Enterprise LinuxOperating system · Redhat
CVE-2020-14311
Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.
NVD · uneditedThere is an issue with grub2 before version 2.06 while handling symlink on ext filesystems. A filesystem containing a symbolic link with an inode size of UINT32_MAX causes an arithmetic overflow leading to a zero-sized memory allocation with subsequent heap-based buffer overflow.
Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.
dbcve analysis · high confidencegrub2 before version 2.06 contains a heap-based buffer overflow vulnerability when handling symbolic links on ext filesystems. When a symlink has an inode size of UINT32_MAX, an arithmetic overflow occurs during size calculation, resulting in a zero-sized memory allocation followed by heap overflow.
Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.
Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.
NVD · CPE data
Enterprise LinuxOperating system
= 7.0= 8.0
Enterprise Linux EusOperating system
= 8.1= 8.2
Enterprise Linux Server AusOperating system
= 8.2
Enterprise Linux Server TusOperating system
= 8.2
Ubuntu LinuxOperating system
= 14.04= 16.04= 18.04= 20.04< 2.06= 15.1= 15.2CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.
From the vector- Attack vector
- Local
- Complexity
- Low
- Privileges
- High
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- None
- Integrity
- High
- Availability
- High
CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:H/A:H
Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.
dbcve checksWork through these to decide whether this CVE applies to you.
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Check installed grub2 versionRun 'grub2-install --version' or 'grub-install --version', or check the package manager: 'rpm -q grub2' (RHEL) or 'dpkg -l | grep grub' (Ubuntu) or 'rpm -q grub2' (SUSE)Affected if Version is below 2.06 or version cannot be determined (likely vulnerable)
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Verify ext filesystem support in grubInspect grub configuration: check /boot/grub/grub.cfg or /boot/grub2/grub.cfg for 'ext2' or 'ext4' module loading, or check if /boot/grub/*/ext*.mod existsAffected if Ext filesystem modules are present (vulnerability can be triggered when accessing ext filesystems)
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Confirm grub is used as bootloaderCheck for grub files in /boot: ls -la /boot/grub* or check bootloader configuration: 'efibootmgr -v' (UEFI) or 'bootctl status' (systemd)Affected if Grub is the active bootloader (the vulnerable code runs at boot time)
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Identify host OS and versionRun 'cat /etc/os-release' or 'hostnamectl' to determine if the system runs RHEL 7/8, Ubuntu 14.04/16.04/18.04/20.04, or openSUSE Leap 15.1/15.2Affected if OS matches any affected distribution version listed in the CVE
A system is affected if it uses grub2 as its bootloader with version below 2.06 and has ext filesystem support enabled, which is the default for Linux systems.
Generated from the published advisory. Verify against your own configuration.
Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.
From vendor data2.06
Upgrade grub2 to version 2.06 or later. As grub2 is the bootloader, ensure a recovery mechanism (such as a live CD/USB) is available before applying the update.
Fix this in Enterprise Linux
Scoped from the published advisory
- Consultation3.0 h
- Implementation4.0 h
- Testing3.0 h
- Review / QA2.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $3,408.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2020-14311 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2020-14311 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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- Verified mitigations, workarounds, and config changes
- Version or environment caveats, and links to real fixes
- No weaponised exploit code, or anything meant to cause harm
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