000170ef0 Rastreo de llamadas: __mptcp_clean_una_wakeup net/mptcp/protocol.c:1055 [en línea] mptcp_clean_una_wakeup net/mptcp/protocol.c:1062 [en línea] __mptcp_retrans+0x7f/0x7e0 net/mptcp/protocol.c:2615 mptcp_worker+0x434/ 0x740 neto/ mptcp/protocol.c:2767 Process_one_work+0x1e0/0x560 kernel/workqueue.c:3254 Process_scheduled_works kernel/workqueue.c:3335 [en línea] work_thread+0x3c7/0x640 kernel/workqueue.c:3416 kthread+0x121/0x170 kernel/kthread .c:388 ret_from_fork+0x44/0x50 arch/x86/kernel/process.c:147 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:243 Cuando el retorno a TCP ocurre temprano en un socket de cliente , snd_nxt aún no está inicializado y cualquier confirmación entrante copiará dicho valor en snd_una. Si el trabajador mptcp (tontamente) intenta la reinyección a nivel de mptcp después de tal confirmación, eso desencadenaría incondicionalmente una sanitización del búfer de envío utilizando valores snd_una 'incorrectos'. Podríamos desactivar fácilmente la reinyección para los sockets de respaldo, pero un comportamiento tan tonto ya ayudó a detectar algunos problemas sutiles y un impacto de muy bajo a cero en la práctica. En su lugar, resuelva el problema siempre inicializando snd_nxt (y write_seq, para mantener la coherencia) en el momento de la conexión."
}
],
"lastModified": "2026-06-17T07:37:16.990",
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