Vault Key Sealed With SHA1 PCRs
The measured boot solution implemented in EVE OS leans on a PCR locking mechanism.
Different parts of the system update different PCR values in the TPM, resulting in a unique
value for each PCR entry.
These PCRs are then used in order to seal/unseal a key from the TPM which is used to
encrypt/decrypt the “vault” directory.
This “vault” directory is the most sensitive point in the system and as such, its content should
be protected.
This mechanism is noted in Zededa’s documentation as the “measured boot” mechanism,
designed to protect said “vault”.
The code that’s responsible for generating and fetching the key from the TPM assumes that
SHA256 PCRs are used in order to seal/unseal the key, and as such their presence is being
checked.
The issue here is that the key is not sealed using SHA256 PCRs, but using SHA1 PCRs.
This leads to several issues:
• Machines that have their SHA256 PCRs enabled but SHA1 PCRs disabled, as well
as not sealing their keys at all, meaning the “vault” is not protected from an attacker.
• SHA1 is considered insecure and reduces the complexity level required to unseal the
key in machines which have their SHA1 PCRs enabled.
An attacker can very easily retrieve the contents of the “vault”, which will effectively render
the “measured boot” mechanism meaningless.
What the EG score is made of (scorer v4.0: the three questions the 0–10 score mixes, published apart · methodology)
The EG score (8.8): severity, escalated by confirmed exploitation. This CVE's 8.8 is its impact severity (EG Severity), not escalated.
- EG Severity
- 8.8 HIGHCVSS-B, impact only: no KEV listing, EPSS or EG-KEV tier raises it.NVD CVSS v3 · CVSS v3.0 or v3.1
- EG Likelihood
- 0.1% within 30 daysSource: FIRST EPSS (model v2026.06.15, score date 2026-10-20). 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: 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 (CISA Vulnrichment) · Automatable no (CISA Vulnrichment) · Technical impact total (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)14 days if the affected system is publicly exposed; Fix on system upgrade if it is not.
In CISA KEV no (CISA's KEV catalog) · Automatable no (CISA Vulnrichment) · Technical impact total (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