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codeql/cpp/ql/src/Security/CWE/CWE-079/CgiXss.ql
2026-03-13 10:01:02 +00:00

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/**
* @name CGI script vulnerable to cross-site scripting
* @description Writing user input directly to a web page
* allows for a cross-site scripting vulnerability.
* @kind path-problem
* @problem.severity error
* @security-severity 7.8
* @precision high
* @id cpp/cgi-xss
* @tags security
* external/cwe/cwe-079
*/
import cpp
import semmle.code.cpp.commons.Environment
import semmle.code.cpp.ir.dataflow.TaintTracking
import semmle.code.cpp.ir.IR
import Flow::PathGraph
/** A call that prints its arguments to `stdout`. */
class PrintStdoutCall extends FunctionCall {
PrintStdoutCall() { this.getTarget().hasGlobalOrStdName(["puts", "printf"]) }
}
/** A read of the QUERY_STRING environment variable */
class QueryString extends EnvironmentRead {
QueryString() { this.getEnvironmentVariable() = "QUERY_STRING" }
}
module Config implements DataFlow::ConfigSig {
predicate isSource(DataFlow::Node node) { node.asIndirectExpr() instanceof QueryString }
predicate isSink(DataFlow::Node node) {
exists(PrintStdoutCall call | call.getAnArgument() = [node.asIndirectExpr(), node.asExpr()])
}
predicate isBarrier(DataFlow::Node node) {
isSink(node) and node.asExpr().getUnspecifiedType() instanceof ArithmeticType
or
node.asCertainDefinition().getUnspecifiedType() instanceof ArithmeticType
}
predicate observeDiffInformedIncrementalMode() { any() }
Location getASelectedSourceLocation(DataFlow::Node source) {
exists(QueryString query | result = query.getLocation() | query = source.asIndirectExpr())
}
}
module Flow = TaintTracking::Global<Config>;
from QueryString query, Flow::PathNode sourceNode, Flow::PathNode sinkNode
where
Flow::flowPath(sourceNode, sinkNode) and
query = sourceNode.getNode().asIndirectExpr()
select sinkNode.getNode(), sourceNode, sinkNode, "Cross-site scripting vulnerability due to $@.",
query, "this query data"