A Regular-Expression Denial of Service (ReDoS) in the Markdown2.

published 2026-10-15 25 d ago modified 2026-10-20 20 d ago also EUVD-2026-102186

cvss: 7.5; version 3.1, CNA
cisa kev: Not listed; not in CISA's catalog
epss: 0.4%; EPSS 0.4% chance of exploitation in 30 days, percentile 33%
public exploits: 0; none known

A Regular-Expression Denial of Service (ReDoS) in the Markdown2. extract_metadata() function (lib/markdown2.py) of trentm markdown2 through v2.5.5 allows attackers to cause a Denial of Service (DoS) via a crafted Markdown document.

Patch / fix

distros 1

python-markdown2 openSUSE Tumbleweed 2.5.5-2.1

opensuse advisories openSUSE-SU-2026:12159-1

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-2026-88753 updated 2026-10-20 cvss 5.3

markdown2: markdown2: Denial of Service via crafted Markdown document

Red Hat OpenShift Container Platform 4 openshift4/ose-olm-catalogd-rhel9
affected: workaround, no fix available “Fix deferred”

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

CISA SSVC

Exploitation: Proof of concept is public
Automatable: yes
Technical impact: partial
Assessed: 20 d ago (2026-10-20)

Exploit prediction

0.39% chance of exploitation in the next 30 days, higher than 33% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

gist.github.com https://gist.github.com/NanaSec/354b4188bbd7f4105008c7b8be49b0ba referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by	version	score	vector
CISA ADP	3.1	7.5	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
CNA	3.1	7.5	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Classification

Weakness

CWE-400 Uncontrolled Resource Consumption

References

gist.github.com /NanaSec/354b4188bbd7f4105008c7b8be49b0ba
exploit

Sources

CVE List CVE-2026-88753
NVD CVE-2026-88753

Fencer Vulns 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