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Fencer Vulns
medium 6.5

CVE-2020-5238 json

Denial of service in table parsing in cmark-gfm

published 2020-07-01 6 y ago modified 2026-06-17 4 mo ago also EUVD-2020-26457 , RSEC-2023-6

cvss
6.5
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
1.6%
EPSS 1.6% chance of exploitation in 30 days, percentile 75%
public exploits
0
none known

Summary

The table extension in GitHub Flavored Markdown before version 0.29.0.gfm.1 takes O(n * n) time to parse certain inputs. An attacker could craft a markdown table which would take an unreasonably long time to process, causing a denial of service. This issue does not affect the upstream cmark project. The issue has been fixed in version 0.29.0.gfm.1.

Patch / fix

  • cran commonmark 1.8
  • github_flavored_markdown_project github_flavored_markdown 0.29.0.gfm.1
  • cmark-gfm Debian 14, Debian 13, Debian 12 0.29.0.gfm.2-1
  • python-cmarkgfm Debian 14, Debian 13, Debian 12 0.7.0-1
  • haskell-cmark-gfm Debian 14, Debian 13, Debian 12 0.2.1+ds1-1
  • r-cran-commonmark Debian 14, Debian 13, Debian 12 1.8.0-1
  • ruby-commonmarker Debian 14, Debian 13, Debian 12 0.21.0-1

debian advisories DEBIAN-CVE-2020-5238

  • pandoc RHEL 8 2.0.6-5.el8
  • pandoc-common RHEL 8 2.0.6-5.el8

red hat advisories RHSA-2021:1972

  • pandoc AlmaLinux 8 2.0.6-5.el8
  • pandoc-common AlmaLinux 8 2.0.6-5.el8

almalinux advisories ALSA-2021:1972

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2020-5238 updated cvss 6.5

cmark-gfm: Exponential time to parse certain inputs could lead to DoS

  • Red Hat CodeReady Linux Builder (v. 8) pandoc 2.0.6-5.el8, pandoc-common 2.0.6-5.el8
    fixed: vendor fix RHSA-2021:1972

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

Exploit prediction

1.57% chance of exploitation in the next 30 days, higher than 75% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 3.1 6.5 CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
NVD 3.1 6.5 CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
NVD 2.0 4.0 AV:N/AC:L/Au:S/C:N/I:N/A:P

Affected packages

ecosystem package affected fixed in
cran commonmark
>=0.2, <1.8
1.8

Affected products

  • github cmark-gfm

Classification

Weakness
  • CWE-20 Improper Input Validation

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.