CVE-2026-102941 gomarkdown/markdown IsSafeURL panics on short URLs
An attacker can cause a denial of service by providing short URLs that trigger a panic in the gomarkdown library's URL safety check.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-102941?
CVE-2026-102941 is a high-severity denial of service vulnerability in gomarkdown markdown, published on 16 Oct 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
The package github.com/gomarkdown/markdown is a Go library for parsing Markdown text and rendering as HTML. Prior to 0.0.0-20260724235538-61af6e1e6971, parser.IsSafeURL in parser/parser.go slices url[:nPath] before the len(url) >= nPath guard. A short destination causes a slice-bounds panic when the loop reaches a relative-path prefix for which len(url) < nPath and cap(url) < nPath. The one-byte destination / is an explicit non-panic counterexample because it matches the first valid path and returns before a longer prefix is sliced. Demonstrated panic cases include empty, ., and .. destinations under those conditions. The panic is reachable when markdown.ToHTML renders untrusted Markdown with html.Safelink enabled, including an empty link destination, and is also reachable by callers that pass a short attacker-controlled URL directly to the exported parser.IsSafeURL function. An uncaught panic can terminate the calling process and cause denial of service. This issue is fixed in 0.0.0-20260724235538-61af6e1e6971.
Weakness: CWE-125
Which versions are affected by CVE-2026-102941?
2 open source packages ship an affected version, including github.com/gomarkdown/markdown.
| Package | Affected | Fixed in |
|---|---|---|
github.com/gomarkdown/markdown Go | All versions | 0.0.0-20260724235538-61af6e1e6971 |
github.com/gomarkdown/markdown Go | All versions | 0.0.0-20260724235538-61af6e1e6971 |
How do I fix CVE-2026-102941?
Upgrade github.com/gomarkdown/markdown to 0.0.0-20260724235538-61af6e1e6971 or later.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2026-102941 being exploited?
There is no known exploitation of CVE-2026-102941 in the wild and no public exploit code.
Sources
Also known as DEBIAN-CVE-2026-102941, ECHO-8fac-c542-ba3d, GHSA-cv23-7vc5-jfh7, MINI-cp4v-cwg3-9h7j, UBUNTU-CVE-2026-102941.