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.
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Mon, 26 Oct 2026 18:30:00 +0000
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Fri, 23 Oct 2026 11:00:00 +0000
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Gomarkdown
Gomarkdown markdown |
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Gomarkdown
Gomarkdown markdown |
Mon, 19 Oct 2026 12:30:00 +0000
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threat_severity
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Fri, 16 Oct 2026 15:45:00 +0000
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| 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. | |
| Title | gomarkdown/markdown IsSafeURL panics on short URLs | |
| Weaknesses | CWE-125 | |
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cvssV3_1
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Status: PUBLISHED
Assigner: GitHub_M
Published: 2026-10-16T15:38:18.086Z
Updated: 2026-10-26T17:37:11.962Z
Reserved: 2026-09-29T20:24:43.341Z
Link: CVE-2026-102941
Updated: 2026-10-26T17:36:07.163Z
Status : Deferred
Published: 2026-10-16T16:16:52.937
Modified: 2026-10-26T18:17:23.420
Link: CVE-2026-102941