Vulnerability · Published Apr 21, 2026 · Assigned by GitHub_M
CVE-2026-40890github.com/gomarkdown/markdown: Out-of-bounds Read in SmartypantsRenderer
High 7.5
In plain English
A high-severity out-of-bounds read in markdown from gomarkdown. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.3% (higher than 28% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Official description
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.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian:12 | golang-github-gomarkdown-markdown | no fix listed | DEBIAN-CVE-2026-40890 |
| Debian:13 | golang-github-gomarkdown-markdown | no fix listed | DEBIAN-CVE-2026-40890 |
| Debian:14 | golang-github-gomarkdown-markdown | 0.0~git20260725.8435af3-1 | DEBIAN-CVE-2026-40890 |
| Go | github.com/gomarkdown/markdown | 0.0.0-20260411013819-759bbc3e3207 | GHSA-77fj-vx54-gvh7 |
| Go | github.com/gomarkdown/markdown | 0.0.0-20260411013819-759bbc3e3207 | GO-2026-5208 |
| Ubuntu:24.04:LTS | golang-github-gomarkdown-markdown | no fix listed | UBUNTU-CVE-2026-40890 |
| Ubuntu:25.10 | golang-github-gomarkdown-markdown | no fix listed | UBUNTU-CVE-2026-40890 |
| Ubuntu:26.04:LTS | golang-github-gomarkdown-markdown | no fix listed | UBUNTU-CVE-2026-40890 |
| Ubuntu:26.10 | golang-github-gomarkdown-markdown | no fix listed | UBUNTU-CVE-2026-40890 |
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| gomarkdown | markdown | < 759bbc3e32073c3bc4e25969c132fc520eda2778 |
Weakness: CWE-125 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H