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CVE-2025-39900

Estado: ModificadaMedia (5.5)—

In the Linux kernel, the following vulnerability has been resolved:

net_sched: gen_estimator: fix est_timer() vs CONFIG_PREEMPT_RT=y

syzbot reported a WARNING in est_timer() [1]

Problem here is that with CONFIG_PREEMPT_RT=y, timer callbacks can be preempted.

Adopt preempt_disable_nested()/preempt_enable_nested() to fix this.

Detalles técnicos trazas, registros y código del informe original
[1]
 WARNING: CPU: 0 PID: 16 at ./include/linux/seqlock.h:221 __seqprop_assert include/linux/seqlock.h:221 [inline]
 WARNING: CPU: 0 PID: 16 at ./include/linux/seqlock.h:221 est_timer+0x6dc/0x9f0 net/core/gen_estimator.c:93
Modules linked in:
CPU: 0 UID: 0 PID: 16 Comm: ktimers/0 Not tainted syzkaller #0 PREEMPT_{RT,(full)}
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025
 RIP: 0010:__seqprop_assert include/linux/seqlock.h:221 [inline]
 RIP: 0010:est_timer+0x6dc/0x9f0 net/core/gen_estimator.c:93
Call Trace:
 <TASK>
  call_timer_fn+0x17e/0x5f0 kernel/time/timer.c:1747
  expire_timers kernel/time/timer.c:1798 [inline]
  __run_timers kernel/time/timer.c:2372 [inline]
  __run_timer_base+0x648/0x970 kernel/time/timer.c:2384
  run_timer_base kernel/time/timer.c:2393 [inline]
  run_timer_softirq+0xb7/0x180 kernel/time/timer.c:2403
  handle_softirqs+0x22c/0x710 kernel/softirq.c:579
  __do_softirq kernel/softirq.c:613 [inline]
  run_ktimerd+0xcf/0x190 kernel/softirq.c:1043
  smpboot_thread_fn+0x53f/0xa60 kernel/smpboot.c:160
  kthread+0x70e/0x8a0 kernel/kthread.c:463
  ret_from_fork+0x3fc/0x770 arch/x86/kernel/process.c:148
  ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>

CVSS

Probabilidad de explotación (EPSS)

EPSS (Exploit Prediction Scoring System, de FIRST) estima la probabilidad de que una vulnerabilidad sea explotada en 30 días. Complementa a CVSS (impacto) y a CISA KEV (explotación confirmada).

Tecnologías afectadas (1)

Linux — Linux Kernel

CWE

Referencias

JSON original (NVD)

Mostrar
{
  "id": "CVE-2025-39900",
  "cveTags": [],
  "metrics": {
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        "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
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          "role": "CISA Coordinator",
          "options": [
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              "exploitation": "none"
            },
            {
              "automatable": "no"
            },
            {
              "technicalImpact": "partial"
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          "version": "2.0.3",
          "timestamp": "2026-01-14T19:29:22.173838Z"
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          "integrityImpact": "NONE",
          "userInteraction": "NONE",
          "attackComplexity": "LOW",
          "availabilityImpact": "HIGH",
          "privilegesRequired": "LOW",
          "confidentialityImpact": "NONE"
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        "exploitabilityScore": 1.8
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  ],
  "published": "2025-10-01T08:15:32.740",
  "references": [
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    }
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  "descriptions": [
    {
      "lang": "en",
      "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet_sched: gen_estimator: fix est_timer() vs CONFIG_PREEMPT_RT=y\n\nsyzbot reported a WARNING in est_timer() [1]\n\nProblem here is that with CONFIG_PREEMPT_RT=y, timer callbacks\ncan be preempted.\n\nAdopt preempt_disable_nested()/preempt_enable_nested() to fix this.\n\n[1]\n WARNING: CPU: 0 PID: 16 at ./include/linux/seqlock.h:221 __seqprop_assert include/linux/seqlock.h:221 [inline]\n WARNING: CPU: 0 PID: 16 at ./include/linux/seqlock.h:221 est_timer+0x6dc/0x9f0 net/core/gen_estimator.c:93\nModules linked in:\nCPU: 0 UID: 0 PID: 16 Comm: ktimers/0 Not tainted syzkaller #0 PREEMPT_{RT,(full)}\nHardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025\n RIP: 0010:__seqprop_assert include/linux/seqlock.h:221 [inline]\n RIP: 0010:est_timer+0x6dc/0x9f0 net/core/gen_estimator.c:93\nCall Trace:\n <TASK>\n  call_timer_fn+0x17e/0x5f0 kernel/time/timer.c:1747\n  expire_timers kernel/time/timer.c:1798 [inline]\n  __run_timers kernel/time/timer.c:2372 [inline]\n  __run_timer_base+0x648/0x970 kernel/time/timer.c:2384\n  run_timer_base kernel/time/timer.c:2393 [inline]\n  run_timer_softirq+0xb7/0x180 kernel/time/timer.c:2403\n  handle_softirqs+0x22c/0x710 kernel/softirq.c:579\n  __do_softirq kernel/softirq.c:613 [inline]\n  run_ktimerd+0xcf/0x190 kernel/softirq.c:1043\n  smpboot_thread_fn+0x53f/0xa60 kernel/smpboot.c:160\n  kthread+0x70e/0x8a0 kernel/kthread.c:463\n  ret_from_fork+0x3fc/0x770 arch/x86/kernel/process.c:148\n  ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245\n </TASK>"
    }
  ],
  "lastModified": "2026-06-17T09:18:46.970",
  "configurations": [
    {
      "nodes": [
        {
          "negate": false,
          "cpeMatch": [
            {
              "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
              "vulnerable": true,
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}