In the Linux kernel, the following vulnerability has been resolved:
video: screen_info: Relocate framebuffers behind PCI bridges
Apply PCI host-bridge window offsets to screen_info framebuffers. Fixes
invalid access to I/O memory.
Resources behind a PCI host bridge can be relocated by a certain offset
in the kernel's CPU address range used for I/O. The framebuffer memory
range stored in screen_info refers to the CPU addresses as seen during
boot (where the offset is 0). During boot up, firmware may assign a
different memory offset to the PCI host bridge and thereby relocating
the framebuffer address of the PCI graphics device as seen by the kernel.
The information in screen_info must be updated as well.
The helper pcibios_bus_to_resource() performs the relocation of the
screen_info's framebuffer resource (given in PCI bus addresses). The
result matches the I/O-memory resource of the PCI graphics device (given
in CPU addresses). As before, we store away the information necessary to
later update the information in screen_info itself.
Commit 78aa89d1dfba ("firmware/sysfb: Update screen_info for relocated
EFI framebuffers") added the code for updating screen_info. It is based
on similar functionality that pre-existed in efifb. Efifb uses a pointer
to the PCI resource, while the newer code does a memcpy of the region.
Hence efifb sees any updates to the PCI resource and avoids the issue.
v3:
- Only use struct pci_bus_region for PCI bus addresses (Bjorn)
- Clarify address semantics in commit messages and comments (Bjorn)
v2:
- Fixed tags (Takashi, Ivan)
- Updated information on efifb
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. 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