dbcve.org
Debian LinuxOperating system · Debian

CVE-2021-26120

CRITICAL · 9.8 CVSS v3.1 Published 2021-02-22
Fix available
A fix is available. Upgrade to 3.1.39 or later.
See remediation →
100/100
Remediation priority · Urgent
High EPSS Remotely reachable No privileges 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
Smarty before 3.1.39 allows code injection via an unexpected function name after a {function name= substring.

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
How this class of weakness works · CWE-94

The application evaluates attacker-influenced input as code, handing them a way to run logic inside the process. Depending on the runtime this can escalate directly to remote code execution. Remediation means removing dynamic evaluation of untrusted input and replacing it with safe, data-driven alternatives.

General guidance for the code injection class — the official description and references above are authoritative for this specific CVE. Want a bespoke review and a reviewed fix? Ask our team →

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
Debian LinuxOperating system
Affected:= 9.0= 10.0= 11.0
SmartyApplication
Affected:< 3.1.39

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
Network
Complexity
Low
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

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

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 3.1.39 or later
Fixed in 3.1.39
Vendor patch security.gentoo.org →
Recommended fix High confidence

Smarty 3.1.39 or later

  1. 1. Identify the current Smarty version in use by checking your composer.json, package.json, or installed PHP packages
  2. 2. For PHP/Composer projects: Run 'composer require smarty/smarty:^3.1.39' or 'composer update smarty/smarty --to-version 3.1.39' to upgrade to the fixed release
  3. 3. For Debian systems: Run 'apt-get update && apt-get install libsmarty3' or check for available security updates via 'apt-get upgrade'
  4. 4. After upgrading, clear any compiled template caches (remove the cache directory, typically 'templates_c/')
  5. 5. Verify the new version is installed by checking composer show smarty/smarty or php -m | grep smarty
  6. 6. Test your application to ensure templates render correctly after the upgrade
Caveat Template caching directories should be cleared after upgrade to avoid using old compiled templates; minor template syntax behavior changes may occur between 3.1.x versions

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

We can perform the upgrade in your staging environment and verify nothing breaks — typical engagement from $3,550. Get the upgrade done

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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-2021-26120 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