Improper input validation in Siemens Efibootguard
CVE-2023-39950
efibootguard is a simple UEFI boot loader with support for safely switching between current and updated partition sets. Insufficient or missing validation and sanitization of input from untrustworthy bootloader environment files can cause crashes and probably also code injections into `bg_setenv`) or programs using `libebgenv`. This is triggered when the affected components try to modify a manipulated environment, in particular its user variables. Furthermore, `bg_printenv` may crash over invalid read accesses or report invalid results. Not affected by this issue is EFI Boot Guard's bootloader EFI binary. EFI Boot Guard release v0.15 contains required patches to sanitize and validate the bootloader environment prior to processing it in userspace. Its library and tools should be updated, so should programs statically linked against it. An update of the bootloader EFI executable is not required. The only way to prevent the issue with an unpatched EFI Boot Guard version is to avoid accesses to user variables, specifically modifications to them.
Vulnerability class: Drupalgeddon 2 (CVE-2018-7600)
Published · last modified .
CVSS v3 metric
CVSS v3 base score 6.1 (Medium). Vector: CVSS:3.1/AV:P/AC:L/PR:N/UI:N/S:C/C:N/I:H/A:L.
EPSS exploit prediction
EPSS: 0.004 (34.5th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 35th percentile — 34.5% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.004 · newest: 0.004 · change: 0.000
Affected products
- Siemens Efibootguard — versions < 0.15
Weakness classification (CWE)
References
- github.com/siemens/efibootguard/security/advisories/GHSA-j6pp-7g99-24m7 (Third Party Advisory)
- github.com/siemens/efibootguard/blob/master/docs/API.md (Third Party Advisory)
- github.com/siemens/efibootguard/blob/master/docs/TOOLS.md (Third Party Advisory)
- github.com/siemens/efibootguard/blob/master/docs/TOOLS.md (Third Party Advisory)
- github.com/siemens/efibootguard/tags (Third Party Advisory)
Frequently asked questions
- What is CVE-2023-39950?
- CVE-2023-39950 is a medium-severity vulnerability in Siemens Efibootguard, classified under Improper Input Validation. CVSS score: 6.1/10. Published 2023-08-14.
- How severe is CVE-2023-39950?
- Medium severity. CVSS v3 base score is 6.1 out of 10.