8.7

CVE-2019-25781: Python-Markdown 3.0 through 3.11.2 Denial of Service via Link Bracket Parsing

Awaiting analysis
AliasesUBUNTU-CVE-2019-25781DEBIAN-CVE-2019-25781
Published 29-10-2026Last modified 03-11-2026

Vulnerability summary

CVE-2019-25781 is a high (CVSS 8.7) Inefficient Algorithmic Complexity vulnerability in python-markdown markdown. EPSS estimates a 0.42% chance of exploitation in the next 30 days, higher than 36.5% of scored vulnerabilities.

Priority
Prioritisesevere

Severe, CVSS 8.7 (CVE.org); no exploitation reported by the 5 checked sources; EPSS 0% (FIRST, 03-11-2026)

Source freshness unavailable

How is this decided?
CVSS score
8.7/10
010
High · v4.0 (CVE.org)
EPSS score
0.42%
0%100%
Low · Change unavailable
KEVNot listedNot listed by any tracked catalog.
RansomwareNot flaggedNo ransomware use recorded.
Public exploits0No public exploits recorded

Timeline

  1. 29-10-2026
    PublishedVulnerability first disclosed.
  2. 03-11-2026
    Last modifiedVulnerability information updated.

Description

Python-Markdown 3.0 through 3.11.2 contains an algorithmic complexity vulnerability in inline link parsing that allows remote attackers to exhaust CPU through unmatched brackets. Attackers can submit short Markdown containing repeated [ or ![ characters, forcing LinkInlineProcessor.getText() and getLink() into quadratic scans that keep workers busy for minutes.

CVSS metrics

7 scores · 4 sources · 2 versions

EPSS trend

Probability

0.42%

Chance of exploitation in the next 30 days

Percentile

37%

Versus all other CVEs

30-day change

Change unavailable

Change unavailable

30-10-202603-11-2026

Known exploited

Compare KEV catalogs
CISA KEV

Not in the CISA KEV catalog.

ENISA CNW

Not in the ENISA CNW catalog.

CIRCL

Not in the CIRCL catalog.

Public exploits

0 found

No public exploits indexed.

Weaknesses

CWE · root cause

Affected systems

Version check

Known conditions: network-reachable, no authentication, no user interaction (CVSS vector). Other conditions: not stated in public data.

Debian1 product
  • python-markdownAll versions (No fix recorded)
Python-markdown1 product
Ubuntu1 product
  • python-markdownAll versions (No fix recorded)

3 vendors · 3 products

References

8 links