Skip to content
Fencer Vulns
high 8.8

CVE-2023-43635 json

Vault Key Sealed With SHA1 PCRs

published 2023-09-20 3 y ago modified 2026-06-17 4 mo ago also GHSA-4jvr-vj2c-8q37 , GO-2026-4434 , EUVD-2023-48035

cvss
8.8
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.1%
EPSS 0.1% chance of exploitation in 30 days, percentile 1%
public exploits
0
none known

Summary

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.

Patch / fix

  • go github.com/lf-edge/eve 0.0.0-20230519072751-977f42b07fa9
  • LF-Edge, Zededa EVE OS 9.5.0
  • linuxfoundation edge_virtualization_engine 9.5.0
  • govulncheck-vulndb openSUSE Leap 15.6 0.0.20260226T182644-150000.1.149.1

suse advisories SUSE-SU-2026:0757-1

  • govulncheck-vulndb openSUSE Leap 16.0 0.0.20260723T184607-160000.1.1

opensuse advisories openSUSE-SU-2026:21483-1

CISA SSVC

Exploitation
none
Automatable
no
Technical impact
total
Assessed
2 y ago

Exploit prediction

0.12% chance of exploitation in the next 30 days, higher than 1% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 3.1 8.8 CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H
NVD 3.1 8.8 CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H
GitHub 3.1 6.7 CVSS:3.1/AV:P/AC:H/PR:L/UI:N/S:C/C:H/I:H/A:N

Affected packages

ecosystem package affected fixed in
go github.com/lf-edge/eve
<0.0.0-20230519072751-977f42b07fa9
0.0.0-20230519072751-977f42b07fa9

Affected products

  • LF-Edge, Zededa EVE OS
  • linuxfoundation edge_virtualization_engine

Classification

Weakness
  • CWE-522 Insufficiently Protected Credentials
  • CWE-328 Use of Weak Hash
  • CWE-327 Use of a Broken or Risky Cryptographic Algorithm

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.