CVE-2026-1285 is a denial-of-service vulnerability rooted in inefficient algorithmic complexity (CWE-407) within the Django web framework's HTML truncation utilities. The affected functions, django.utils.text.Truncator.chars() and Truncator.words(), when invoked with html=True, attempt to truncate HTML content safely by counting characters or words while preserving HTML structure. However, if the input contains a large number of unmatched HTML end tags, the algorithm's complexity increases dramatically, causing excessive CPU and memory consumption. This behavior can be triggered remotely by submitting crafted HTML inputs to web applications that utilize these truncation methods or the related template filters truncatechars_html and truncatewords_html. The vulnerability affects Django versions 6.0 before 6.0.2, 5.2 before 5.2.11, and 4.2 before 4.2.28, with earlier unsupported versions possibly vulnerable as well. Exploitation does not require authentication or user interaction beyond submitting malicious input, making it a straightforward vector for denial-of-service attacks. Although no public exploits have been reported, the vulnerability poses a risk to any Django-based web application that processes untrusted HTML content and uses these truncation features. The issue was responsibly disclosed by Seokchan Yoon and is documented without an assigned CVSS score as of publication.

For European organizations, this vulnerability presents a risk of denial-of-service attacks that can degrade or disrupt web services built on affected Django versions. Organizations running public-facing web applications that accept or process user-generated HTML content and use the vulnerable truncation methods are particularly at risk. Such DoS attacks can lead to service downtime, impacting business continuity, customer trust, and potentially causing financial losses. The impact is heightened for sectors relying heavily on web applications, including e-commerce, government portals, media, and online services. Additionally, the vulnerability could be exploited as part of a larger attack chain to distract or overwhelm security teams. Given the widespread use of Django in Europe, especially in countries with strong software development ecosystems, the threat could affect a broad range of organizations. However, the lack of known exploits in the wild suggests that immediate widespread impact is limited but could increase if weaponized.

The primary mitigation is to upgrade Django installations to the fixed versions: 6.0.2 or later, 5.2.11 or later, and 4.2.28 or later. Organizations should prioritize patching environments where untrusted HTML input is processed using the Truncator.chars() or Truncator.words() methods with html=True or the related template filters. Where immediate upgrading is not feasible, implement input validation to detect and reject HTML inputs with excessive unmatched end tags or suspiciously malformed HTML structures. Additionally, apply rate limiting and request throttling on endpoints that process such inputs to reduce the risk of resource exhaustion. Monitoring application performance and logs for unusual spikes in CPU or memory usage related to HTML processing can help detect exploitation attempts. Developers should review codebases for direct or indirect use of the vulnerable truncation methods and consider alternative safe truncation approaches or sanitization libraries. Finally, ensure that web application firewalls (WAFs) are configured to detect and block malformed HTML payloads that could trigger this vulnerability.