Difference between revisions of "WAF 330792"
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'''Description''' | '''Description''' | ||
| − | This rule detects when, during the parsing phase of a multipart/request-body, ModSecurity encounters what | + | This rule detects when, during the parsing phase of a multipart/request-body, ModSecurity encounters what the client has presented as a boundary but it is not. Such an event may occur when evasion of ModSecurity is attempted. This is a serious condition, and can mean only one of two things: |
1) An attacker is attempting to bypass the WAF by constructing a body that will not be parsed correctly by the WAF, in hopes of bypassing the WAF. | 1) An attacker is attempting to bypass the WAF by constructing a body that will not be parsed correctly by the WAF, in hopes of bypassing the WAF. | ||
| − | 2) The application is generating non-RFC compliant, or broken message bodies that the WAF is unable to assemble. This can occur with a broken client, buggy library or even a broken connection. | + | |
| + | 2) The client side application (browser, application, etc.) is generating either non-RFC compliant, or broken message bodies that the WAF is unable to assemble. This can occur with a broken client, a non-compliant client, a buggy library or even a broken connection. | ||
'''False Positives''' | '''False Positives''' | ||
| − | Disabling this rule will leave your system open | + | There are no known false positives for this rule. Disabling this rule will leave your system open to multipart bypass attacks, therefore it is highly recommended you first discuss this issue with the applications developers to determine why the format of the request is unparsable, and determine if they can fix their application first. This condition is '''extremely rare''', and it is not recommended that you disable this rule if you have a false positive. We recommend that you first attempt to reproduce this condition. Often this is caused by a broken connection from the client, or a corrupt request. If this is intermittent, then the issue is a broken connection or an intermittent problem on the client that is corrupting the request. |
| + | |||
| + | If this occurs consistently with the client, then it is most likely a bug in the clients implementation for multipart messages and this condition should be reported to the developer for further investigation. | ||
If you believe this is a false positive, please report this to our security team to determine if this is a legitimate case, or if its clever attack on your system. Instructions to report false positives are detailed on the [[Reporting False Positives]] wiki page. If it is a false positive, we will fix the issue in the rules and get a release out to you promptly. | If you believe this is a false positive, please report this to our security team to determine if this is a legitimate case, or if its clever attack on your system. Instructions to report false positives are detailed on the [[Reporting False Positives]] wiki page. If it is a false positive, we will fix the issue in the rules and get a release out to you promptly. | ||
Revision as of 16:02, 7 February 2012
Rule ID
330792
Status
Active rule currently published.
Alert Message
Multipart parser detected a possible unmatched boundary. This may be an impedence mismatch attack, a broken application or a broken connection. This is not a false positive. Check your application or client for errors.
Description
This rule detects when, during the parsing phase of a multipart/request-body, ModSecurity encounters what the client has presented as a boundary but it is not. Such an event may occur when evasion of ModSecurity is attempted. This is a serious condition, and can mean only one of two things:
1) An attacker is attempting to bypass the WAF by constructing a body that will not be parsed correctly by the WAF, in hopes of bypassing the WAF.
2) The client side application (browser, application, etc.) is generating either non-RFC compliant, or broken message bodies that the WAF is unable to assemble. This can occur with a broken client, a non-compliant client, a buggy library or even a broken connection.
False Positives
There are no known false positives for this rule. Disabling this rule will leave your system open to multipart bypass attacks, therefore it is highly recommended you first discuss this issue with the applications developers to determine why the format of the request is unparsable, and determine if they can fix their application first. This condition is extremely rare, and it is not recommended that you disable this rule if you have a false positive. We recommend that you first attempt to reproduce this condition. Often this is caused by a broken connection from the client, or a corrupt request. If this is intermittent, then the issue is a broken connection or an intermittent problem on the client that is corrupting the request.
If this occurs consistently with the client, then it is most likely a bug in the clients implementation for multipart messages and this condition should be reported to the developer for further investigation.
If you believe this is a false positive, please report this to our security team to determine if this is a legitimate case, or if its clever attack on your system. Instructions to report false positives are detailed on the Reporting False Positives wiki page. If it is a false positive, we will fix the issue in the rules and get a release out to you promptly.
Tuning Guidance
If you know that this behaviour is acceptable for your application, you can tune it by identifying the application that is being triggered, and specifically allowing that application to generate bodies the WAF can not examine correctly. Please see the Tuning the Atomicorp WAF Rules page for basic information.
Similar Rules
Knowledge Base Articles
None.
Outside References
None.
