CVE-2021-23803Public exploitNetwork attack vector

Remote code execution via control-character function names

Published Dec 17, 2021 · Updated Sep 16, 2024

Access control bypass in Nette Foundation Latte before 2.10.6 allows remote attackers to call disallowed PHP functions through templates. The parser accepted ASCII control characters after a function identifier, causing sandbox allowFunctions validation to miss the name that PHP ultimately invokes. Exploitation requires an application to render attacker-controlled Latte templates with sandbox mode and a restrictive allowFunctions policy.

CVSS severity9.8
Critical
EPSS probability1.58%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Access control bypass in Nette Foundation Latte before 2.10.6 allows remote attackers to call disallowed PHP functions through templates. The parser accepted ASCII control characters after a function identifier, causing sandbox allowFunctions validation to miss the name that PHP ultimately invokes. Exploitation requires an application to render attacker-controlled Latte templates with sandbox mode and a restrictive allowFunctions policy.

The record

CVE
CVE-2021-23803
Published
Dec 17, 2021
Updated
Sep 16, 2024
Vendor
Nette Foundation
Product
Latte
Classifications
CWE-284, CWE-863, T1059
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Dec 17, 2021CVE publishedPublication date reported by the CVE source.
  2. Sep 16, 2024Record 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=unspecified <2.10.6

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Nette Foundation · Latteversion=unspecified <2.10.6

Published CVSS scores

9.8NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
7.5NIST NVDAV:N/AC:L/Au:N/C:P/I:P/A:P
9.8SnykCVSS:3.1/AV:N/AC:L/PR:N/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.

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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 exploitPublished

Weakness, pattern, technique

CWE-284Improper Access Control
CWE-863Incorrect Authorization
T1059Command and Scripting Interpreter

Public exploit references

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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