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Response snapshot Oct 26, 2026, 23:55 UTC

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VulnerabilityCVE-2026-115355

Mistune: Path Traversal and XSS in Include directive

The Include directive in `src/mistune/directives/include.py` does not validate that the resolved file path stays within the source directory, allowing path traversal via `../` sequences to read arbitrary files.

At a glance

Exploited
Not known
Severity
8.7 High (CVSS 4.0)
Chance of exploitation
0.5% in the next 30 days
Sources
2 independent sources

What to do

GitHub lists first patched versions: mistune: 3.3.0. Confirm the affected range and upgrade guidance in the exact advisory.

Read GitHub-reviewed advisory GHSA-h7ww-273w-6cm8 (opens a new tab)

What happened

The Include directive in `src/mistune/directives/include.py` does not validate that the resolved file path stays within the source directory, allowing path traversal via `../` sequences to read arbitrary files.

Additionally, error messages and included file contents are rendered without HTML escaping, leading to XSS even when `escape=True`.

Affected functions: - Path resolution (lines 27-31) - `block_error()` in html.py (line 140) - `render_html_include()` (line 72)

The Include plugin must be explicitly enabled via the plugins parameter.

Continue reading

Affected package ranges reported by GitHub: mistune: <= 3.2.0

Scores and how they were measured

CVSS base severity

8.7

Version 4.0As of

CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

Measurement source (opens a new tab)

How bad it is if exploited. Not a prediction of exploitation or proof you are exposed.

EPSS probability

0.5%

Scored Percentile 39.7%

Model and measurement source (opens a new tab)

A model's estimate of exploitation in the next 30 days, not certainty or your own risk.

Related technology

Sources

  1. Primary source

    GitHub-reviewed advisory GHSA-h7ww-273w-6cm8 (opens a new tab)

    The public advisory supplies the description, affected package/version ranges, and any listed CVSS metric. GitHub review is not local review.

    Published Checked

  2. Primary source

    GitHub public advisory API page (opens a new tab)

    The API page supplied GHSA-h7ww-273w-6cm8, its actual identifiers, source dates, and structured metrics.

    Published Date not suppliedChecked

  3. Primary source

    GitHub public advisory API page (opens a new tab)

    The API page supplied GHSA-h7ww-273w-6cm8, its actual identifiers, source dates, and structured metrics.

    Published Date not suppliedChecked

  4. Primary source

    GitHub public advisory API page (opens a new tab)

    The API page supplied GHSA-h7ww-273w-6cm8, its actual identifiers, source dates, and structured metrics.

    Published Date not suppliedChecked

  5. Primary source

    GitHub public advisory API page (opens a new tab)

    The API page supplied GHSA-h7ww-273w-6cm8, its actual identifiers, source dates, and structured metrics.

    Published Date not suppliedChecked

  6. Primary source

    NVD CVE-2026-115355 (opens a new tab)

    NVD record: description, CVSS (the CNA score is preferred), affected products, and publication date. Not evidence of exploitation.

    Published Checked

  7. Primary source

    NVD CVE API 2.0 (opens a new tab)

    The NVD API page that supplied this CVE record.

    Published Date not suppliedChecked

  8. Primary source

    FIRST measured EPSS score (opens a new tab)

    Measured EPSS probability and percentile for CVE-2026-115355, scored 2026-10-26. This is a model estimate, not proof of exposure.

    Published Checked

Cite this record

For factual claims, cite the primary sources above; cite KEVWire for its compilation, dates, and classifications.

APA

KEVWire. (2026, October 23). Mistune: Path Traversal and XSS in Include directive (CVE-2026-115355). https://kevwire.com/record/CVE-2026-115355

MLA

"Mistune: Path Traversal and XSS in Include directive (CVE-2026-115355)." KEVWire, 23 Oct. 2026, kevwire.com/record/CVE-2026-115355.

Chicago

KEVWire. "Mistune: Path Traversal and XSS in Include directive (CVE-2026-115355)." Last modified October 23, 2026. https://kevwire.com/record/CVE-2026-115355.

Evidence summary (plain text)

Mistune: Path Traversal and XSS in Include directive (Oct 23, 2026).
The Include directive in `src/mistune/directives/include.py` does not validate that the resolved file path stays within the source directory, allowing path traversal via `../` sequences to read arbitrary files.

Additionally, error messages and included file contents are rendered without HTML escaping, leading to XSS even when `escape=True`.
CVSS 8.7 (version 4.0; evidence as of Oct 22, 2026; https://nvd.nist.gov/vuln/detail/CVE-2026-115355).
EPSS 0.5% for the following 30 days, scored Oct 26, 2026 (https://api.first.org/data/v1/epss?cve=CVE-2026-115355&date=2026-10-26).
Sources:
GitHub-reviewed advisory GHSA-h7ww-273w-6cm8: https://github.com/advisories/GHSA-h7ww-273w-6cm8
GitHub public advisory API page: https://api.github.com/advisories?type=reviewed&per_page=100&sort=updated&direction=desc&after=Y3Vyc29yOnYyOpK0MjAyNi0xMC0yM1QyMDo1MTozMFrOAAf0Mg%3D%3D
GitHub public advisory API page: https://api.github.com/advisories?type=reviewed&per_page=100&sort=updated&direction=desc&after=Y3Vyc29yOnYyOpK0MjAyNi0xMC0yM1QyMDo0OToxMlrOAAf0LQ%3D%3D
GitHub public advisory API page: https://api.github.com/advisories?type=reviewed&per_page=100&sort=updated&direction=desc&after=Y3Vyc29yOnYyOpK0MjAyNi0xMC0yM1QyMDo0NzoxN1rOAAf0Kg%3D%3D
GitHub public advisory API page: https://api.github.com/advisories?type=reviewed&per_page=100&sort=updated&direction=desc
NVD CVE-2026-115355: https://nvd.nist.gov/vuln/detail/CVE-2026-115355
NVD CVE API 2.0: https://services.nvd.nist.gov/rest/json/cves/2.0?pubStartDate=2026-10-12T13:35:55.142Z&pubEndDate=2026-10-26T13:35:55.142Z&resultsPerPage=500&startIndex=8500
FIRST measured EPSS score: https://api.first.org/data/v1/epss?cve=CVE-2026-115355&date=2026-10-26
Record ID: CVE-2026-115355.
Record origin: Ingested record.
AI evidence: Not assessed.
Known exploitation: Not assessed.
Zero-day status: Not assessed. KEV membership alone does not establish zero-day status.
About this data

This record was ingested from a data source. Retrieved: Oct 26, 2026, 19:40 UTC. Ingestion is not an independent editorial investigation.

A CISA KEV listing documents known exploitation, not necessarily a zero-day; absence from the catalog does not prove a vulnerability has never been exploited.

Technology tags indicate possible relevance, not verified exposure. Confirm the affected product, version, and configuration against your own inventory; KEVWire does not scan your systems.

A personal reading checklist on this device, not verified remediation.

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Record details

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