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CVE-2020-5238

Denial of service in table parsing in cmark-gfm

MEDIUM
6.5
CVSS Score
Published: July 1, 2020 at 11:05 PM UTC
Updated: June 17, 2026 at 03:21 AM UTC
3 products affected across 3 vendorsFedoraGitHub Flavored MarkdownCmark Gfm

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Severity
MEDIUM6.5
Exploit prediction
EPSS 2%

Description

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.

Affected

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

Fedora· Fedora Projectrpm
95%
313233
GitHub Flavored Markdown· GitHub Flavored Markdown Project
95%
v < 0.29.0.gfm.1
Affected range stops below 0.29.0.gfm.1, so it looks safe — our inference, not a vendor statement
Cmark Gfm· GitHubgithub-action
60%
v < 0.29.0.gfm.1
Affected range stops below 0.29.0.gfm.1, so it looks safe — our inference, not a vendor statement

References (5)

x_refsource_MISCPatchThird Party Advisory
Source: [email protected]
https://github.com/github/cmark-gfm/commit/85d895289c5ab67f988ca659493a64abb5fec7b4
x_refsource_CONFIRMThird Party Advisory
Source: [email protected]
https://github.com/github/cmark-gfm/security/advisories/GHSA-7gc6-9qr5-hc85
Vendor Advisoryx_refsource_FEDORA
Source: [email protected]
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/TCDHBTUFIOYRIS5HAS6PZNBNMB7IOAX3/
Vendor Advisoryx_refsource_FEDORA
Source: [email protected]
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/WMQFOQQCWOAMQ4I2XIVCVOXXIJ75HDCW/
Vendor Advisoryx_refsource_FEDORA
Source: [email protected]
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/ZGJH2A4VAV54X6NSCNNGSEIGIIY5N2VR/

CVSS

6.5MEDIUMGitHub_M
Attack Vector
NETWORK
Complexity
LOW
Privileges
LOW
User Interaction
NONE
Scope
UNCHANGED
Confidentiality
NONE
Integrity
NONE
Availability
HIGH
Vector?

Quick Info

StatusMODIFIED
CWE
CWE-20

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