CWE-325 Base Draft

Missing Cryptographic Step

This vulnerability occurs when a software implementation skips a critical step in a cryptographic process, resulting in security that is significantly weaker than the intended algorithm provides.

Definition

What is CWE-325?

This vulnerability occurs when a software implementation skips a critical step in a cryptographic process, resulting in security that is significantly weaker than the intended algorithm provides.
Cryptographic algorithms are designed as a sequence of specific, interdependent steps. Each step serves a purpose, such as ensuring randomness, preventing pattern analysis, or binding data together securely. When a developer omits one of these steps—whether during key generation, encryption, decryption, or integrity verification—the entire cryptographic operation becomes fragile. The resulting system may appear to function normally but can be easily broken by attackers using well-known techniques, completely undermining the promised security. This flaw often stems from using incomplete code samples, misunderstanding algorithm specifications, or attempting to 'optimize' performance by removing so-called 'unnecessary' operations. To prevent it, developers should rely on reputable, high-level cryptographic libraries rather than implementing algorithms from scratch. Always follow the official algorithm specification or RFC meticulously, and use established test vectors to verify that every required step is correctly executed in the proper order.
Auswirkungen in der Praxis

Real-world CVEs caused by CWE-325

  • CVE-2001-1585

    Missing challenge-response step allows authentication bypass using public key.

Wie Angreifer es ausnutzen

Angreiferpfad Schritt für Schritt

  1. 1

    The example code is taken from the HMAC engine inside the buggy OpenPiton SoC of HACK@DAC'21 [REF-1358]. HAMC is a message authentication code (MAC) that uses both a hash and a secret crypto key. The HMAC engine in HACK@DAC SoC uses the SHA-256 module for the calculation of the HMAC for 512 bits messages.

  2. 2

    However, this HMAC engine cannot handle messages that are longer than 512 bits. Moreover, a complete HMAC will contain an iterate hash function that breaks up a message into blocks of a fixed size and iterates over them with a compression function (e.g., SHA-256). Therefore, the implementation of the HMAC in OpenPiton SoC is incomplete. Such HMAC engines will not be used in real-world applications as the messages will usually be longer than 512 bits. For instance, OpenTitan offers a comprehensive HMAC implementation that utilizes a FIFO for temporarily storing the truncated message, as detailed in [REF-1359].

  3. 3

    To mitigate this, implement the iterative function to break up a message into blocks of a fixed size.

Verwundbares Codebeispiel

Vulnerable Verilog

The example code is taken from the HMAC engine inside the buggy OpenPiton SoC of HACK@DAC'21 [REF-1358]. HAMC is a message authentication code (MAC) that uses both a hash and a secret crypto key. The HMAC engine in HACK@DAC SoC uses the SHA-256 module for the calculation of the HMAC for 512 bits messages.

Verwundbar Verilog 
**logic [511:0] bigData;** 
 ...

 hmac hmac(

```
   .clk_i(clk_i),
   .rst_ni(rst_ni && ~rst_4),
   .init_i(startHash && ~startHash_r),
   .key_i(key),
   .ikey_hash_i(ikey_hash), 
   .okey_hash_i(okey_hash), 
   .key_hash_bypass_i(key_hash_bypass),
```
.message_i(bigData),** 
   .hash_o(hash),
   .ready_o(ready),
   .hash_valid_o(hashValid)
Sicheres Codebeispiel

Secure pseudo

Sicher pseudo 
// Validate, sanitize, or use a safe API before reaching the sink.
function handleRequest(input) {
  const safe = validateAndEscape(input);
  return executeWithGuards(safe);
}
What changed: the unsafe sink is replaced (or the input is validated/escaped) so the same payload no longer triggers the weakness.
Präventions-Checkliste

How to prevent CWE-325

  • Architecture Use safe-by-default frameworks and APIs that prevent the unsafe pattern from being expressible.
  • Implementation Validate input at trust boundaries; use allowlists, not denylists.
  • Implementation Apply the principle of least privilege to credentials, file paths, and runtime permissions.
  • Testing Cover this weakness in CI: SAST rules + targeted unit tests for the data flow.
  • Operation Monitor logs for the runtime signals listed in the next section.
Erkennungssignale

How to detect CWE-325

SAST High

Führe statische Analyse (SAST) auf der Codebasis aus und suche im Datenfluss nach dem unsicheren Muster.

DAST Moderate

Führe dynamische Application-Security-Tests gegen den Live-Endpoint aus.

Runtime Moderate

Beobachte Runtime-Logs auf ungewöhnliche Exception-Traces, fehlerhafte Eingaben oder Versuche, Autorisierung zu umgehen.

Code review Moderate

Code Review: Markiere jeden neuen Code, der Eingaben von dieser Oberfläche ohne validierte Framework-Helper verarbeitet.

Plexicus Auto-Fix

Plexicus erkennt CWE-325 automatisch und öffnet in unter 60 Sekunden einen Fix-PR.

Codex Remedium scannt jeden Commit, identifiziert genau diese Schwachstelle und liefert einen reviewer-ready Pull Request mit dem Patch. Keine Tickets. Keine Hand-offs.

Demo anfordern Plexicus kostenlos testen
Häufig gestellte Fragen

Frequently asked questions

Was ist CWE-325?

This vulnerability occurs when a software implementation skips a critical step in a cryptographic process, resulting in security that is significantly weaker than the intended algorithm provides.

Wie gravierend ist CWE-325?

MITRE hat für diese Schwachstelle keine Exploit-Wahrscheinlichkeit veröffentlicht. Behandle sie als mittlere Auswirkung, bis dein Threat Model anderes belegt.

Welche Sprachen oder Plattformen sind von CWE-325 betroffen?

MITRE lists the following affected platforms: Not Technology-Specific.

Wie kann ich CWE-325 verhindern?

Use safe-by-default frameworks, validate untrusted input at trust boundaries, and apply the principle of least privilege. Cover the data-flow signature in CI with SAST.

Wie erkennt und behebt Plexicus CWE-325?

Die SAST-Engine von Plexicus erkennt die Datenfluss-Signatur von CWE-325 bei jedem Commit. Bei einem Treffer öffnet unser Codex-Remedium-Agent einen Fix-PR mit korrigiertem Code, Tests und einer einzeiligen Zusammenfassung für den Reviewer.

Wo erfahre ich mehr über CWE-325?

MITRE veröffentlicht die kanonische Definition unter https://cwe.mitre.org/data/definitions/325.html. Für ergänzende Hinweise kannst du auch die OWASP- und NIST-Dokumentation heranziehen.

Verwandte Schwachstellen

Weaknesses related to CWE-325

CWE-573 Parent

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CWE-243 Sibling

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CWE-253 Sibling

Incorrect Check of Function Return Value

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CWE-296 Sibling

Improper Following of a Certificate's Chain of Trust

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CWE-304 Sibling

Missing Critical Step in Authentication

This vulnerability occurs when a software authentication process omits a required step, weakening its overall security.

CWE-329 Sibling

Generation of Predictable IV with CBC Mode

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CWE-358 Sibling

Improperly Implemented Security Check for Standard

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Ressourcen

Further reading

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