Hackers Exploit Pandoc CVE-2025-51591: Protect AWS IMDS and EC2 IAM Credentials

Hackers Exploit Pandoc CVE-2025-51591: Protect AWS IMDS and EC2 IAM Credentials

Security teams around the world are focused on a convergence of software supply chain risk and cloud credential exposure. The Pandoc vulnerability tracked as CVE-2025-51591 has renewed attention on how a single flawed document processor can become a stepping stone to sensitive data on AWS EC2 instances. In practice, attackers are looking to leverage a successful Pandoc exploit to reach the AWS Instance Metadata Service (IMDS) and obtain ephemeral credentials tied to EC2 IAM roles. This isn’t theoretical: it’s a reminder that the weakest link in a cloud-native workflow can be a process with high privileges.

What the exploit might look like

Pandoc’s role in many build pipelines, content-rendering services, and CI tasks makes it a tempting target when a vulnerability exists. CVE-2025-51591 is described as enabling an attacker to influence Pandoc’s processing path through crafted input. In an environment where Pandoc runs with sufficient privileges or inside a container that can reach the instance’s metadata service, a trained attacker could cause Pandoc to perform network calls or affect how data is handled in memory. On an EC2 host, this can translate into attempts to query the 169.254.169.254 metadata endpoint and, if credentials are accessible, to exfiltrate them or use them to assume additional roles.

Security researchers emphasize that the metadata service is a trusted source for legitimate workloads; therefore, any process with the ability to reach IMDS can pose a risk if it can surface credentials or tokens in logs, pipes, or outbound traffic.

Why AWS IMDS and EC2 IAM credentials are a critical target

EC2 instances obtain temporary credentials from the Instance Metadata Service via IAM roles attached to the instance. Those credentials enable access to AWS services without embedding long-lived keys. When a vulnerability like CVE-2025-51591 grants an attacker control over a document processing workflow, a foothold inside the host can become a credential pipeline. If Pandoc is used in a way that processes user-supplied content within a container or a service account with broad permissions, an attacker who compromises that process may be able to read metadata credentials or trigger token retrieval sequences that expose access keys to a remote observer.

Practical mitigations you can implement today

• Patch Pandoc immediately to the version that contains the fix for CVE-2025-51591. If a patch isn’t yet available in your downstream images, isolate Pandoc to a restricted environment where it cannot reach sensitive endpoints.
• Enforce IMDSv2 only and require a valid token before any metadata call. In practice, configure the instance metadata options to mandatorily use IMDSv2 and set a minimal hop limit (usually 1) to constrain where credentials can be exposed from the host.
• Limit access to IMDS from workloads by default. Block unnecessary egress to 169.254.169.254, and segment containerized workloads so that processes running Pandoc do not share a network path with metadata traffic unless explicitly required.
• Adopt IAM Roles for EC2 with least privilege and avoid embedding credentials. Use tightly scoped roles and enable automatic rotation. Review each role’s permissions to ensure they align with the actual needs of the workload.
• Sandbox and isolate document processing—run Pandoc inside constrained containers or firewalled environments with strict file-system and network permissions. Validate and sanitize all input before processing, and avoid processing untrusted content in privileged contexts.

Detection and response playbooks

To detect signs of exploitation, monitor for unusual activity from Pandoc processes, such as unexpected network connections directed at the metadata IP, or spikes in traffic from a host that otherwise doesn’t access external data sources. Leverage endpoint security that tracks process trees and network connections, and enable anomaly detection for containerized workloads. In AWS, correlate CloudTrail logs with IAM role usage and GuardDuty findings that could indicate credential exposure or unusual access patterns tied to metadata credentials.

“Treat any unplanned metadata access or credential usage as a red flag, especially when it follows a pattern of crafted input processing.”

Developer and operator best practices

• Apply strict input validation and keep document processing runtimes minimal in scope. Avoid running Pandoc with elevated privileges, and prefer read-only volumes where possible.
• Use ephemeral credentials and rotate them frequently. Prefer short-lived tokens over long-lived secrets, and ensure logging does not inadvertently capture credentials.
• Regularly scan dependencies for known vulnerabilities and test patches in a staging environment before deploying to production pipelines.
• Educate teams about the risk surface introduced by trusted tools and untrusted input. Build defense-in-depth around CI/CD and content-rendering stages to minimize blast radius.

Mitigation requires a combined effort: promptly patching software, hardening the metadata service, and enforcing rigorous credential hygiene. CVE-2025-51591 highlights a persistent truth in cloud security: even trusted tools can become threats if their usage patterns grant attackers a path to credentials. With careful configuration and vigilant monitoring, you can substantially reduce the risk to AWS IMDS and EC2 IAM credentials while maintaining productive document workflows.