Automated static analysis, commonly referred to as Static Application Security Testing (SAST), can find some instances of this weakness by analyzing source code (or binary/compiled code) without having to execute it. Typically, this is done by building a model of data flow and control flow, then searching for potentially-vulnerable patterns that connect "sources" (origins of input) with "sinks" (destinations where the data interacts with external components, a lower layer such as the OS, etc.)
CWE-780 Variant Incomplete
Use of RSA Algorithm without OAEP
This vulnerability occurs when an application implements RSA encryption but fails to use Optimal Asymmetric Encryption Padding (OAEP), significantly weakening the cryptographic protection.
Definition
What is CWE-780?
This vulnerability occurs when an application implements RSA encryption but fails to use Optimal Asymmetric Encryption Padding (OAEP), significantly weakening the cryptographic protection.
RSA encryption on its own has mathematical properties that make raw, unpadded messages vulnerable to analysis. Attackers can exploit these patterns to decrypt data without the private key. OAEP adds a layer of random padding before encryption, making every output unique and unpredictable, which is essential for secure RSA implementation in practice.
Without OAEP, encrypted data is far easier to compromise, especially in scenarios involving repeated or predictable messages. While SAST tools can detect this insecure pattern, managing this at scale is difficult; an ASPM like Plexicus can help you track and remediate these flaws across your entire stack, using AI to suggest the specific code fixes needed to implement OAEP correctly.
Real-world impact
Real-world CVEs caused by CWE-780
No public CVE references are linked to this CWE in MITRE's catalog yet.
How attackers exploit it
Step-by-step attacker path
- 1
Identify a code path that handles untrusted input without validation.
- 2
Craft a payload that exercises the unsafe behavior — injection, traversal, overflow, or logic abuse.
- 3
Deliver the payload through a normal request and observe the application's reaction.
- 4
Iterate until the response leaks data, executes attacker code, or escalates privileges.
Vulnerable code example
Vulnerable Java
The example below attempts to build an RSA cipher.
public Cipher getRSACipher() {
Cipher rsa = null;
try {
rsa = javax.crypto.Cipher.getInstance("RSA/NONE/NoPadding");
}
catch (java.security.NoSuchAlgorithmException e) {
log("this should never happen", e);
}
catch (javax.crypto.NoSuchPaddingException e) {
log("this should never happen", e);
}
return rsa;
} Secure code example
Secure Java
While the previous code successfully creates an RSA cipher, the cipher does not use padding. The following code creates an RSA cipher using OAEP.
public Cipher getRSACipher() {
Cipher rsa = null;
try {
rsa = javax.crypto.Cipher.getInstance("RSA/ECB/OAEPWithMD5AndMGF1Padding");
}
catch (java.security.NoSuchAlgorithmException e) {
log("this should never happen", e);
}
catch (javax.crypto.NoSuchPaddingException e) {
log("this should never happen", e);
}
return rsa;
} What changed: the unsafe sink is replaced (or the input is validated/escaped) so the same payload no longer triggers the weakness.
Prevention checklist
How to prevent CWE-780
- 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.
Detection signals
How to detect CWE-780
Plexicus auto-detects CWE-780 and opens a fix PR in under 60 seconds.
Codex Remedium scans every commit, identifies this exact weakness, and ships a reviewer-ready pull request with the patch. No tickets. No hand-offs.
Frequently asked questions What is CWE-780?
How serious is CWE-780?
What languages or platforms are affected by CWE-780?
How can I prevent CWE-780?
How does Plexicus detect and fix CWE-780?
Where can I learn more about CWE-780?
Frequently asked questions
What is CWE-780?
This vulnerability occurs when an application implements RSA encryption but fails to use Optimal Asymmetric Encryption Padding (OAEP), significantly weakening the cryptographic protection.
How serious is CWE-780?
MITRE rates the likelihood of exploit as Medium — exploitation is realistic but typically requires specific conditions.
What languages or platforms are affected by CWE-780?
MITRE has not specified affected platforms for this CWE — it can apply across most application stacks.
How can I prevent CWE-780?
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.
How does Plexicus detect and fix CWE-780?
Plexicus's SAST engine matches the data-flow signature for CWE-780 on every commit. When a match is found, our Codex Remedium agent opens a fix PR with the corrected code, tests, and a one-line summary for the reviewer.
Where can I learn more about CWE-780?
MITRE publishes the canonical definition at https://cwe.mitre.org/data/definitions/780.html. You can also reference OWASP and NIST documentation for adjacent guidance.
Related weaknesses
Weaknesses related to CWE-780
CWE-327 Parent
Use of a Broken or Risky Cryptographic Algorithm
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CWE-1240 Sibling
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CWE-328 Sibling
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CWE-916 Sibling
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