CVE-2026-68538: fulgur: Unbounded counters() expansion in generated content causes memory/CPU exhaustion (denial of service)
fulgur converts untrusted HTML/CSS into PDF, commonly on a server that processes input supplied by many tenants. From version 0.15.0 to before version 0.27.0, resolving the CSS counters(name, sep) function in generated content was bounded neither in the size of a single expansion nor in the aggregate work across an element tree. An attacker able to submit HTML/CSS to a fulgur-based conversion service can trigger CPU and memory exhaustion with a trivially small payload, denying service to the host and any co-tenants. This issue has been patched in version 0.27.0.
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
fulgurto a version that resolves this vulnerability.Fixed in 0.27.0
Event History
Frequently Asked Questions
Which deployments are exposed to this issue?
Deployments using fulgur versions 0.15.0 through versions before 0.27.0 are affected when they convert attacker-controlled or otherwise untrusted HTML/CSS to PDF. Server-side multi-tenant conversion services are specifically at risk because exhaustion can affect the host and co-tenants.
What does an attacker need to exploit it?
An attacker only needs to submit HTML/CSS that is processed by a vulnerable fulgur-based conversion service. No authentication, user interaction, or complex payload is required according to the supplied severity vector and description.
What is the impact of successful exploitation?
A small crafted payload can cause unbounded CPU and memory consumption while resolving CSS counters(name, sep) in generated content. This can deny PDF conversion service to the host and other tenants sharing it.
What version fixes the issue?
The issue is patched in fulgur version 0.27.0. Upgrade affected installations to version 0.27.0 or later.