CVE-2026-59922— Mistune plugins/formatting: quadratic-time parsing on long runs of `~~x~~`, `==x==`, and `^^x^^` markers (strikethrough / mark / insert)
Quick assessment
Affected
lepture mistune
Exploitation
Public or AI PoC available; prioritize validation
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.
Hsiaoming Yang mistune是日本Hsiaoming Yang个人开发者的一个快速、可扩展的Markdown解析器。 Hsiaoming Yang mistune 3.3.0之前版本存在资源管理错误漏洞，该漏洞源于使用波浪号、等号或插入符号标记对时，在src/mistune/plugins/formatting.py中引发二次复杂度操作，导致通过CPU耗尽实现拒绝服务。
Possible ATT&CK Techniques 1 AI
T1496 · Resource Hijacking
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I. Basic Information for CVE-2026-59922
Vulnerability Information
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Vulnerability Title
Mistune plugins/formatting: quadratic-time parsing on long runs of `~~x~~`, `==x==`, and `^^x^^` markers (strikethrough / mark / insert)
Source: CVE Program / CVE List V5
Vulnerability Description
Mistune is a Python Markdown parser with renderers and plugins. Prior to 3.3.0, a run of closed tilde, equals-sign, or caret marker pairs around a character causes quadratic work in src/mistune/plugins/formatting.py when the strikethrough, mark, or insert plugin scans for matching markers from each possible start position, allowing denial of service through CPU exhaustion. This issue is fixed in version 3.3.0.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Source: CVE Program / CVE List V5
Vulnerability Type
算法复杂性
Source: CVE Program / CVE List V5
Vulnerability Title
Hsiaoming Yang mistune 资源管理错误漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Hsiaoming Yang mistune是日本Hsiaoming Yang个人开发者的一个快速、可扩展的Markdown解析器。 Hsiaoming Yang mistune 3.3.0之前版本存在资源管理错误漏洞，该漏洞源于使用波浪号、等号或插入符号标记对时，在src/mistune/plugins/formatting.py中引发二次复杂度操作，导致通过CPU耗尽实现拒绝服务。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)
Affected Products
II. Public POCs for CVE-2026-59922
| # | POC Description | Source Link | Shenlong Link |
|---|
AI-Generated POC
Verified env
Premium
Qwen3.6-35B-A3B
· 10990 chars
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III. Intelligence Information for CVE-2026-59922
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Patches & Fixes for CVE-2026-59922 (1)
Vendor Advisories for CVE-2026-59922 (1)
Vendor Pages for CVE-2026-59922 (1)
Same Patch Batch · lepture · 2026-07-08 · 9 CVEs total
| CVE-2026-59925 | 7.5 HIGH | inline_parser: quadratic-time parsing on long runs of `**x**` and `***x***` emphasis pairs |
| CVE-2026-59928 | 7.5 HIGH | Mistune block_parser: quadratic-time parsing on long lists of repeated reference-link defi |
| CVE-2026-59923 | 6.1 MEDIUM | Mistune: XSS via percent-encoded javascript URI bypass in safe_url() |
| CVE-2026-59929 | 6.1 MEDIUM | Mistune renderers/html.safe_url: HARMFUL_PROTOCOLS list misses legacy and chained schemes |
| CVE-2026-59924 | 5.9 MEDIUM | Mistune: Arbitrary File Read via Include directive path traversal |
| CVE-2026-59927 | 5.3 MEDIUM | Mistune directives/include: mutual `.. include::` recursion crashes the renderer with `Rec |
| CVE-2026-59930 | 4.3 MEDIUM | Mistune toc / TableOfContents directive: heading IDs use predictable `toc_N` numbering wit |
| CVE-2026-59926 | Mistune: XSS via unescaped class option in Admonition directive |
IV. Related Vulnerabilities
Same product: mistune
-
CVE-2026-76098
Mistune has Denial of Service — RecursionError via Excessive -
CVE-2026-59927
Mistune directives/include: mutual `.. include::` recursion -
CVE-2026-59928
Mistune block_parser: quadratic-time parsing on long lists o -
CVE-2026-59924
Mistune: Arbitrary File Read via Include directive path trav -
CVE-2026-59929
Mistune renderers/html.safe_url: HARMFUL_PROTOCOLS list miss
Same vendor: lepture
-
CVE-2026-76098
Mistune has Denial of Service — RecursionError via Excessive -
CVE-2026-59927
Mistune directives/include: mutual `.. include::` recursion -
CVE-2026-59928
Mistune block_parser: quadratic-time parsing on long lists o -
CVE-2026-59924
Mistune: Arbitrary File Read via Include directive path trav -
CVE-2026-59929
Mistune renderers/html.safe_url: HARMFUL_PROTOCOLS list miss
Same weakness: CWE-407
-
CVE-2026-110755
Text::CSV_XS versions before 1.65 for Perl allow quadratic C -
CVE-2026-101021
J4Care dcm4che Inefficient Algorithmic Complexity -
CVE-2026-110270
OW2 ASM 3.0 before 9.11 Exponential Memory Allocation in JSR -
CVE-2026-110261
OW2 ASM 3.0 before 9.11 Excessive CPU Consumption via ClassW -
CVE-2026-110260
OW2 ASM 3.0 before 9.11 Quadratic Memory Allocation via Exce
V. Comments for CVE-2026-59922
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