8.7

CVE-2026-115352: Mistune before 3.3.0 Quadratic-Time DoS via Unmatched Brackets in Inline Parser

Deferred
AliasesDEBIAN-CVE-2026-115352UBUNTU-CVE-2026-115352
Published 22-10-2026Last modified 23-10-2026

Vulnerability summary

CVE-2026-115352 is a high (CVSS 8.7) Inefficient Algorithmic Complexity vulnerability in lepture mistune. EPSS estimates a 0.44% chance of exploitation in the next 30 days, higher than 38.1% 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
0.44%
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. 23-10-2026
    Last modifiedVulnerability information updated.

Description

Mistune before 3.3.0 contains an algorithmic complexity vulnerability in the inline link parser that allows unauthenticated attackers to exhaust CPU by submitting long runs of unmatched '[' characters. Attackers can send small markdown payloads that trigger O(N^2) parse_link_text and parse_link_label probing, occupying rendering workers for 30+ seconds per 16 KB input.

CVSS metrics

7 scores · 4 sources · 2 versions

EPSS trend

Probability

0.44%

Chance of exploitation in the next 30 days

Percentile

38%

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, no 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