CVE-2017-15612 Cross-site Scripting in Mistune
An attacker can execute arbitrary scripts in a victim's browser by crafting malicious Markdown input processed by the Mistune library.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- A user has to click or open something
- Fix
- Available
What is CVE-2017-15612?
CVE-2017-15612 is a medium-severity cross-site scripting vulnerability in n/a, published on 19 Oct 2017. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Official description
mistune.py in Mistune 0.7.4 allows XSS via an unexpected newline (such as in java\nscript:) or a crafted email address, related to the escape and autolink functions.
Weakness: CWE-79
Which versions are affected by CVE-2017-15612?
3 open source packages ship an affected version, including mistune. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
mistune PyPI | All versions | 0.8 |
mistune PyPI | All versions | 0.8 |
mistune PyPI | All versions | 0.8 |
Products include Mistune Project Mistune.
How do I fix CVE-2017-15612?
Upgrade mistune to 0.8 or later.
Escape output for the context it lands in and set a strict Content Security Policy. Upgrading the affected component is the real fix. More about Cross-site scripting.
Is CVE-2017-15612 being exploited?
There is no known exploitation of CVE-2017-15612 in the wild and no public exploit code.
Other vulnerabilities in n/a
- CVE-2026-59922 Mistune plugins/formatting: quadratic-time parsing on long runs of `~~x~~`, `==x==`, and `^^x^^` markers (strikethrough / mark / insert)
- CVE-2026-59925 inline_parser: quadratic-time parsing on long runs of `**x**` and `***x***` emphasis pairs
- CVE-2026-59928 Mistune block_parser: quadratic-time parsing on long lists of repeated reference-link definitions
- CVE-2026-59923 Mistune: XSS via percent-encoded javascript URI bypass in safe_url()
- CVE-2026-59929 Mistune renderers/html.safe_url: HARMFUL_PROTOCOLS list misses legacy and chained schemes that historically chain to `javascript:` execution
Sources
Also known as DEBIAN-CVE-2017-15612, GHSA-hpv5-v8g5-c864, PYSEC-2017-80, UBUNTU-CVE-2017-15612.