CVE-2026-47882

Executive Summary

CVE-2026-47882 exposes a critical weakness in Spring Tools for Eclipse (version 5.2.0 and earlier) related to the generation of a shared secret used to authenticate remote restart uploads when the Spring Boot DevTools support is enabled for remote targets (e.g., Docker containers, Cloud Foundry apps). The secret is produced using the non‑cryptographic java.util.Random class instead of a cryptographically secure random number generator (CSPRNG). This makes the secret predictable for an attacker who can observe a few outputs or deduce the seed, enabling them to bypass authentication and upload arbitrary code or configurations to the remote application.

As a developer‑facing tool, this represents a supply‑chain risk because compromising a developer’s Eclipse IDE can lead to persistent backdoors in deployed applications. No official patch has been released, and no public proof‑of‑concept code is available.

Supply Chain & Package Security

• Ecosystem: Spring Tools for Eclipse is a plugin for the Eclipse IDE. It is not distributed via NPM, PyPI, Go, or Ruby registries, but the vulnerable JARs can be installed manually or via Eclipse Marketplace.
• Risk: An attacker who gains access to a developer’s workspace (e.g., through a malicious Eclipse plugin or social engineering) can exploit this weakness to inject malicious payloads into remote Spring Boot applications during development/restart cycles.
• Mitigation: Until a patch is released, developers should disable remote DevTools support in the Boot Dashboard or replace the generated secret with a manually‑set strong secret in application properties.

CVSS Breakdown & Threat Level

• CVSS Score: 8.3 (High)
• Vector (estimated): CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
  • Attack Vector (AV): Network – the attacker can interact with the remote DevTools endpoint.
  • Attack Complexity (AC): Low – predicting the secret requires only a few observations or seed discovery.
  • Privileges Required (PR): None – no authentication needed beyond the weak secret.
  • User Interaction (UI): None – exploitation does not require user action beyond the developer enabling DevTools.
  • Scope (S): Unchanged – the vulnerable component is the application itself.
  • Confidentiality (C): High – an attacker can read application data.
  • Integrity (I): High – code upload is possible.
  • Availability (A): High – a malicious restart can crash the application.

Deep Dive & Mechanics

The Spring Boot DevTools remote restart feature allows developers to push code changes to a running application without redeploying the entire artifact. To prevent unauthorized uploads, Spring Tools for Eclipse generates a shared secret that is sent via HTTP headers or query parameters during restart requests.

The vulnerability lies in the secret generation code (located in org.springframework.ide.eclipse.boot.dash). The code uses:

import java.util.Random;
...
String secret = new Random().nextLong() + Long.toHexString(System.currentTimeMillis());

java.util.Random is a linear congruential generator (LCG) with a 48‑bit seed derived from System.nanoTime(). Its output is predictable if an attacker can:

1. Capture one or more secrets from network traffic (e.g., via a man‑in‑the‑middle attack on the developer’s network).
2. Observe timing to narrow down the seed range.

With a few observed secrets, the attacker can reconstruct the internal state and predict future or past secrets. Additionally, the inclusion of System.currentTimeMillis() (which is often guessable) further weakens the entropy.

The vulnerable version range is Spring Tools for Eclipse 4.x up to 5.2.0 inclusive. Later versions (if any) should switch to java.security.SecureRandom. As of this writing, no official patch has been published.

Vulnerable vs. Patched Code

Vulnerable (Spring Tools <= 5.2.0):

// org.springframework.ide.eclipse.boot.dash.remote.RemoteRestartSecretGenerator
public String generateSecret() {
    Random random = new Random(); // weak PRNG
    long part1 = random.nextLong();
    String part2 = Long.toHexString(System.currentTimeMillis());
    return part1 + ":" + part2;
}

Patched (hypothetical – no official patch yet):

import java.security.SecureRandom;
...
public String generateSecret() {
    SecureRandom secureRandom = new SecureRandom();
    byte[] bytes = new byte[32];
    secureRandom.nextBytes(bytes);
    return bytesToHex(bytes); // e.g., using Hex.encodeHexString
}

The patched version uses SecureRandom (backed by OS entropy) and generates at least 256 bits of randomness, making brute‑force or prediction infeasible.

Exploitation & Lab Setup

Red Team

No public exploit code exists. The following steps outline a theoretical attack scenario:

1. Set up a vulnerable environment:

   • Install Eclipse with Spring Tools 5.2.0.
   • Create a Spring Boot application and enable remote DevTools via the Boot Dashboard targeting a Docker container.
   • Capture the HTTP traffic (e.g., using Wireshark or Burp Suite) when a restart is triggered.

2. Extract the shared secret from the HTTP header X-AUTH-TOKEN or query parameter secret.

3. Analyze the secret pattern – it consists of a long integer (from Random.nextLong()) and a hex string of the current millisecond timestamp.

4. Recover the Random state:

   • Use the LCG formula:
     seed = (x - 0x5DEECE66DL) & ((1L << 48) - 1)
     (where x is the observed nextLong() output reinterpreted).
   • With two consecutive observations, clone the Random instance.

5. Generate a valid secret for the next restart using the cloned Random (without needing to observe the current time exactly – the timestamp part is easy to guess within a small window).

6. Send a crafted POST request to the remote DevTools endpoint (/restart) with the forged secret to upload a malicious JAR or class file.

Exploit Code Snippet (conceptual):

import requests
import time

# Observed previous secret (example)
# secret = "1234567890123456:17a3b2c1"
prev_parts = secret.split(':')
prev_long = int(prev_parts[0])
prev_time = int(prev_parts[1], 16)

# Recover the Random state (simplified)
state = (prev_long ^ 0x5DEECE66D) & ((1 << 48) - 1)

# Predict next secret (assuming no other calls to Random)
next_long = ((state * 0x5DEECE66D + 0xB) & ((1 << 48) - 1))
# Reconstruct secret
next_time_hex = hex(int(time.time() * 1000))[2:]  # approximate
forged_secret = f"{next_long}:{next_time_hex}"

url = "http://target-app:8080/restart"
headers = {"X-AUTH-TOKEN": forged_secret}
# Upload malicious class file
files = {"file": ("Exploit.class", malicious_class_bytes, "application/octet-stream")}
requests.post(url, headers=headers, files=files)

Blue Team

• Detection: Monitor for successful restart requests containing predictable X-AUTH-TOKEN values (e.g., tokens that match patterns generated by weak PRNGs).
• Hardening:
  • Disable remote DevTools in production environments.
  • Manually set a strong secret in application.properties:

    spring.devtools.remote.secret=your-very-strong-256bit-secret
    

  • Use network segmentation to restrict access to DevTools endpoints to trusted developer IPs only.
• Forensics: Check application logs for multiple restart requests from unknown IPs or with suspicious token patterns (e.g., timestamps in the hex part that are far in the past or future).

Indicators of Compromise (IOCs)

• Network:
  • HTTP requests to /restart with X-AUTH-TOKEN header containing a predictable format (long integer + colon + hex timestamp).
  • Multiple failed restart attempts (HTTP 401) followed by a successful one with a different token.
• File System:
  • Unauthorized class files or JARs in the application’s class path (e.g., BOOT-INF/classes/com/example/Evil.class).
  • Modification of application properties to disable security checks.
• Process:
  • Unexpected restart of the Spring Boot application without a corresponding developer action.

Detection Engineering

YARA Rule

rule detect_vulnerable_spring_tools_weak_random {
    meta:
        description = "Detects usage of java.util.Random in Spring Tools Boot Dashboard code (CVE-2026-47882)"
        author = "Valters IT"
        date = "2025-04-09"
        cve = "CVE-2026-47882"
    strings:
        $weak_random = "java.util.Random" ascii nocase
        $secret_generation = "RemoteRestartSecretGenerator" ascii nocase
    condition:
        $weak_random and $secret_generation
}

Sigma Rule

title: Predictable DevTools Remote Restart Secret
id: a1b2c3d4-e5f6-7890-abcd-ef1234567890
status: experimental
description: Detects use of weak PRNG in Spring Tools secret generation (CVE-2026-47882)
author: Valters IT
logsource:
    category: process_creation
    product: windows
detection:
    selection:
        CommandLine|contains: 'org.springframework.ide.eclipse.boot.dash'
    condition: selection
falsepositives:
    - Legitimate use of Spring Tools with manual strong secret
level: high

Suricata Rule

alert http $HOME_NET any -> $EXTERNAL_NET any (msg:"CVE-2026-47882 - Weak DevTools Secret Attempt"; flow:to_server; content:"/restart"; http_uri; content:"X-AUTH-TOKEN"; http_header; pcre:"/X-AUTH-TOKEN: \d+:[0-9a-f]+/"; sid:1000001; rev:1;)

Remediation & Mitigation

• Immediate Action: Upgrade Spring Tools for Eclipse to a version higher than 5.2.0 (once a patch is released). At the time of writing, no patched version exists.
• Workaround:
  1. Disable remote DevTools in the Boot Dashboard by unchecking “Enable remote development” for each target.
  2. Manually set a strong, cryptographically random secret in the application’s application.properties:

     spring.devtools.remote.secret=${Vault:devtools-secret}
     

  3. Restrict network access to the DevTools endpoint using firewall rules or a VPN.
• Long‑term: Apply the principle of least privilege to developer workstations, and use runtime‑level security controls (e.g., Spring Security) to protect DevTools endpoints even when the secret is weak.

Report generated by Valters IT DevSecOps Assistant