CVE-2021-41168: Snudown is a reddit-specific fork of the Sundown Markdown parser used by GitHub, with Python integration added

Q: How do I fix CVE-2021-41168?

snudown: upgrade to 1.7.0. Exact commands for each OS are on this page.

Q: Is CVE-2021-41168 being exploited?

CVE-2021-41168 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2021-41168 affect?

CVE-2021-41168 affects snudown. Severity is medium (CVSS 6.5). Snudown is a reddit-specific fork of the Sundown Markdown parser used by GitHub, with Python integration added. In affected versions snudown was found to be vulnerable to denial of service attacks to its reference table implementation. Refe

Q: How urgent is CVE-2021-41168?

Priority 42/100. Public exploit reference

This month

MEDIUM 6.5UPGRADE

CVE-2021-41168 is a medium-severity flaw (CVSS 6.5) affecting snudown. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Snudown is a reddit-specific fork of the Sundown Markdown parser used by GitHub, with Python integration added. In affected versions snudown was found to be vulnerable to denial of service attacks to its reference table implementation. References written in markdown ` [reference_name]: https://www.example.com` are inserted into a hash table which was found to have a weak hash function, meaning that an attacker can reliably generate a large number

Why this priority

Public exploit reference

A fixed release or distro patch exists.

Risk facts

CVSS score	6.5 (Medium)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	Low
User interaction	None
EPSS exploit chance	0.8% (top 44%)
CISA exploited list	No
Weakness	CWE-20, CWE-327, CWE-400, CWE-407
Published	2021-10-21
Last modified	2026-06-17

Publisher (CNA): GitHub, Inc. · Vendor: reddit

Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2021-10-21 20:15 UTCPublished CVE record published
2026-06-17 04:08 UTCUpdated Record last modified

reddit snudown UPGRADE

Affected: < 1.7.0

Fixed in: 1.7.0

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy snudown || rpm -q snudown || snudown --version

2. UPGRADE to 1.7.0 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade snudown

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade snudown

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2021-41168?

snudown: upgrade to 1.7.0. Exact commands for each OS are on this page.

Is CVE-2021-41168 being exploited?

CVE-2021-41168 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2021-41168 affect?

CVE-2021-41168 affects snudown. Severity is medium (CVSS 6.5). Snudown is a reddit-specific fork of the Sundown Markdown parser used by GitHub, with Python integration added. In affected versions snudown was found to be vulnerable to denial of service attacks to its reference table implementation. Refe

How urgent is CVE-2021-41168?

Priority 42/100. Public exploit reference

Software pages

Python vulnerabilities · GitHub vulnerabilities

References

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