Security readout for executives and security teams
Plain-English summary
CVE-2020-27749 is a GRUB2 bootloader flaw where oversized variable expansion can overflow a small stack buffer. Successful exploitation could let an attacker alter bootloader execution and potentially bypass Secure Boot, threatening confidentiality, integrity, and availability before the operating system fully starts.
Executive priority
Prioritize remediation for internet-facing operations platforms, regulated workloads, laptops, and servers relying on Secure Boot. Treat this as a boot-chain integrity risk, even without confirmed active exploitation in the provided sources.
Technical view
GRUB2 versions described as prior to 2.06 expand command-line variable names into a 1 KB stack buffer without sufficient bounds checking. A sufficiently large variable payload can cause a stack-based buffer overflow, corrupt the stack frame, and allow execution control, with possible Secure Boot circumvention.
Likely exposure
Exposure is most likely on systems or appliances using affected GRUB2 bootloader builds, especially Linux distributions or vendor products covered by Fedora, Gentoo, Red Hat, or NetApp references. Exact affected package versions and platform scope must be confirmed from vendor advisories.
Exploitation context
The supplied sources do not establish active exploitation, and the CVE is not marked KEV. The issue is serious because it affects boot trust boundaries, but practical attack prerequisites are not fully described in the provided bundle.
Researcher notes
The core weakness is CWE-121 stack-based buffer overflow in GRUB2 variable expansion. The bundle lacks CVSS, detailed prerequisites, and exploit maturity evidence, so validation should stay package- and vendor-advisory focused.
Mitigation direction
- Apply GRUB2 updates from the relevant operating system or appliance vendor.
- Follow vendor Secure Boot and bootloader update guidance exactly.
- Review Fedora, Gentoo, Red Hat, and NetApp advisories for product-specific fixes.
- Check vendor guidance if no patch path is available for a platform.
Validation and detection
- Inventory systems and appliances using GRUB2 bootloader packages.
- Compare installed GRUB2 versions against vendor advisory affected ranges.
- Verify updated bootloader packages and boot artifacts are installed.
- Confirm Secure Boot-related vendor update steps were completed where applicable.
Public sources used
Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.
Conservative CVE-to-ATT&CK context
These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.
ATT&CK lookup starting points
Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.
CWE-121: Exact CWE lookup
Use the exact CWE identifier as the starting point before reviewing related ATT&CK behavior. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.
Open ATT&CK lookupCVE-2020-27749 mapping review
Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.
Open ATT&CK lookup- Severity
- Unknown
- CVSS
- Not scored
- Known Exploited
- No
- Published
CNA and ADP enrichment extracted from CVE v5
These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.
CVSS and timeline data
No CVSS vectors or timeline events were available in the normalized CVE source material.
Source materials
- CVE List V5 sourceCVE List V5
- https://bugzilla.redhat.com/show_bug.cgi?id=1899966CVE reference · x_refsource_MISC
- FEDORA-2021-cab258a413CVE reference · vendor-advisory, x_refsource_FEDORA
- GLSA-202104-05CVE reference · vendor-advisory, x_refsource_GENTOO
- https://security.netapp.com/advisory/ntap-20220325-0001/CVE reference · x_refsource_CONFIRM
Products and packages named in the record
CWE details
CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.
Stack-based Buffer Overflow
Stack-based Buffer Overflow represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.