In the Linux kernel, the following vulnerability has been resolved:
riscv: fgraph: Fix stack layout to match __arch_ftrace_regs argument of ftrace_return_to_handler
Naresh Kamboju reported a "Bad frame pointer" kernel warning while
running LTP trace ftrace_stress_test.sh in riscv. We can reproduce the
same issue with the following command:
$ cd /sys/kernel/debug/tracing
$ echo 'f:myprobe do_nanosleep%return args1=$retval' > dynamic_events
$ echo 1 > events/fprobes/enable
$ echo 1 > tracing_on
$ sleep 1
And we can get the following kernel warning:
[ 127.692888] ------------[ cut here ]------------
[ 127.693755] Bad frame pointer: expected ff2000000065be50, received ba34c141e9594000
[ 127.693755] from func do_nanosleep return to ffffffff800ccb16
[ 127.698699] WARNING: CPU: 1 PID: 129 at kernel/trace/fgraph.c:755 ftrace_return_to_handler+0x1b2/0x1be
[ 127.699894] Modules linked in:
[ 127.700908] CPU: 1 UID: 0 PID: 129 Comm: sleep Not tainted 6.14.0-rc3-g0ab191c74642 #32
[ 127.701453] Hardware name: riscv-virtio,qemu (DT)
[ 127.701859] epc : ftrace_return_to_handler+0x1b2/0x1be
[ 127.702032] ra : ftrace_return_to_handler+0x1b2/0x1be
[ 127.702151] epc : ffffffff8013b5e0 ra : ffffffff8013b5e0 sp : ff2000000065bd10
[ 127.702221] gp : ffffffff819c12f8 tp : ff60000080853100 t0 : 6e00000000000000
[ 127.702284] t1 : 0000000000000020 t2 : 6e7566206d6f7266 s0 : ff2000000065bd80
[ 127.702346] s1 : ff60000081262000 a0 : 000000000000007b a1 : ffffffff81894f20
[ 127.702408] a2 : 0000000000000010 a3 : fffffffffffffffe a4 : 0000000000000000
[ 127.702470] a5 : 0000000000000000 a6 : 0000000000000008 a7 : 0000000000000038
[ 127.702530] s2 : ba34c141e9594000 s3 : 0000000000000000 s4 : ff2000000065bdd0
[ 127.702591] s5 : 00007fff8adcf400 s6 : 000055556dc1d8c0 s7 : 0000000000000068
[ 127.702651] s8 : 00007fff8adf5d10 s9 : 000000000000006d s10: 0000000000000001
[ 127.702710] s11: 00005555737377c8 t3 : ffffffff819d899e t4 : ffffffff819d899e
[ 127.702769] t5 : ffffffff819d89a0 t6 : ff2000000065bb18
[ 127.702826] status: 0000000200000120 badaddr: 0000000000000000 cause: 0000000000000003
[ 127.703292] [] ftrace_return_to_handler+0x1b2/0x1be
[ 127.703760] [] return_to_handler+0x16/0x26
[ 127.704009] [] return_to_handler+0x0/0x26
[ 127.704057] [] common_nsleep+0x42/0x54
[ 127.704117] [] __riscv_sys_clock_nanosleep+0xba/0x10a
[ 127.704176] [] do_trap_ecall_u+0x188/0x218
[ 127.704295] [] handle_exception+0x14a/0x156
[ 127.705436] ---[ end trace 0000000000000000 ]---
The reason is that the stack layout for constructing argument for the
ftrace_return_to_handler in the return_to_handler does not match the
__arch_ftrace_regs structure of riscv, leading to unexpected results.
What the EG score is made of (scorer v4.0: the three questions the 0–10 score mixes, published apart · methodology)
The EG score (7.8): severity, escalated by confirmed exploitation. This CVE's 7.8 is its impact severity (EG Severity), not escalated.
- EG Severity
- 7.8 HIGHCVSS-B, impact only: no KEV listing, EPSS or EG-KEV tier raises it.GitHub Security Advisory CVSS
- EG Likelihood
- 0.2% within 30 daysSource: FIRST EPSS (model v2026.06.15, score date 2026-10-27). 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 low or medium mission impact; Track* at high (mission-essential systems).CISA BOD 26-04: 14 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 low or medium mission impact; Track* at high (mission-essential systems).
A fix is available. Apply it within your standard update timelines.
Exploitation none (no CISA value, KEV listing or exploit code on record) · Automatable no (CISA's BOD 26-04 default) · Technical impact total (CISA's BOD 26-04 default). EchelonGraph holds no SSVC assessment of this CVE from CISA: none of these inputs is from 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)14 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's BOD 26-04 default) · Technical impact total (CISA's BOD 26-04 default). Where an input reads “CISA's BOD 26-04 default”, no one has published it for this CVE, and CISA's implementation guidance says: “If “Automatable” and “Technical Impact” information items about a CVE ID are not available and the CVE ID is not in the KEV Catalog, CISA will treat its values as “no” and “total,” respectively, until CISA or a third party provides metadata about the CVE ID. CISA will always provide the Vulnrichment data for a CVE ID listed in the KEV Catalog.” 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