Mistune is a Python Markdown parser with renderers and plugins. Prior to 3.3.0, a Markdown document containing many repeated or distinct reference-link definitions causes quadratic work in src/mistune/blockparser.py and the reflinks environment dictionary handling, allowing denial of service through CPU exhaustion. This issue is fixed in version 3.3.0.
{
"cna_assigner": "GitHub_M",
"cwe_ids": [
"CWE-1333",
"CWE-407"
],
"osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/59xxx/CVE-2026-59928.json"
}{
"source": [
"CPE_RANGE",
"REFERENCES"
],
"extracted_events": [
{
"introduced": "0"
},
{
"fixed": "3.3.0"
}
],
"cpe": "cpe:2.3:a:mistune_project:mistune:*:*:*:*:*:*:*:*"
}