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.
[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:
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
What the EG score is made of (scorer v4.0: the three questions the 0–10 score mixes, published apart · methodology)
The EG score (5.5): severity, escalated by confirmed exploitation. This CVE's 5.5 is its impact severity (EG Severity), not escalated.
- EG Severity
- 5.5 MEDIUMCVSS-B, impact only: no KEV listing, EPSS or EG-KEV tier raises it.GitHub Security Advisory CVSS
- EG Likelihood
- 0.1% within 30 daysSource: FIRST EPSS (model v2026.06.15, score date 2026-10-24). FIRST's exploitation probability, not an EchelonGraph model.
- Confirmed exploitation
- None on record (CISA KEV, EG-KEV Tier 1)Reported apart from the likelihood: an observed fact, not a probability.
- EG Priority
- SSVC Track at medium mission impactTrack at every mission impact level.CISA BOD 26-04: 60 days if the affected system is publicly exposed; Fix on system upgrade if it is not.Each input and its source, and whom BOD 26-04 binds: the SSVC and BOD 26-04 blocks below.
SSVC (CISA's decision table, applied by EchelonGraph)Track at every mission impact level.
A fix is available. Apply it within your standard update timelines.
Exploitation none (CISA Vulnrichment) · Automatable no (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). All three are CISA's SSVC values (Vulnrichment). EchelonGraph applied CISA's decision table to them; CISA publishes SSVC inputs and the table, not a decision for each CVE. Mission impact is CISA's Mission & Well-being decision point, and only you can judge it. CISA's table makes it high when Mission Prevalence is Essential — the vulnerable component "directly provides capabilities that constitute at least one MEF for at least one entity" (MEF: mission essential function) — or when Public Well-Being Impact is Irreversible: "multiple fatalities are likely", the cyber-physical system "is likely lost or destroyed", "extreme or serious externalities" are imposed on other parties, or social systems such as elections or the financial grid "are destabilized and potentially collapse". CISA's decision table
BOD 26-04 (CISA's remediation timeline, Table 1)60 days if the affected system is publicly exposed; Fix on system upgrade if it is not.
The score's inputs: In CISA KEV no (CISA's KEV catalog) · Automatable no (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). Whether your system is publicly exposed is yours to answer. BOD 26-04 binds US Federal Civilian Executive Branch agencies; for anyone else it is CISA's published timeline, a reference rather than an obligation. The directive · how EchelonGraph applies it