# 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.

- **Severity:** High 7.5 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 16 Oct 2026
- **Updated:** 26 Oct 2026
- **Also known as:** DEBIAN-CVE-2026-102941, ECHO-8fac-c542-ba3d, GHSA-cv23-7vc5-jfh7, MINI-cp4v-cwg3-9h7j, UBUNTU-CVE-2026-102941

## 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 (Out-of-bounds Read)

## Which versions are affected by CVE-2026-102941?

2 open source packages ship an affected version, including github.com/gomarkdown/markdown.


| Package | Ecosystem | 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.

## Is CVE-2026-102941 being exploited?

There is no known exploitation of CVE-2026-102941 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-102941 and fix it if it is affected.

What it is: 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.
Exploitation: There is no known exploitation of CVE-2026-102941 in the wild and no public exploit code.

Affected packages and fixed versions:
- github.com/gomarkdown/markdown (Go): affected all versions; fixed in 0.0.0-20260724235538-61af6e1e6971
- github.com/gomarkdown/markdown (Go): affected all versions; fixed in 0.0.0-20260724235538-61af6e1e6971

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-102941/ (Markdown: https://insights.sbomify.com/CVE-2026-102941/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-102941
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-102941
- OSV: https://osv.dev/vulnerability/CVE-2026-102941

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-102941/
Summaries are generated and may contain mistakes; the official description above is the record.