CVE-2026-40890: The package `github.com/gomarkdown/markdown` is a Go library for parsing Markdown text and rendering as HTML

Q: How do I fix CVE-2026-40890?

markdown: upgrade to 2026-04-10. Exact commands for each OS are on this page.

Q: Is CVE-2026-40890 being exploited?

CVE-2026-40890 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-2026-40890 affect?

CVE-2026-40890 affects markdown. Severity is high (CVSS 7.5). The package `github.com/gomarkdown/markdown` is a Go library for parsing Markdown text and rendering as HTML. Processing a malformed input containing a character anywhere in the remaining text with a

This week

HIGH 7.5REMOTEUPGRADE

CVE-2026-40890 is a high-severity flaw (CVSS 7.5) affecting markdown. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

The package `github.com/gomarkdown/markdown` is a Go library for parsing Markdown text and rendering as HTML. Processing a malformed input containing a < character that is not followed by a > character anywhere in the remaining text with a SmartypantsRenderer will lead to Out of Bounds read or a panic. This vulnerability is fixed with commit 759bbc3e32073c3bc4e25969c132fc520eda2778.

Why this priority

High severity
Public exploit reference
Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	7.5 (High)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	0.3% (top 72%)
CISA exploited list	No
Weakness	CWE-125
Published	2026-04-21
Last modified	2026-10-26

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

Last updated 2026-10-26 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-04-21 20:17 UTCPublished CVE record published
2026-10-26 21:10 UTCUpdated Record last modified

gomarkdown markdown UPGRADE

Affected: < 2026-04-10

Fixed in: 2026-04-10

Safe to downgrade to: no unaffected older release

1. Check installed version

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

2. UPGRADE to 2026-04-10 (Debian / Ubuntu)

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

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade markdown

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-2026-40890?

markdown: upgrade to 2026-04-10. Exact commands for each OS are on this page.

Is CVE-2026-40890 being exploited?

CVE-2026-40890 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-2026-40890 affect?

CVE-2026-40890 affects markdown. Severity is high (CVSS 7.5). The package `github.com/gomarkdown/markdown` is a Go library for parsing Markdown text and rendering as HTML. Processing a malformed input containing a < character that is not followed by a > character anywhere in the remaining text with a

How urgent is CVE-2026-40890?

Priority 43/100. High severity; Public exploit reference; Remotely exploitable, no login, no user action

Software pages

GitHub vulnerabilities

References

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