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CVE-2026-115349high8.7

Mistune 3.0.0 before 3.3.0 Denial of Service via Nested Bracket Parsing

Impact

Mistune versions 3.0.0 before 3.3.0 contain a denial of service vulnerability due to inefficient parsing of nested brackets, allowing attackers to exhaust server CPU with crafted requests. The vulnerability is in the parse_link_text function. Attackers can submit markdown with deeply nested square brackets, triggering quadratic parsing time.

Summarized by @cf/meta/llama-3.3-70b-instruct-fp8-fast. Verify details against the original sources.

Affected packages

This source has no supported package-version data for matching. You can read the advisory here, but this record alone cannot power a dependency check.

Affected products

Vendor version evidence. Product records are separate from automatic dependency matching.

lepture · VulnCheck

mistune

2 ranges
VulnCheck version evidence

Package identity

pkg:pypi/mistuneExplore mistune →

Identity supplied by VulnCheck. Version matching requires compatible range evidence.

Compare with this publisher’s ranges. This does not inspect your installation.

affected

3.0.0 → before 3.3.0

semver versions

unaffected

3.3.0

semver versions

unknown

Other versions: unaffected

Original source description

Mistune from 3.0.0 before 3.3.0 contains an algorithmic complexity denial of service vulnerability in the parse_link_text function in src/mistune/helpers.py. Attackers can submit markdown with deeply nested square brackets triggering quadratic parsing time, exhausting server CPU with small crafted requests.

Inside the record

Evidence available

Package identity
Version evidence
Remediation guidance · not supplied
Weakness classification
Additional publishers

Describes the evidence in this view, not whether the product is safe.

Original records

CVE-2026-115349

View the latest unmodified CVE JSON from the official source. It may be newer than this imported page.

cve.new JSON →

Underlying weaknesses

The source’s classification of what caused the vulnerability.

CWE-1333 ↗

Inefficient Regular Expression Complexity

VulnCheck

Related →

Environment requirements

These conditions apply together as specified by the publisher. A matching product name alone does not establish exposure.

VulnCheck · platform conditions

Any condition may hold

Vulnerable product

cpe:2.3:a:mistune_project:mistune:*:*:*:*:*:*:*:*

From (inclusive): 3.0.0

Before: 3.3.0

Original applicability statements
[
  {
    "nodes": [
      {
        "operator": "OR",
        "negate": false,
        "cpeMatch": [
          {
            "vulnerable": true,
            "criteria": "cpe:2.3:a:mistune_project:mistune:*:*:*:*:*:*:*:*",
            "versionStartIncluding": "3.0.0",
            "versionEndExcluding": "3.3.0"
          }
        ]
      }
    ]
  }
]
Contributing organizations · 2
VulnCheck

Assigning organization

2026-10-22
CISA-ADP

Additional data publisher

2026-10-26

What changed

Follow changes
No substantive changes have been recorded here yet. History starts when cve.new observes a change after tracking is enabled; earlier edits are not reconstructed.

Large field values are marked as truncated previews. Original source snapshots remain retained.

References

2 sources
github.com/lepture/mistune/security/advisories/GHSA-3q64-rw38-243v
vendor-advisoryVulnCheck
www.vulncheck.com/advisories/mistune-3.0.0-before-3.3.0-denial-of-service-via-nested-bracket-parsing
third-party-advisoryVulnCheck