CVE-2022-39209Public exploitNetwork attack vector

Denial of service via repeated bracket-stack scans

Published Sep 15, 2022 · Updated Apr 23, 2025

Algorithmic-complexity denial of service in GitHub cmark-gfm before 0.29.0.gfm.6 allows remote attackers to exhaust resources via crafted Markdown. The autolink extension repeatedly walks the active bracket stack in cmark_inline_parser_in_bracket for nested image-link markers instead of tracking bracket state. The consuming application must enable autolinks and parse attacker-controlled Markdown; a crafted repeated marker sequence can monopolize processing and interrupt that service.

CVSS severity7.5
High
EPSS probability2.14%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Algorithmic-complexity denial of service in GitHub cmark-gfm before 0.29.0.gfm.6 allows remote attackers to exhaust resources via crafted Markdown. The autolink extension repeatedly walks the active bracket stack in cmark_inline_parser_in_bracket for nested image-link markers instead of tracking bracket state. The consuming application must enable autolinks and parse attacker-controlled Markdown; a crafted repeated marker sequence can monopolize processing and interrupt that service.

The record

CVE
CVE-2022-39209
Published
Sep 15, 2022
Updated
Apr 23, 2025
Vendor
Twitter
Product
cmark-gfm
Classifications
CWE-407, CWE-400, T1499.004
Attack vector
network
Privileges
Unavailable

Timeline

How it unfolded

  1. Sep 15, 2022CVE publishedPublication date reported by the CVE source.
  2. Apr 23, 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=< 0.29.0.gfm.6

What conditions does exploitation require?

Attack vectornetwork
Required privilegesUnavailable in this record.

What is affected?

Twitter · cmark-gfmversion=< 0.29.0.gfm.6

Published CVSS scores

7.5GitHub, Inc.CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
6.5NVDCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

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.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

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

Weakness, pattern, technique

CWE-407Inefficient Algorithmic Complexity
CWE-400Uncontrolled Resource Consumption
T1499.004Application or System Exploitation

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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