In early 2025, security researchers at Wiz uncovered a critical vulnerability in AWS CodeBuild that could have enabled attackers to inject malicious code into the AWS JavaScript SDK—a package used by millions of cloud environments worldwide. The flaw, dubbed "CodeBreach," stemmed from a deceptively simple mistake: unanchored regular expressions in webhook filters that validated GitHub user identities.
This was not merely a hypothetical vulnerability; Wiz demonstrated a working proof-of-concept under controlled conditions. The vulnerability affected four high-value AWS repositories, including the widely-deployed aws/aws-sdk-js-v3. If exploited, this flaw could have allowed attackers to steal privileged access tokens, execute arbitrary build code, and potentially distribute backdoored software—though AWS confirmed no malicious exploitation occurred. While Wiz responsibly disclosed the issue before any malicious exploitation occurred, CodeBreach serves as a stark reminder that even the world's largest cloud provider isn't immune to CI/CD security lapses—and that small configuration errors can create supply chain catastrophes.
This analysis examines how the vulnerability worked, why it matters for your organization's security posture, and what lessons security teams can extract from AWS's rapid response.
Understanding the CodeBreach Vulnerability
CodeBreach exploited a fundamental weakness in how AWS CodeBuild validated incoming webhook requests from GitHub. The vulnerability centered on access control logic that determined which GitHub users could trigger privileged build pipelines.
The Regex Anchoring Problem
AWS CodeBuild uses webhook filters to restrict which GitHub actors can initiate builds in sensitive repositories. These filters employed regular expressions to match the ACTOR_ID parameter against approved GitHub user identifiers. However, the regex patterns lacked proper anchoring—they didn't use start (^) and end ($) anchors to ensure complete string matching.
This oversight created a pattern-matching loophole. Instead of verifying that the entire ACTOR_ID exactly matched an authorized user, the filter only checked whether the approved ID appeared anywhere within the submitted value. An attacker could craft a malicious GitHub username containing a legitimate maintainer's ID as a substring, bypassing the security check entirely.
GitHub ID Eclipse Attack Vector
The exploitation technique, as demonstrated by Wiz researchers, relied on GitHub’s namespace flexibility. Attackers could mass-register GitHub Apps or user accounts with names strategically designed to include authorized maintainer IDs. For example, if a legitimate maintainer had ID 12345, an attacker might create 12345-malicious or exploit-12345-backdoor.
When these specially-crafted accounts submitted pull requests or triggered webhooks, CodeBuild's flawed regex matched the embedded legitimate ID and granted access. The system essentially confused the attacker's account for an authorized maintainer because it found the expected pattern within the malicious string.
Table: Vulnerable vs. Secure Regex Patterns
| Pattern Type | Example | Matches Malicious Input | Secure |
|---|---|---|---|
| Unanchored | 12345 | Yes - matches evil-12345 | No |
| Partially Anchored | ^12345 | Yes - matches 12345-malicious | No |
| Fully Anchored | ^12345$ | No - exact match only | Yes |
| Named Pattern | ^(12345|67890)$ | No - explicit allowlist | Yes |
Impact on High-Value Repositories
The vulnerability affected four critical AWS repositories, with aws/aws-sdk-js-v3 representing the highest-risk target. This JavaScript SDK powers the AWS Management Console and serves as a foundational dependency for countless cloud applications. If exploited, the issue could have enabled several attack scenarios:
- Build Code Injection: Attackers could execute arbitrary code within AWS's build environment, accessing secrets, credentials, and internal systems
- Token Theft: The build environment contained a Personal Access Token for the aws-sdk-js-automation account with write permissions across multiple repositories
- Supply Chain Poisoning: With stolen credentials, attackers could commit backdoored code directly to production branches, distributing malware to downstream consumers
The aws/aws-lc repository presented additional risk. This cryptographic library underpins security-critical functions across AWS services, and a compromise could have significantly increased risk to those components
The Attack Chain: From Discovery to Potential Compromise
Wiz's research team demonstrated a complete proof-of-concept attack chain, stopping deliberately short of actual exploitation. Their findings revealed how quickly initial access could escalate to platform-wide compromise.
Initial Access and Reconnaissance
The attack began with reconnaissance of AWS's public repositories. Researchers identified CodeBuild configurations that used webhook filters for access control. By examining the build configuration files and testing various GitHub account names, they determined which patterns the regex filters expected.
Creating test GitHub accounts with embedded legitimate IDs, researchers confirmed the pattern-matching flaw. The system accepted their crafted usernames because the unanchored regex found the expected maintainer ID somewhere in the string. This initial foothold required no sophisticated exploits—just careful observation and GitHub account creation.
Privilege Escalation Through Build Execution
Once inside the build pipeline, attackers gained access to a privileged execution environment. CodeBuild environments often contain sensitive credentials needed to perform their automated tasks: publishing packages, updating documentation, or deploying infrastructure.
In this case, the build environment exposed the aws-sdk-js-automation Personal Access Token. This credential provided elevated write access to the affected SDK repositories, but did not grant unrestricted access across all AWS repositories. The escalation from "unauthorized webhook trigger" to "repository maintainer" took minutes, not days.
Potential Supply Chain Contamination
With stolen credentials, attackers could have pursued several contamination strategies:
- Direct Commit Poisoning: Push malicious commits directly to main branches, bypassing code review processes
- Dependency Confusion: Inject compromised dependencies that existing build processes would automatically incorporate
- Long-Term Persistence: Create backdoors in rarely-audited configuration files or build scripts
- Staged Payloads: Commit seemingly benign code that activates malicious functionality only under specific conditions
The aws-sdk-js-v3 package receives millions of downloads monthly. A successful backdoor could have propagated to customer environments worldwide before detection, creating incident response challenges at unprecedented scale.
Table: Attack Progression Timeline
| Phase | Activity | Time Required | Impact Level |
|---|---|---|---|
| Reconnaissance | Identify vulnerable repos and regex patterns | 1-4 hours | Low |
| Initial Access | Create malicious GitHub account, trigger build | 15-30 minutes | Medium |
| Credential Theft | Extract PAT from build environment | 5-10 minutes | High |
| Lateral Movement | Access additional repos with stolen token | 10-30 minutes | Critical |
| Payload Deployment | Commit backdoored code to production | 15-60 minutes | Critical |
All time estimates reflect proof-of-concept demonstrations conducted by Wiz researchers and do not represent observed real-world attacks
Why Wiz Stopped Short of Full Exploitation
Responsible disclosure practices guided Wiz's research methodology. After confirming the vulnerability's exploitability, researchers immediately contacted AWS's security team rather than proceeding to actual code injection. They provided detailed technical documentation, proof-of-concept demonstrations, and remediation recommendations.
This ethical approach protected AWS customers while still demonstrating the severity of the issue. It also established a collaborative relationship that enabled AWS to respond quickly and comprehensively.
AWS's Response and Remediation Strategy
AWS treated CodeBreach as a critical security incident, implementing fixes and protective measures within approximately 48 hours of disclosure. Their response demonstrated mature incident handling and commitment to transparency.
Immediate Technical Fixes
AWS's engineering team corrected the regex anchoring issues across all affected repositories. The updated patterns used proper start and end anchors (^ and $) to ensure exact string matching. This prevented the substring exploitation technique while maintaining legitimate functionality.
Beyond regex fixes, AWS implemented additional validation layers. The revised webhook handlers now verify GitHub account age, reputation signals, and historical activity patterns. These defense-in-depth measures make abuse harder even if future regex errors occur.
Credential Rotation and Secret Management
AWS immediately revoked the exposed aws-sdk-js-automation Personal Access Token and all related credentials that might have been compromised. New tokens were generated with more restrictive permissions following the principle of least privilege.
The team also implemented enhanced memory protections for build environments. Sensitive credentials now use time-limited tokens with automatic rotation, reducing the window of opportunity if future leaks occur. Build logs underwent sanitization to prevent accidental credential exposure.
Customer Impact Assessment
AWS conducted comprehensive log analysis to verify that no unauthorized access had occurred before the fix. Their investigation confirmed that only Wiz's controlled proof-of-concept attempts triggered the vulnerable code path. No customer environments showed signs of compromise, and no malicious packages entered distribution channels.
This thorough assessment allowed AWS to provide definitive assurance to customers while identifying areas for improved monitoring. The incident highlighted gaps in webhook activity logging that have since been addressed.
Table: AWS Remediation Measures
| Category | Action Taken | Timeline | Effectiveness |
|---|---|---|---|
| Configuration | Fixed regex anchoring in webhook filters | 12-24 hours | Complete mitigation |
| Credentials | Revoked and rotated all exposed tokens | 24-36 hours | Eliminated theft risk |
| Monitoring | Enhanced logging for webhook activities | 36-48 hours | Improved detection |
| Architecture | Implemented least-privilege token scoping | 48-72 hours | Reduced blast radius |
Lessons for CI/CD Security and Supply Chain Defense
CodeBreach offers actionable insights for security teams managing their own CI/CD pipelines and software supply chains. The vulnerability's root causes and exploitation techniques apply broadly across modern development environments.
Regex Validation Requires Precision
Input validation with regular expressions demands careful design and testing. Security-critical patterns must use proper anchoring to prevent substring matching attacks. Development teams should treat regex patterns as security controls, subjecting them to the same review rigor as authentication or authorization code.
Pro Tip: Always anchor security-relevant regex patterns with ^ and $. Test your patterns against malicious inputs that contain valid substrings in unexpected positions.
Webhook Security Often Gets Overlooked
Webhooks represent trust boundaries that deserve explicit security controls. Many organizations configure webhook endpoints without thorough validation of sender identity, payload integrity, or request authorization. Attackers increasingly target these integration points as weak spots in otherwise hardened infrastructure.
Implement multiple validation layers for webhooks:
- Cryptographic signature verification for payload authenticity
- IP address allowlisting where feasible
- Rate limiting to prevent abuse
- Comprehensive logging for forensic analysis
- Regular security reviews of webhook configurations
CI/CD Privilege Boundaries Need Defense in Depth
Build environments often accumulate excessive privileges over time. As pipelines evolve, credentials get added for new integrations but rarely removed or scoped down. This privilege creep creates attractive targets for attackers who gain initial access.
Apply least-privilege principles aggressively:
- Scope credentials to specific repositories and operations
- Use short-lived tokens with automatic rotation
- Separate build, test, and deployment credentials
- Implement just-in-time privilege elevation for sensitive operations
- Regularly audit and prune unused credentials
Supply Chain Security Extends to Internal Infrastructure
Organizations often focus supply chain security efforts on third-party dependencies while overlooking risks in their own development infrastructure. Internal CI/CD systems can become supply chain attack vectors if compromised, especially for organizations that publish libraries, SDKs, or services consumed by customers.
Important: Your internal build systems are part of your customers' supply chain. Apply the same security rigor to CI/CD infrastructure that you would to production systems handling customer data.
Monitoring and Detection Gaps Delay Response
Many organizations lack adequate visibility into CI/CD activities. Build logs often capture stdout but miss security-relevant events like authentication attempts, credential access, or unusual API calls. This monitoring gap extends detection timelines and complicates incident response.
Implement comprehensive CI/CD observability:
- Log all authentication and authorization decisions
- Monitor for unusual build patterns or timing anomalies
- Alert on credential access outside normal workflows
- Correlate build activity with code changes and approvals
- Establish baseline metrics for anomaly detection
Table: CI/CD Security Controls Comparison
| Control Type | Traditional Approach | Enhanced Security Posture |
|---|---|---|
| Access Control | GitHub team membership | Multi-factor validation with anchored regex |
| Credentials | Long-lived static tokens | Short-lived, auto-rotating, least-privilege tokens |
| Validation | Single authentication check | Layered verification with reputation signals |
| Monitoring | Basic build logs | Comprehensive security event logging with SIEM integration |
| Response | Manual credential rotation | Automated detection and response workflows |
Key Takeaways
- Regex anchoring errors in webhook filters can create critical access control bypasses if exploited, allowing attackers to impersonate legitimate users through carefully crafted account names
- CI/CD environments require defense-in-depth security controls including input validation, credential management, monitoring, and least-privilege access policies
- Supply chain attacks increasingly target development infrastructure rather than just third-party dependencies, making internal CI/CD security essential for organizations that distribute software
- Rapid response to security disclosures minimizes customer impact as demonstrated by AWS's 48-hour remediation timeline and comprehensive log analysis
- Build environment privileges should follow least-privilege principles with short-lived tokens, automatic rotation, and careful scoping to specific repositories and operations
- Comprehensive monitoring fills detection gaps by logging security-relevant events beyond standard build output, enabling faster incident identification and response
Conclusion
CodeBreach demonstrates how seemingly minor configuration errors can create catastrophic security exposures. An unanchored regular expression—a mistake that might take 30 seconds to introduce during routine configuration—created a pathway to potentially compromise millions of cloud environments through supply chain contamination.
The incident underscores evolving threat models for cloud-native organizations. Attackers increasingly recognize that compromising development infrastructure offers better returns than targeting individual applications. CI/CD pipelines, build environments, and artifact repositories represent high-value targets because successful exploitation cascades across entire customer bases.
For security teams, CodeBreach offers a clear mandate: treat CI/CD infrastructure with the same security rigor applied to production systems. Implement proper input validation, enforce least-privilege access, maintain comprehensive monitoring, and conduct regular security reviews of build configurations. The alternative—discovering vulnerabilities after exploitation rather than before—carries unacceptable risks in today's interconnected software ecosystem.
Frequently Asked Questions
Q: How can I check if my own CI/CD pipelines have similar regex vulnerabilities?
A: Audit all webhook filters, access control patterns, and input validation logic for proper regex anchoring. Test each pattern with malicious inputs that contain valid substrings in unexpected positions. Consider implementing automated security scanning for your CI/CD configuration files.
Q: What's the difference between this and other recent supply chain attacks like SolarWinds or 3CX?
A: CodeBreach targeted the software development infrastructure directly rather than inserting backdoors into legitimate updates post-build. While SolarWinds involved compromising the build environment to inject malicious code, CodeBreach could have enabled this through a simple configuration error rather than sophisticated intrusion. The attack surface was different, but the potential impact—mass distribution of compromised software—remained similar.
Q: Should we disable webhooks entirely to prevent these attacks?
A: Disabling webhooks removes useful automation without addressing underlying security gaps. Instead, implement proper webhook security controls: cryptographic signature verification, anchored regex validation, IP allowlisting where feasible, comprehensive logging, and regular configuration audits. Defense-in-depth approaches provide security without sacrificing functionality.
Q: How quickly should organizations rotate credentials after potential CI/CD compromise?
A: Immediate rotation is critical. Assume that any credential accessible in a compromised build environment has been stolen. Rotate within hours, not days, and implement enhanced monitoring for suspicious activity using old credentials. Establish incident response playbooks that include automated credential rotation to accelerate response timelines.
Q: What compliance implications does CodeBreach have for organizations using AWS services?
A: While AWS confirmed no customer environments were impacted, the incident highlights supply chain risk management requirements in frameworks like SOC 2, ISO 27001, and NIST CSF. Organizations should review their vendor risk assessments, ensure AWS security notifications are monitored, and document how third-party vulnerabilities are tracked and addressed in their security programs.