CVE-2025-54869 is a medium-severity Denial of Service (DoS) vulnerability affecting versions of the Setasign FPDI PHP library prior to 2.6.3. FPDI is widely used to read and import pages from existing PDF documents into new PDFs, often serving as a template mechanism in conjunction with FPDF. The vulnerability arises from improper resource allocation controls (CWE-770) when processing user-supplied PDF files. Specifically, an attacker can craft a malicious PDF file that triggers excessive memory consumption during processing, leading to server-side script crashes due to memory exhaustion. This flaw does not require user interaction but does require at least limited privileges (low privileges) to upload or submit PDF files to the vulnerable application. The vulnerability does not impact confidentiality or integrity directly but severely impacts availability by causing service outages. The CVSS 4.0 vector (AV:N/AC:L/AT:P/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N) reflects a network attack vector with low attack complexity, requiring privileges but no user interaction, and resulting in high availability impact. No known exploits are currently in the wild, and the issue was publicly disclosed in August 2025. The vulnerability is remediated by upgrading FPDI to version 2.6.3 or later, which includes proper resource throttling and limits to prevent memory exhaustion. Organizations using FPDI to process untrusted PDF inputs should prioritize patching to avoid potential DoS attacks that could disrupt service availability.

For European organizations, the primary impact of this vulnerability is service disruption due to Denial of Service attacks. Organizations that rely on FPDI for PDF processing in web applications, document management systems, or automated PDF workflows are at risk of having their services rendered unavailable by maliciously crafted PDFs. This can affect customer-facing portals, internal document processing, or any automated system ingesting user-supplied PDFs. The disruption could lead to operational downtime, loss of productivity, and potential reputational damage, especially for sectors with high document processing volumes such as finance, legal, government, and healthcare. Since the vulnerability requires low privileges but no user interaction, attackers could exploit it remotely if the application accepts PDF uploads from authenticated or semi-authenticated users. The absence of confidentiality or integrity impact limits the risk to data breaches, but the availability impact can be significant, particularly for critical services. European organizations with compliance obligations around service availability (e.g., under GDPR or sector-specific regulations) may face regulatory scrutiny if they fail to mitigate this vulnerability promptly.

1. Upgrade FPDI to version 2.6.3 or later immediately to apply the official fix that introduces resource allocation limits and throttling. 2. Implement strict input validation and sanitization on all PDF uploads to detect and block suspicious or malformed PDFs before processing. 3. Employ resource usage monitoring and limits at the application and server level, such as PHP memory limits and execution timeouts, to prevent excessive resource consumption from impacting overall service availability. 4. Use application-layer firewalls or web application firewalls (WAFs) with custom rules to detect and block abnormal PDF upload patterns or repeated requests from the same source. 5. Restrict PDF upload functionality to trusted users or implement multi-factor authentication to reduce the attack surface. 6. Maintain detailed logging and alerting on PDF processing failures and resource exhaustion events to enable rapid detection and response. 7. Consider isolating PDF processing in sandboxed environments or separate microservices to contain potential DoS impacts and prevent cascading failures in core systems.