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Fencer Vulns
high 7.5

CVE-2023-42821 json

github.com/gomarkdown/markdown Out-of-bounds Read while parsing citations

published 2023-09-22 3 y ago modified 2026-09-10 1 mo ago also EUVD-2023-2549 , GHSA-m9xq-6h2j-65r2 , GO-2023-2074

cvss
7.5
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
1.3%
EPSS 1.3% chance of exploitation in 30 days, percentile 69%
public exploits
0
none known

Summary

The package `github.com/gomarkdown/markdown` is a Go library for parsing Markdown text and rendering as HTML. Prior to pseudoversion `0.0.0-20230922105210-14b16010c2ee`, which corresponds with commit `14b16010c2ee7ff33a940a541d993bd043a88940`, parsing malformed markdown input with parser that uses parser.Mmark extension could result in out-of-bounds read vulnerability. To exploit the vulnerability, parser needs to have `parser.Mmark` extension set. The panic occurs inside the `citation.go` file on the line 69 when the parser tries to access the element past its length. This can result in a denial of service. Commit `14b16010c2ee7ff33a940a541d993bd043a88940`/pseudoversion `0.0.0-20230922105210-14b16010c2ee` contains a patch for this issue.

Patch / fix

  • go github.com/gomarkdown/markdown 0.0.0-20230922105210-14b16010c2ee
  • gomarkdown markdown 0.0.0-20230922105210-14b16010c2ee
  • golang-github-gomarkdown-markdown Debian 14, Debian 13 0.0~git20231115.a660076-1

debian advisories DEBIAN-CVE-2023-42821

  • cri-o CBL-Mariner 2.0 1.21.7-2

azure linux advisories AZL-39828

Azure Linux vulnerability data, Copyright (c) Microsoft Corporation, from https://github.com/microsoft/AzureLinuxVulnerabilityData via OSV, under the MIT licence; changed: normalised to fixed package versions per release. MIT

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-2023-42821 updated cvss 6.2

gomarkdown-markdown: Out-of-bounds Read while parsing citations

  • Red Hat All currently supported Red Hat products
    not affected: vulnerable code not present

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

CISA SSVC

Exploitation
Proof of concept is public
Automatable
yes
Technical impact
partial
Assessed
2 y ago

Exploit prediction

1.25% chance of exploitation in the next 30 days, higher than 69% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

  • github.com https://github.com/gomarkdown/markdown/security/advisories/GHSA-m9xq-6h2j-65r2 referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
CNA 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
GitHub 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
NVD 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Affected packages

ecosystem package affected fixed in
go github.com/gomarkdown/markdown
<0.0.0-20230922105210-14b16010c2ee
0.0.0-20230922105210-14b16010c2ee

Affected products

  • gomarkdown markdown

Classification

Weakness

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.

CPEs and fixed versions use Anchore's correction of NVD's data: Add fix versions.