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The vulnerability, CVE-2021-43826, stems from an unsafe use of the `strcpy` function within the `ldlogger` library, a component executed by the `CodeChecker log` command. A stack-allocated buffer of 4096 bytes (PATH_MAX) is defined to store a file path. The code retrieves the `CC_LOGGER_GCC_LIKE` environment variable and uses `strcpy` to copy its value into this fixed-size buffer without performing any bounds checking. If an attacker supplies a `CC_LOGGER_GCC_LIKE` value longer than 4095 characters, the `strcpy` operation will write beyond the buffer’s boundary, corrupting the stack. This corruption can lead to a crash (Denial of Service) or potentially allow for arbitrary code execution by overwriting critical stack frames, such as the return address, with attacker-controlled data.
Platform: CodeChecker
Version: <= 6.26.1
Vulnerability: Buffer Overflow
Severity: Critical
date: 2021-12-14
Prediction: 2022-01-15
What Undercode Say:
Simulating the vulnerable code logic
cat > vulnerable.c << 'EOF'
include <string.h>
include <stdio.h>
include <unistd.h>
int main(int argc, char argv[]) {
char buffer[bash]; // Fixed-size stack buffer
char env_value = getenv("CC_LOGGER_GCC_LIKE");
if(env_value) {
strcpy(buffer, env_value); // Unsafe strcpy - No bounds check!
printf("Logged: %s\n", buffer);
}
return 0;
}
EOF
Exploitation attempt: Setting a long environment variable
export CC_LOGGER_GCC_LIKE=$(python3 -c "print('A' 5000)")
./vulnerable
How Exploit:
An attacker crafts a malicious build command or environment variable containing a string exceeding 4096 bytes. When this input is processed by the `CodeChecker log` command, it triggers the buffer overflow in the `ldlogger` component. Successful exploitation could crash the CodeChecker process or allow remote code execution with the privileges of the user running CodeChecker.
Protection from this CVE:
Upgrade CodeChecker to version 6.26.2 or later. The patch replaces the unsafe `strcpy` call with strlcpy, which limits the number of characters copied to the size of the destination buffer, preventing the overflow.
Impact:
Critical. The vulnerability allows for denial of service and potential remote code execution, especially in environments where CodeChecker analyzes untrusted codebases or is exposed to malicious user input.
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Sources:
Reported By: github.com
Extra Source Hub:
Undercode
