5.3

CVE-2026-115351: Mistune 3.2.1 before 3.3.0 CSS Injection via Figure Directive figwidth Option

Deferred
AliasesDEBIAN-CVE-2026-115351UBUNTU-CVE-2026-115351
Published 22-10-2026Last modified 29-10-2026

Vulnerability summary

CVE-2026-115351 is a medium (CVSS 5.3) Improper Control of Generation of Code vulnerability in lepture mistune. EPSS estimates a 0.22% chance of exploitation in the next 30 days, higher than 12.7% of scored vulnerabilities.

Priority
Routine

Not severe (CVSS 5.3, network access); no exploitation reported by the 5 checked sources

Source freshness unavailable

How is this decided?
CVSS score
5.3/10
010
Medium · v4.0 (CVE.org)
EPSS score
0.22%
0%100%
Low · Change unavailable
KEVNot listedNot listed by any tracked catalog.
RansomwareNot flaggedNo ransomware use recorded.
Public exploits0No public exploits recorded

Timeline

  1. 22-10-2026
    PublishedVulnerability first disclosed.
  2. 29-10-2026
    Last modifiedVulnerability information updated.

Description

Mistune from 3.2.1 before 3.3.0 contains a CSS injection vulnerability that allows attackers controlling markdown input to inject arbitrary style declarations via the unvalidated figwidth option of the figure directive. Attackers can append declarations like background:url() to the rendered figure style attribute, forcing victim browsers to send requests to attacker servers and leak attribute values.

CVSS metrics

7 scores · 4 sources · 2 versions

EPSS trend

Probability

0.22%

Chance of exploitation in the next 30 days

Percentile

13%

Versus all other CVEs

30-day change

Change unavailable

Change unavailable

23-10-202603-11-2026

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, user interaction (CVSS vector). Other conditions: not stated in public data.

Debian1 product
  • mistuneAll versions (No fix recorded)
Lepture1 product
Ubuntu1 product
  • mistuneAll versions (No fix recorded)

3 vendors · 3 products

References

5 links