In the Linux kernel, the following vulnerability has been resolved:
um: ubd: Do not use drvdata in release
The drvdata is not available in release. Let's just use container_of()
to get the ubd instance. Otherwise, removing a ubd device will result
in a crash:
RIP: 0033:blk_mq_free_tag_set+0x1f/0xba
RSP: 00000000e2083bf0 EFLAGS: 00010246
RAX: 000000006021463a RBX: 0000000000000348 RCX: 0000000062604d00
RDX: 0000000004208060 RSI: 00000000605241a0 RDI: 0000000000000348
RBP: 00000000e2083c10 R08: 0000000062414010 R09: 00000000601603f7
R10: 000000000000133a R11: 000000006038c4bd R12: 0000000000000000
R13: 0000000060213a5c R14: 0000000062405d20 R15: 00000000604f7aa0
Kernel panic - not syncing: Segfault with no mm
CPU: 0 PID: 17 Comm: kworker/0:1 Not tainted 6.8.0-rc3-00107-gba3f67c11638 #1
Workqueue: events mc_work_proc
Stack:
00000000 604f7ef0 62c5d000 62405d20
e2083c30 6002c776 6002c755 600e47ff
e2083c60 6025ffe3 04208060 603d36e0
Call Trace:
[<6002c776>] ubd_device_release+0x21/0x55
[<6002c755>] ? ubd_device_release+0x0/0x55
[<600e47ff>] ? kfree+0x0/0x100
[<6025ffe3>] device_release+0x70/0xba
[<60381d6a>] kobject_put+0xb5/0xe2
[<6026027b>] put_device+0x19/0x1c
[<6026a036>] platform_device_put+0x26/0x29
[<6026ac5a>] platform_device_unregister+0x2c/0x2e
[<6002c52e>] ubd_remove+0xb8/0xd6
[<6002bb74>] ? mconsole_reply+0x0/0x50
[<6002b926>] mconsole_remove+0x160/0x1cc
[<6002bbbc>] ? mconsole_reply+0x48/0x50
[<6003379c>] ? um_set_signals+0x3b/0x43
[<60061c55>] ? update_min_vruntime+0x14/0x70
[<6006251f>] ? dequeue_task_fair+0x164/0x235
[<600620aa>] ? update_cfs_group+0x0/0x40
[<603a0e77>] ? __schedule+0x0/0x3ed
[<60033761>] ? um_set_signals+0x0/0x43
[<6002af6a>] mc_work_proc+0x77/0x91
[<600520b4>] process_scheduled_works+0x1af/0x2c3
[<6004ede3>] ? assign_work+0x0/0x58
[<600527a1>] worker_thread+0x2f7/0x37a
[<6004ee3b>] ? set_pf_worker+0x0/0x64
[<6005765d>] ? arch_local_irq_save+0x0/0x2d
[<60058e07>] ? kthread_exit+0x0/0x3a
[<600524aa>] ? worker_thread+0x0/0x37a
[<60058f9f>] kthread+0x130/0x135
[<6002068e>] new_thread_handler+0x85/0xb6
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
- 0.2% within 30 daysSource: FIRST EPSS (model v2026.06.15, score date 2026-11-07). 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