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A high-severity denial-of-service vulnerability, tracked as CVE-2026-49851, was disclosed in the Python Markdown parser Mistune. The flaw affects versions prior to 3.3.0 and allows attacker-controlled Markdown input to trigger excessive CPU consumption through quadratic-time parsing in parse_link_text. Inputs containing long runs of consecutive [ characters can force repeated regex scans, causing parsing time to grow superlinearly and making the issue remotely exploitable in applications that process untrusted Markdown.
The bug stems from an interaction in mistune/inline_parser.py where InlineParser.parse() advances one character at a time after parse_link() fails, while parse_link_text() rescans for a closing bracket on each attempt. A published proof of concept showed a 6,400-character payload increasing processing time to about 3.19 seconds, creating practical denial-of-service risk for web applications, APIs, and documentation platforms. Advisories classify the issue as CWE-400: Uncontrolled Resource Consumption and recommend upgrading to Mistune 3.3.0 or later; a proposed code-level fix is to return the furthest scanned position even on parse failure so the outer loop can skip ahead.
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CVE-2026-49851 was published for a high-severity denial-of-service vulnerability affecting Mistune versions prior to 3.3.0. The CVE entry states the issue is remotely exploitable via attacker-controlled Markdown input and recommends upgrading to Mistune 3.3.0 or later.
A GitHub security advisory disclosed a CPU exhaustion denial-of-service issue in Mistune caused by approximately O(n²) behavior in parse_link_text when parsing Markdown containing many consecutive "[" characters. The advisory described the root cause, provided a proof of concept and benchmark, and suggested changing parsing behavior to skip ahead after failed link parsing.
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A critical vulnerability (CVE-2025-65108, CVSS 10.0) has been identified in the `md-to-pdf` tool, which is used to convert Markdown files to PDF using Node.js and headless Chrome. The flaw allows attackers to achieve remote code execution by injecting malicious JavaScript into the front-matter section of Markdown files, exploiting the way the gray-matter library parses these blocks. This vulnerability is remotely exploitable and poses a significant risk to any system processing untrusted Markdown files with affected versions of `md-to-pdf`. The issue has been addressed in version 5.2.5 of the `md-to-pdf` library, and users are strongly advised to update to this version to mitigate the risk. No specific affected product versions are listed, but the vulnerability impacts all prior versions that use the vulnerable parsing mechanism. Security advisories have been published to highlight the severity and exploitation potential of this flaw, emphasizing the need for immediate remediation in environments where Markdown-to-PDF conversion is automated or exposed to user-supplied content.
Jun 29, 2026
Warp disclosed and patched **CVE-2026-48704** / **GHSA-589x-4mxh-jcrf**, a high-severity flaw in its Markdown notebook link handling that could cause executable local files to be opened through the operating system’s default file handler. The bug affects Warp versions from `0.2023.10.24.08.03.stable_00` up to, but not including, `0.2026.05.06.15.42.stable_01`, and could be triggered when a user clicked a malicious local-file link embedded in attacker-controlled Markdown content or a project. Successful exploitation could lead to code execution with the privileges of the Warp user, with confirmed impact on **macOS** and **Windows** and conditional impact on **Linux** depending on desktop environment and file-handler settings. Warp fixed the issue in version `0.2026.05.06.15.42.stable_01` by changing unsafe local-link behavior so files are revealed in the file manager instead of opened, and urged users to update immediately or avoid opening untrusted Markdown files and clicking embedded links until patched.
Jun 29, 2026
Python disclosed **CVE-2026-15308**, a high-severity denial-of-service flaw in `html.parser.HTMLParser` that can drive CPU exhaustion when applications incrementally parse untrusted HTML containing repeated unterminated markup declarations. The bug stems from quadratic-time behavior in `feed()`, where small repeated chunks force expensive rescanning and buffer concatenation across malformed tags, comments, doctypes, CDATA sections, processing instructions, and RAWTEXT elements. CPython maintainers shipped fixes and backports across supported branches including 3.10 through 3.15, with commits updating buffering logic to accumulate pending input more efficiently, defer reparsing until enough data arrives, adapt parsing thresholds based on parser progress, and flush buffered data on `close()`. The Python Software Foundation also updated the CVE record to clarify that affected versions are **earlier than 3.15.0**, not earlier than 3.16.0, while published metadata classifies the issue as **CWE-400** and notes no known exploitation at the time of disclosure.
Jul 10, 2026