CVE-2026-102941
7.5HighPublished 16 Oct 2026 · NVD status: Deferred · AI triage by gemini-3.8-flash
- Attack vector
- Network
- Complexity
- Low
- Privileges needed
- None
- User interaction
- None
- Impact
- High impact on availability
- Weakness
- CWE-125
Impact
Remote unauthenticated attackers can crash the application process, causing a denial of service. They only need to supply Markdown containing short or empty link destinations when Safelink is enabled, or pass short URLs to parser.IsSafeURL.
Root cause
parser.IsSafeURL slices a URL slice before checking its length against the prefix length, causing an out-of-bounds slice panic on short strings.
Affected systems
github.com/gomarkdown/markdown prior to commit 0.0.0-20260724235538-61af6e1e6971
CVSS v3.1 · CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Fix & remediation
Upgrade github.com/gomarkdown/markdown to 0.0.0-20260724235538-61af6e1e6971 or later. If patching immediately is impossible, recover panics around calls to markdown.ToHTML or avoid using html.Safelink on untrusted input.
$ go get github.com/gomarkdown/markdown@61af6e1e69710c5ca13cfbaaaa1bc11bc763a8a9 && go mod tidyAI-suggested. Run it in staging first and check it against the vendor advisory. Why?
NVD 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.