In the Linux kernel, the following vulnerability has been resolved:
PCI/bwctrl: Fix NULL pointer dereference on bus number exhaustion
When BIOS neglects to assign bus numbers to PCI bridges, the kernel
attempts to correct that during PCI device enumeration. If it runs out
of bus numbers, no pci_bus is allocated and the "subordinate" pointer in
the bridge's pci_dev remains NULL.
The PCIe bandwidth controller erroneously does not check for a NULL
subordinate pointer and dereferences it on probe.
Bandwidth control of unusable devices below the bridge is of questionable
utility, so simply error out instead. This mirrors what PCIe hotplug does
since commit 62e4492c3063 ("PCI: Prevent NULL dereference during pciehp
probe").
The PCI core emits a message with KERN_INFO severity if it has run out of
bus numbers. PCIe hotplug emits an additional message with KERN_ERR
severity to inform the user that hotplug functionality is disabled at the
bridge. A similar message for bandwidth control does not seem merited,
given that its only purpose so far is to expose an up-to-date link speed
in sysfs and throttle the link speed on certain laptops with limited
Thermal Design Power. So error out silently.
User-visible messages:
pci 0000:16:02.0: bridge configuration invalid ([bus 00-00]), reconfiguring
[...]
pci_bus 0000:45: busn_res: [bus 45-74] end is updated to 74
pci 0000:16:02.0: devices behind bridge are unusable because [bus 45-74] cannot be assigned for them
[...]
pcieport 0000:16:02.0: pciehp: Hotplug bridge without secondary bus, ignoring
[...]
BUG: kernel NULL pointer dereference
RIP: pcie_update_link_speed
pcie_bwnotif_enable
pcie_bwnotif_probe
pcie_port_probe_service
really_probe
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
- 0.3% within 30 daysSource: FIRST EPSS (model v2026.06.15, score date 2026-10-25). 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