HOMEVULNERABILITIESCVE-2021-21408
HIGH

CVE-2021-21408

CWE-20Published: January 10, 2022· Updated: Jun 17, 2026

8.8
CVSS v3.1

Official Description

Smarty is a template engine for PHP, facilitating the separation of presentation (HTML/CSS) from application logic. Prior to versions 3.1.43 and 4.0.3, template authors could run restricted static php methods. Users should upgrade to version 3.1.43 or 4.0.3 to receive a patch.

NVD Source

Technical Analysis

CVE-2021-21408 can be exploited remotely over the network without requiring physical or adjacent access, significantly expanding the attack surface for threat actors.

Exploitation requires low privileges, which limits the exposure to scenarios where an attacker has already gained initial access.

A successful exploit results in complete confidentiality breach (data exposure), full integrity compromise (data manipulation), availability disruption (denial of service), with a CVSS base score of 8.8.

CVSS v3.1 Vector Breakdown

Exploitability
Attack VectorNetwork
Attack ComplexityLow
Privileges Req.Low
User InteractionNone
ScopeUnchanged
Impact
ConfidentialityHigh
IntegrityHigh
AvailabilityHigh
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Affected Vendors & Products

Debian1 product(s)
debian linux
Fedora1 product(s)
fedora
smarty1 product(s)
smarty
Source: NVD CPE · 6 total CPE entries

Exploit & PoC Resources

NO KNOWN EXPLOITNo public exploit confirmed at this time
Exploit-DB
Offensive Security exploit database
GitHub PoC Search
Community PoC repositories
Rapid7 / Metasploit
Metasploit module search
PacketStorm
Security advisories & exploits
NVD Detail
Official NIST entry
MITRE CVE
CVE Program entry
External links open in a new tab. Always verify in a controlled environment before use.

Official Patches & Advisories

PATCHhttps://github.com/smarty-php/smarty/commit/19ae410bf56007a5ef24441cdc6414619cfaf664
PATCHhttps://github.com/smarty-php/smarty/commit/19ae410bf56007a5ef24441cdc6414619cfaf664
ADVISORYhttps://github.com/smarty-php/smarty/releases/tag/v3.1.43
ADVISORYhttps://github.com/smarty-php/smarty/releases/tag/v4.0.3
ADVISORYhttps://github.com/smarty-php/smarty/security/advisories/GHSA-4h9c-v5vg-5m6m
ADVISORYhttps://lists.debian.org/debian-lts-announce/2022/05/msg00005.html
ADVISORYhttps://security.gentoo.org/glsa/202209-09
ADVISORYhttps://www.debian.org/security/2022/dsa-5151
ADVISORYhttps://github.com/smarty-php/smarty/releases/tag/v3.1.43
ADVISORYhttps://github.com/smarty-php/smarty/releases/tag/v4.0.3
ADVISORYhttps://github.com/smarty-php/smarty/security/advisories/GHSA-4h9c-v5vg-5m6m
ADVISORYhttps://lists.debian.org/debian-lts-announce/2022/05/msg00005.html
ADVISORYhttps://security.gentoo.org/glsa/202209-09
ADVISORYhttps://www.debian.org/security/2022/dsa-5151

All References (18)

→
https://github.com/smarty-php/smarty/commit/19ae410bf56007a5ef24441cdc6414619cfaf664Patch · Third Party Advisory
→
https://github.com/smarty-php/smarty/releases/tag/v3.1.43Release Notes · Third Party Advisory
→
https://github.com/smarty-php/smarty/releases/tag/v4.0.3Release Notes · Third Party Advisory
→
https://github.com/smarty-php/smarty/security/advisories/GHSA-4h9c-v5vg-5m6mThird Party Advisory
→
https://lists.debian.org/debian-lts-announce/2022/05/msg00005.htmlMailing List · Third Party Advisory
→
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/BRAJVDRGCIY5UZ2PQHKDTT7RMKG6WJQQ/
→
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/L777JIBIWJV34HS7LXPIDWASG7TT4LNI/
→
https://security.gentoo.org/glsa/202209-09Third Party Advisory
→
https://www.debian.org/security/2022/dsa-5151Third Party Advisory
→
https://github.com/smarty-php/smarty/commit/19ae410bf56007a5ef24441cdc6414619cfaf664Patch · Third Party Advisory
→
https://github.com/smarty-php/smarty/releases/tag/v3.1.43Release Notes · Third Party Advisory
→
https://github.com/smarty-php/smarty/releases/tag/v4.0.3Release Notes · Third Party Advisory
→
https://github.com/smarty-php/smarty/security/advisories/GHSA-4h9c-v5vg-5m6mThird Party Advisory
→
https://lists.debian.org/debian-lts-announce/2022/05/msg00005.htmlMailing List · Third Party Advisory
→
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/BRAJVDRGCIY5UZ2PQHKDTT7RMKG6WJQQ/

Quick Facts

CVE IDCVE-2021-21408
CVSS Score8.8 / 10
SeverityHIGH
WeaknessCWE-20
CISA KEVNo
Affected3 vendor(s)
PublishedJan 10, 2022

Related CVEs (CWE-20)

CVE-2008-4641
10.0
CVE-2008-5014
10.0
CVE-2008-4404
10.0
CVE-2008-3479
10.0
CVE-2008-4358
10.0
CVE-2009-0258
10.0

Recommended Actions

  • →Apply vendor patches immediately
  • →Monitor CVE-2021-21408 in threat intel feeds
  • →Review IDS/IPS signatures for exploitation attempts
Data sourced from NVD (NIST), CISA KEV, and EPSS (FIRST). Analysis generated by CTIWATCH.COM. CVE data is provided under the NVD usage policy.
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