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Actively exploited in the wild. This CVE is on the CISA Known Exploited Vulnerabilities list — treat remediation as urgent. Federal remediation due by 27 Apr 2022.
FedoraOperating system · Fedoraproject

CVE-2021-3156

HIGH · 7.8 CVSS v3.1 Published 2021-01-26
Fix available
A fix is available. Upgrade to 1.8.32 / 1.9.5 or later.
See remediation →
96/100
Remediation priority · Urgent
In the wild High EPSS Public exploit Zero-click Patch available

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 · unedited
Sudo before 1.9.5p2 contains an off-by-one error that can result in a heap-based buffer overflow, which allows privilege escalation to root via "sudoedit -s" and a command-line argument that ends with a single backslash character.

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 confidence

Heap-based buffer overflow vulnerability in sudo/sudoedit versions prior to 1.9.5p2 caused by an off-by-one error. Local attackers can achieve privilege escalation to root by running 'sudoedit -s' with a command-line argument ending in a single backslash character.

MitigationUpgrade sudo to version 1.9.5p2 or later. As a temporary workaround, avoid using sudoedit -s or implement input validation to reject arguments ending with a backslash.

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
FedoraOperating system
Affected:= 32= 33
Debian LinuxOperating system
Affected:= 9.0= 10.0
SudoApplication
Affected:>= 1.8.2, < 1.8.32>= 1.9.0, < 1.9.5= 1.9.5
Active Iq Unified ManagerApplication
Affected:all versions
Cloud BackupApplication
Affected:all versions
Hci Management NodeApplication
Affected:all versions
Oncommand Unified Manager Core PackageApplication
Affected:all versions
Ontap Select Deploy Administration UtilityApplication
Affected:all versions

CVSS 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
Low
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/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 checks

Work through these to decide whether this CVE applies to you.

  1. Check installed sudo version
    Run 'sudo --version' or 'sudoedit --version' and note the version number displayed
    Affected if The version is 1.8.2 through 1.8.32, or 1.9.0 through 1.9.5, or 1.9.5 (any version in the affected ranges)
  2. Identify sudoedit access for unprivileged users
    Check sudoers configuration with 'sudo -l' for any non-root user, or inspect /etc/sudoers and /etc/sudoers.d/ for sudoedit or sudo permissions granted to non-root users
    Affected if Any unprivileged user has sudoedit or sudo privileges configured in sudoers
  3. Verify sudoedit binary exists and is executable
    Run 'which sudoedit' or 'ls -la /usr/bin/sudoedit' to confirm the sudoedit binary is present
    Affected if The sudoedit binary exists (the vulnerability resides in this binary)
  4. Check if sudoedit can be invoked by non-root users
    As a non-root user, run 'sudoedit -s' with an argument ending in a single backslash character (e.g., 'sudoedit -s test\'), or verify the binary is setuid root with 'ls -la /usr/bin/sudoedit'
    Affected if The sudoedit binary is setuid root or accessible to unprivileged users through sudoers

Your system is affected if sudo version falls within 1.8.2 to 1.8.32, 1.9.0 to 1.9.5, or 1.9.5 AND unprivileged users can access sudoedit via sudoers or the binary is setuid root.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

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.

dbcve · scoped
Upgrade available Upgrade to 1.8.32 / 1.9.5 or later
Fixed in 1.8.321.9.5
Vendor patch www.openwall.com →
Interim mitigation

Upgrade sudo to version 1.9.5p2 or later. As a temporary workaround, avoid using sudoedit -s or implement input validation to reject arguments ending with a backslash.

Recommended fix High confidence

sudo 1.9.5p2 (or later) or sudo 1.8.32 (or later)

  1. Check the current sudo version by running: sudo --version
  2. For Debian/Ubuntu: Run 'sudo apt-get update && sudo apt-get install sudo' to install the latest version with security fixes
  3. For Fedora: Run 'sudo dnf update sudo' to update sudo to a fixed version
  4. For other Linux distributions: Obtain sudo version 1.9.5p2 or later (or 1.8.32 or later) from your distribution's package repository
  5. Verify the fix by running 'sudo --version' and confirming the version is 1.9.5p2 or later, or 1.8.32 or later
  6. For NetApp products listed (Active Iq Unified Manager, Cloud Backup, HCI Management Node, Oncommand Unified Manager, Ontap Select Deploy): Consult the specific NetApp security advisory for applicable patches or mitigations
Caveat Security update; minimal risk as this is a defensive fix. Ensure to test in non-production first as with any system package update.

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Fedora Exploited in the wild — priority engagement
  • Consultation2.0 h
  • Implementation2.0 h
  • Testing2.0 h
  • Review / QA1.0 h
7.0 hours of engineering $1,240
Get it fixed fast

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $1,984.

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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2021-3156 in production — separate from our analysis above.

No notes yet

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • 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
  • No spam, self-promotion, credentials, or personal data