CVE-2025-46656Public exploit

Memory exhaustion via unbounded heading prefix generation

Published Apr 26, 2025 · Updated Apr 29, 2025

Denial of service in Matthew Tretter Markdownify before 0.14.1 allows local users to exhaust memory via oversized HTML heading levels. The convert_hn method treats the numeric suffix of any h-prefixed tag as a heading level and repeats the Markdown hash character that many times without bounding it. The path requires an application to process attacker-controlled HTML; resource exhaustion raises MemoryError or freezes the host.

CVSS severity2.9
Low
EPSS probability0.21%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Denial of service in Matthew Tretter Markdownify before 0.14.1 allows local users to exhaust memory via oversized HTML heading levels. The convert_hn method treats the numeric suffix of any h-prefixed tag as a heading level and repeats the Markdown hash character that many times without bounding it. The path requires an application to process attacker-controlled HTML; resource exhaustion raises MemoryError or freezes the host.

The record

CVE
CVE-2025-46656
Published
Apr 26, 2025
Updated
Apr 29, 2025
Vendor
Matthew Tretter
Product
Markdownify
Classifications
CWE-1284, T1499
Attack vector
local
Privileges
unauthenticated

Timeline

How it unfolded

  1. Apr 26, 2025CVE publishedPublication date reported by the CVE source.
  2. Apr 29, 2025Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=0 <0.14.1

What conditions does exploitation require?

Attack vectorlocal
Required privilegesunauthenticated

What is affected?

Matthew Tretter · Markdownifyversion=0 <0.14.1

Published CVSS scores

3.3NIST NVDCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L
2.9MITRECVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-1284Improper Validation of Specified Quantity in Input
T1499Endpoint Denial of Service

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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