CVE-2021-29454Network attack vector

Arbitrary PHP execution via unvalidated math expressions

Published Jan 10, 2022 · Updated Apr 23, 2025

Code injection in Smarty before 3.1.42 and 4.0.0 through 4.0.1 allows attackers to execute arbitrary PHP via crafted math strings. The smarty_function_math function passes its equation parameter directly to PHP eval after checks that do not enforce a valid mathematical grammar. Reachability requires a template author or an embedding application to pass attacker-controlled data as the equation, after which code runs with the PHP process's privileges.

CVSS severity8.1
High
EPSS probability1.93%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Code injection in Smarty before 3.1.42 and 4.0.0 through 4.0.1 allows attackers to execute arbitrary PHP via crafted math strings. The smarty_function_math function passes its equation parameter directly to PHP eval after checks that do not enforce a valid mathematical grammar. Reachability requires a template author or an embedding application to pass attacker-controlled data as the equation, after which code runs with the PHP process's privileges.

The record

CVE
CVE-2021-29454
Published
Jan 10, 2022
Updated
Apr 23, 2025
Vendor
Smarty
Product
Smarty
Classifications
CWE-74, T1059
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jan 10, 2022CVE publishedPublication date reported by the CVE source.
  2. Apr 23, 2025Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=< 3.1.42
  2. Affected versionversion=>= 4.0.0, < 4.0.2

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Smarty · Smartyversion=< 3.1.42; version=>= 4.0.0, < 4.0.2

Published CVSS scores

8.1GitHub, Inc.CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:N
6.5NIST NVDAV:N/AC:L/Au:S/C:P/I:P/A:P
8.8NIST NVDCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-74Improper Neutralization of Special Elements in Output Used by a Downstream Component ('Injection')
T1059Command and Scripting Interpreter

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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