markdown2 is vulnerable to cross-site scripting

published 2018-01-18 8 y ago modified 2026-06-17 4 mo ago also GHSA-p6h9-gw49-rqm4 , PYSEC-2018-13 , EUVD-2018-0089

cvss: 6.1; version 3.0, NVD
cisa kev: Not listed; not in CISA's catalog
epss: 0.8%; EPSS 0.8% chance of exploitation in 30 days, percentile 57%
public exploits: 0; none known

An issue was discovered in markdown2 (aka python-markdown2) through 2.3.5. The safe_mode feature, which is supposed to sanitize user input against XSS, is flawed and does not escape the input properly. With a crafted payload, XSS can be triggered, as demonstrated by omitting the final '>' character from an IMG tag.

Patch / fix

fixed in 1 distros 1 links 2

pypi markdown2 2.3.6

python-markdown2 openSUSE Tumbleweed 2.5.5-1.3
python-markdown2 openSUSE Tumbleweed 2.4.13-1.2
python-markdown2 openSUSE Tumbleweed 2.4.0-2.4

opensuse advisories openSUSE-SU-2026:12016-1 openSUSE-SU-2024:14146-1 openSUSE-SU-2024:11237-1

github.com/trentm/python-markdown2@1b1dcdd commit
github.com/trentm/python-markdown2#303 pull request

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2018-5773 updated 2025-11-21 cvss 8.0

python-markdown2: Unsanitized input in markdown() method allows for cross-site scripting (XSS)

Red Hat All currently supported Red Hat products
not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

Exploit prediction

0.82% chance of exploitation in the next 30 days, higher than 57% of all scored CVEs (FIRST EPSS, 2026-11-09).

CVSS scores

assigned by	version	score	vector
NVD	3.0	6.1	CVSS:3.0/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
NVD	2.0	4.3	AV:N/AC:M/Au:N/C:N/I:P/A:N
GitHub	3.0	6.1	CVSS:3.0/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

Affected packages

ecosystem	package	affected	fixed in
pypi	markdown2	<2.3.6	2.3.6

Classification

Weakness

CWE-79 Improper Neutralization of Input During Web Page Generation

References

github.com /trentm/python-markdown2/pull/303
web
github.com /trentm/python-markdown2/commit/1b1dcdd727c0ef03453b9f5ef5ae3679f1d72323
web
github.com /trentm/python-markdown2/issues/285
web, third-party-advisory, report
nvd.nist.gov /vuln/detail/CVE-2018-5773
advisory
github.com /google/osv/issues/430
web
github.com /advisories/GHSA-p6h9-gw49-rqm4
advisory
github.com /pypa/advisory-database/tree/main/vulns/markdown2/PYSEC-2018-13.yaml
web
github.com /trentm/python-markdown2
package
github.com /trentm/python-markdown2/blob/master/CHANGES.md#python-markdown2-236
web

Sources

Fencer Intel keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

Summary