CVE-2022-34749: Mistune Mistune Vulnerable To Catastrophic Backtracking Vulnerability

HIGH
Advisory Identifier: GHSA-fw3v-x4f2-v673
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CVSS 8.6
CWE-1333
Published
Advisory Summary

CVE-2022-34749 is a HIGH (CVSS 8.6) mistune vulnerable to catastrophic backtracking vulnerability (CWE-1333: Inefficient Regular Expression Complexity) affecting Mistune libraries in the PyPI ecosystem. The issue involves mistune vulnerable to catastrophic backtracking. Remediation is available by upgrading affected packages to version 2.0.3.

CVE-2022-34749 at a Glance

CVE Identifier CVE-2022-34749
GHSA Identifier GHSA-fw3v-x4f2-v673
Severity HIGH
CVSS v3.1 Base Score 8.6
CWE Classification CWE-1333: Inefficient Regular Expression Complexity
Affected Product Mistune
Package Ecosystem PyPI
Published Date
Last Updated

Security Impact

CVSS: 8.6

The security impact metrics below are parsed directly from the CVSS v3.1 vector string (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:H).

Attack Vector Network (AV:N)
Attack Complexity Low (AC:L)
Privileges Required None (PR:N)
User Interaction None (UI:N)
Scope Unchanged (S:U)
Confidentiality Low (C:L)
Integrity Low (I:L)
Availability High (A:H)

How to Fix CVE-2022-34749

To remediate this vulnerability, upgrade all affected Mistune dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

mistune fixed: 2.0.3 
pip install mistune>=2.0.3
Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release: 

pip show mistune

How to Check if You Are Affected

To determine whether your Python environment is affected by CVE-2022-34749, inspect your installed packages using pip:

pip show mistune

Analyze the terminal output to locate any version of Mistune in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 2.0.3), your application is affected.

Note: The pip show mistune command checks currently installed packages in your active Python environment.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-1333: Inefficient Regular Expression Complexity, where the product uses a regular expression with a worst-case computational complexity that is inefficient and possibly exponential. In Mistune, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.

Source Advisory Statement

In Mistune through 2.0.2, support of inline markup is implemented by using regular expressions that can involve a high amount of backtracking on certain edge cases. This behavior is commonly named catastrophic backtracking.

CVE-2022-34749 Affected Mistune Versions

1 component(s)
Fixed Versions:
2.0.3
Product / Package Ecosystem Affected Versions Fixed Version
mistune
pypi/mistune
PyPI
≥ 2.0.0a1
< 2.0.3
2.0.3

References

NVD — CVE-2022-34749 NVD
https://nvd.nist.gov/vuln/detail/CVE-2022-34749
Mistune Source Repository REPOSITORY
https://github.com/lepture/mistune/issues/314#issuecomment-1223972386
Security Fix Commit FIX COMMIT
https://github.com/lepture/mistune/commit/a6d43215132fe4f3d93f8d7e90ba83b16a0838b2
Security Fix Commit FIX COMMIT
https://github.com/lepture/mistune/commit/ca1e7b506850f4e488823fc7338b49a8f9852718
Mistune Source Repository REPOSITORY
https://github.com/lepture/mistune
Mistune Source Repository REPOSITORY
https://github.com/lepture/mistune/releases
Mistune Source Repository REPOSITORY
https://github.com/pypa/advisory-database/tree/main/vulns/mistune/PYSEC-2022-237.yaml
lists.fedoraproject.org/archives/list/packa... WEB
https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/TQHXITQ2DSBYOILKHXBSBB7PFBPZHF63

Frequently Asked Questions

What is CVE-2022-34749?
CVE-2022-34749 is a security vulnerability in Mistune involving Mistune vulnerable to catastrophic backtracking under CWE-1333: Inefficient Regular Expression Complexity.
Which Mistune versions are affected?
Affected versions include releases prior to 2.0.3 across affected packages: mistune.
What version fixes CVE-2022-34749?
Upgrading to 2.0.3 (or the latest patched release for your respective branch) resolves the vulnerability.
Is mistune affected?
Yes, mistune is affected in releases prior to 2.0.3. Upgrade your dependency to 2.0.3 or later.
What is the CVSS score of CVE-2022-34749?
CVE-2022-34749 has a CVSS v3.1 base score of 8.6 (HIGH) with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:H.
What CWE is associated with CVE-2022-34749?
CVE-2022-34749 is classified under CWE-1333: Inefficient Regular Expression Complexity (The product uses a regular expression with a worst-case computational complexity that is inefficient and possibly exponential.).
How can I check PyPI dependencies for CVE-2022-34749?
Run the dependency tree command: 'pip show mistune'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON OSV v1.5 Schema
Normalized schema output
View Raw JSON 
{
  "schema_version" : "1.4.0",
  "id" : "GHSA-fw3v-x4f2-v673",
  "modified" : "2024-09-25T20:07:25Z",
  "published" : "2022-07-26T00:00:27Z",
  "aliases" : [ "CVE-2022-34749" ],
  "summary" : "Mistune vulnerable to catastrophic backtracking",
  "details" : "In Mistune through 2.0.2, support of inline markup is implemented by using regular expressions that can involve a high amount of backtracking on certain edge cases. This behavior is commonly named catastrophic backtracking.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:H"
  }, {
    "type" : "CVSS_V4",
    "score" : "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:L/VA:H/SC:N/SI:N/SA:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "PyPI",
      "name" : "mistune"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "2.0.0a1"
      }, {
        "fixed" : "2.0.3"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2022-34749"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/lepture/mistune/issues/314#issuecomment-1223972386"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/lepture/mistune/commit/a6d43215132fe4f3d93f8d7e90ba83b16a0838b2"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/lepture/mistune/commit/ca1e7b506850f4e488823fc7338b49a8f9852718"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/lepture/mistune"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/lepture/mistune/releases"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/pypa/advisory-database/tree/main/vulns/mistune/PYSEC-2022-237.yaml"
  }, {
    "type" : "WEB",
    "url" : "https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/TQHXITQ2DSBYOILKHXBSBB7PFBPZHF63"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-1333" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2022-07-29T22:24:56Z",
    "nvd_published_at" : "2022-07-25T23:15:00Z"
  }
}