{"id":"CVE-2025-39900","state":"PUBLISHED","title":"net_sched: gen_estimator: fix est_timer() vs CONFIG_PREEMPT_RT=y","description":"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>","publishedAt":"2025-10-01T07:42:47.785Z","updatedAt":"2026-05-11T21:38:34.749Z","severity":{"score":5.5,"label":"Medium","version":"3.1","vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H","source":"CISA-ADP"},"assigner":"Linux","products":["Linux Linux"],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"d2d6422f8bd17c6bb205133e290625a564194496","status":"affected","lessThan":"a22ec2ee824be30803068a52f78f7ffe3bc879fb","versionType":"git"},{"version":"d2d6422f8bd17c6bb205133e290625a564194496","status":"affected","lessThan":"e79923824c48b930609680be04cb29253fc4a17d","versionType":"git"},{"version":"d2d6422f8bd17c6bb205133e290625a564194496","status":"affected","lessThan":"9f74c0ea9b26d1505d55b61e36b1623dd347e1d1","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/core/gen_estimator.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"6.12","status":"affected"},{"version":"0","status":"unaffected","lessThan":"6.12","versionType":"semver"},{"version":"6.12.46","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.16.6","status":"unaffected","lessThanOrEqual":"6.16.*","versionType":"semver"},{"version":"6.17","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/core/gen_estimator.c"]}],"references":["https://git.kernel.org/stable/c/a22ec2ee824be30803068a52f78f7ffe3bc879fb","https://git.kernel.org/stable/c/e79923824c48b930609680be04cb29253fc4a17d","https://git.kernel.org/stable/c/9f74c0ea9b26d1505d55b61e36b1623dd347e1d1"],"weaknesses":[],"ingestedAt":"2026-10-29T20:09:09.358Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2025/39xxx/CVE-2025-39900.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2025-39900","state":"PUBLISHED","datePublished":"2025-10-01T07:42:47.785Z","dateUpdated":"2026-05-11T21:38:34.749Z","assignerShortName":"Linux","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateReserved":"2025-04-16T07:20:57.146Z"},"containers":{"cna":{"title":"net_sched: gen_estimator: fix est_timer() vs CONFIG_PREEMPT_RT=y","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>"}],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"d2d6422f8bd17c6bb205133e290625a564194496","status":"affected","lessThan":"a22ec2ee824be30803068a52f78f7ffe3bc879fb","versionType":"git"},{"version":"d2d6422f8bd17c6bb205133e290625a564194496","status":"affected","lessThan":"e79923824c48b930609680be04cb29253fc4a17d","versionType":"git"},{"version":"d2d6422f8bd17c6bb205133e290625a564194496","status":"affected","lessThan":"9f74c0ea9b26d1505d55b61e36b1623dd347e1d1","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/core/gen_estimator.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"6.12","status":"affected"},{"version":"0","status":"unaffected","lessThan":"6.12","versionType":"semver"},{"version":"6.12.46","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.16.6","status":"unaffected","lessThanOrEqual":"6.16.*","versionType":"semver"},{"version":"6.17","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/core/gen_estimator.c"]}],"references":[{"url":"https://git.kernel.org/stable/c/a22ec2ee824be30803068a52f78f7ffe3bc879fb"},{"url":"https://git.kernel.org/stable/c/e79923824c48b930609680be04cb29253fc4a17d"},{"url":"https://git.kernel.org/stable/c/9f74c0ea9b26d1505d55b61e36b1623dd347e1d1"}],"providerMetadata":{"shortName":"Linux","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateUpdated":"2026-05-11T21:38:34.749Z"},"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.12","versionEndExcluding":"6.12.46"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.12","versionEndExcluding":"6.16.6"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.12","versionEndExcluding":"6.17"}]}]}],"x_generator":{"engine":"bippy-1.2.0"}},"adp":[{"title":"CISA ADP Vulnrichment","metrics":[{"cvssV3_1":{"scope":"UNCHANGED","version":"3.1","baseScore":5.5,"attackVector":"LOCAL","baseSeverity":"MEDIUM","vectorString":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H","integrityImpact":"NONE","userInteraction":"NONE","attackComplexity":"LOW","availabilityImpact":"HIGH","privilegesRequired":"LOW","confidentialityImpact":"NONE"}},{"other":{"type":"ssvc","content":{"id":"CVE-2025-39900","role":"CISA Coordinator","options":[{"Exploitation":"none"},{"Automatable":"no"},{"Technical Impact":"partial"}],"version":"2.0.3","timestamp":"2026-01-14T19:29:22.173838Z"}}}],"problemTypes":[{"descriptions":[{"lang":"en","type":"CWE","description":"CWE-noinfo Not enough information"}]}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2026-01-14T19:33:14.273Z"}}]}}}