Authentication Bypass by Capture-replay
Weakness ID: 294 (Weakness Base)Status: Incomplete
+ Description

Description Summary

A capture-replay flaw exists when the design of the software makes it possible for a malicious user to sniff network traffic and bypass authentication by replaying it to the server in question to the same effect as the original message (or with minor changes).

Extended Description

Capture-replay attacks are common and can be difficult to defeat without cryptography. They are a subset of network injection attacks that rely on observing previously-sent valid commands, then changing them slightly if necessary and resending the same commands to the server.

+ Time of Introduction
  • Architecture and Design
+ Applicable Platforms



+ Common Consequences

Messages sent with a capture-relay attack allow access to resources which are not otherwise accessible without proper authentication.

+ Likelihood of Exploit


+ Demonstrative Examples

Example 1

Example Languages: C and C++ 
unsigned char *simple_digest(char *alg,char *buf,unsigned int len, int *olen) {
const EVP_MD *m; EVP_MD_CTX ctx;
unsigned char *ret;
if (!(m = EVP_get_digestbyname(alg))) return NULL;
if (!(ret = (unsigned char*)malloc(EVP_MAX_MD_SIZE))) return NULL;
EVP_DigestInit(&ctx, m);
return ret;
unsigned char *generate_password_and_cmd(char *password_and_cmd) {
Example Language: Java 
String command = new String("some cmd to execute & the password")
MessageDigest encer = MessageDigest.getInstance("SHA");
byte[] digest = encer.digest();
+ Observed Examples
CVE-2005-3435product authentication succeeds if user-provided MD5 hash matches the hash in its database; this can be subjected to replay attacks.
+ Potential Mitigations

Phase: Architecture and Design

Utilize some sequence or time stamping functionality along with a checksum which takes this into account in order to ensure that messages can be parsed only once.

Phase: Architecture and Design

Since any attacker who can listen to traffic can see sequence numbers, it is necessary to sign messages with some kind of cryptography to ensure that sequence numbers are not simply doctored along with content.

+ Relationships
NatureTypeIDNameView(s) this relationship pertains toView(s)
ChildOfWeakness ClassWeakness Class592Authentication Bypass Issues
Development Concepts (primary)699
Research Concepts (primary)1000
+ Taxonomy Mappings
Mapped Taxonomy NameNode IDFitMapped Node Name
PLOVERAuthentication bypass by replay
+ Related Attack Patterns
CAPEC-IDAttack Pattern Name
(CAPEC Version: 1.4)
94Man in the Middle Attack
60Reusing Session IDs (aka Session Replay)
102Session Sidejacking
+ Content History
Submission DateSubmitterOrganizationSource
PLOVERExternally Mined
Modification DateModifierOrganizationSource
2008-09-08CWE Content TeamMITREInternal
updated Common Consequences, Relationships, Other Notes, Taxonomy Mappings
2009-05-27CWE Content TeamMITREInternal
updated Related Attack Patterns
2009-07-27CWE Content TeamMITREInternal
updated Description, Other Notes, Potential Mitigations
2009-10-29CWE Content TeamMITREInternal
updated Observed Examples