CVE-2024-56522Network attack vector

Unexpected method invocation via loose HMAC comparison

Published Dec 27, 2024 · Updated Nov 3, 2025

Type juggling in TCPDF before 6.8.0 allows remote attackers to invoke allowlisted PDF methods via a crafted TCPDF HTML tag. unserializeTCPDFtag parses a supplied hash and compares it with the expected SHA-256 HMAC using PHP's loose != operator, allowing an incorrect match. The path requires K_TCPDF_CALLS_IN_HTML and untrusted HTML during PDF generation; a bypass invokes an allowlisted TCPDF method with attacker-chosen arguments.

CVSS severity7.5
High
EPSS probability0.63%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Type juggling in TCPDF before 6.8.0 allows remote attackers to invoke allowlisted PDF methods via a crafted TCPDF HTML tag. unserializeTCPDFtag parses a supplied hash and compares it with the expected SHA-256 HMAC using PHP's loose != operator, allowing an incorrect match. The path requires K_TCPDF_CALLS_IN_HTML and untrusted HTML during PDF generation; a bypass invokes an allowlisted TCPDF method with attacker-chosen arguments.

The record

CVE
CVE-2024-56522
Published
Dec 27, 2024
Updated
Nov 3, 2025
Vendor
Tecnick.com LTD
Product
TCPDF
Classifications
CWE-843, CWE-697, T1190
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Dec 27, 2024CVE publishedPublication date reported by the CVE source.
  2. Nov 3, 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=0 <6.8.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Tecnick.com LTD · TCPDFversion=0 <6.8.0

Published CVSS scores

7.5CISA-ADPCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

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-843Access of Resource Using Incompatible Type ('Type Confusion')
CWE-697Incorrect Comparison
T1190Exploit Public-Facing Application

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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