CVE-2026-111758
Description
A flaw was found in markdown-it. A remote attacker can cause a Denial of Service (DoS) by providing specially crafted Markdown input that contains an unclosed link reference definition spanning multiple lines. Processing this input triggers excessive CPU consumption due to inefficient string handling, which can cause the application to hang and become unresponsive to other users.
Statement
This vulnerability is rated as Important severity because an unauthenticated remote attacker can exhaust server CPU resources without elevated privileges, leading to complete service disruption. In Red Hat environments, applications that process user-supplied Markdown content—such as Developer Hub and Dev Spaces—are vulnerable to event loop stalls when handling maliciously formatted documents. The flaw stems from quadratic parsing behavior on unclosed reference definitions, which allows relatively small multi-line payloads to consume significant processing time and render the shared service unresponsive.
Mitigation
--- CME Mitigation Guidance (2026-10-20) ---
Disclaimer: The following mitigation solutions are provided as a courtesy, pending the application of an official patch. This content was generated utilizing AI tools in conjunction with data from https://cmetaxonomy.org. Customers are advised to independently evaluate and test these temporary mitigations within their own infrastructure.
The highest-value action is to disable the markdown-it reference block rule or avoid lazy string concatenation during multi-line link reference parsing: upgrade to markdown-it 14.3.3 and 15.0.3 (or the fixed Libgit/Forgejo/Ansible/Libgit2/Nextcloud/Markdownlint Cli/Rhoai/Odh Workbench Codeserver Datascience Cpu Py312 Rhel/Rhdh/Rhdh Hub Rhel/Devspaces/Code Rhel/Devspaces/Openvsx Rhel/Devspaces/Pluginregistry Rhel/Thrift/Ansible Automation Platform/Automation Portal/Rhoai/Odh Feature Server Rhel/Rhdh/Red Hat Developer Hub Backstage Plugin Orchestrator Backend/Ansible Automation Platform/Bootc Automation Portal Rhel/Rh Podman Desktop/Rhdh/Red Hat Developer Hub Backstage Plugin Lightspeed Backend/Redhat User Workloads/Mintmaker Renovate Image builds), which scan the source string directly by index position and enforce a 999-character limit on reference labels instead of lazily concatenating continuation lines, closing all 2 injection vectors (crafted multi-line unclosed link reference label, crafted multi-line unclosed link reference title). Until patched, this is a concern on applications parsing untrusted user-supplied Markdown with the reference block rule enabled, so disable the reference rule via configuration or restrict untrusted user Markdown input parsing. As a compensating measure, set per-process CPU time limits via RLIMIT_CPU to bound excessive processing time from quadratic string flattening and apply rate limiting and connection throttling to restrict repeated parsing requests. These controls limit blast radius and contain exploitation, but they do not fix the underlying quadratic cons-string flattening defect — apply the upstream patch to fully remediate.
Highest-impact CME: CME-1316 Algorithmic Complexity Safeguards (Pattern/Regex Execution Limits) (high)
Common Vulnerability Scoring System (CVSS) Score Details
Info alert:Important note
CVSS scores for open source components depend on vendor-specific factors (e.g. version or build chain). Therefore, Red Hat's score and impact rating can be different from NVD and other vendors. Red Hat remains the authoritative CVE Naming Authority (CNA) source for its products and services (see Red Hat classifications).
The following CVSS metrics and score provided are preliminary and subject to review.
CVSS v3 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 7.5 | N/A | 7.5 |
| Attack Vector | Network | N/A | Network |
| Attack Complexity | Low | N/A | Low |
| Privileges Required | None | N/A | None |
| User Interaction | None | N/A | None |
| Scope | Unchanged | N/A | Unchanged |
| Confidentiality | None | N/A | None |
| Integrity Impact | None | N/A | None |
| Availability Impact | High | N/A | High |
Vector
Red Hat: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
cve.org: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
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