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Fencer Vulns
high 7.5

CVE-2026-40890 json

github.com/gomarkdown/markdown: Out-of-bounds Read in SmartypantsRenderer

published 2026-04-14 6 mo ago modified 2026-10-26 13 d ago also EUVD-2026-24280 , GHSA-77fj-vx54-gvh7 , GO-2026-5208

cvss
7.5
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.3%
EPSS 0.3% chance of exploitation in 30 days, percentile 28%
public exploits
0
none known

Summary

The package `github.com/gomarkdown/markdown` is a Go library for parsing Markdown text and rendering as HTML. Processing a malformed input containing a < character that is not followed by a > character anywhere in the remaining text with a SmartypantsRenderer will lead to Out of Bounds read or a panic. This vulnerability is fixed with commit 759bbc3e32073c3bc4e25969c132fc520eda2778.

Patch / fix

  • go github.com/gomarkdown/markdown 0.0.0-20260411013819-759bbc3e3207
  • gomarkdown markdown 0.0.0-20260411013819-759bbc3e3207
  • golang-github-gomarkdown-markdown Debian 14 0.0~git20260725.8435af3-1

debian advisories DEBIAN-CVE-2026-40890

  • govulncheck-vulndb SLES 16.0, SLES for SAP applications 16.0 0.0.20260727T201416-160000.1.1

suse advisories SUSE-SU-2026:23216-1SUSE-SU-2026:23227-1

  • govulncheck-vulndb openSUSE Leap 16.0 0.0.20260727T201416-160000.1.1

opensuse advisories openSUSE-SU-2026:21551-1

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2026-40890 updated cvss 7.5

github.com/gomarkdown/markdown: github.com/gomarkdown/markdown: Denial of Service via malformed Markdown input

  • Red Hat Multicluster Global Hub 1.4.9 multicluster-globalhub/multicluster-globalhub-grafana-rhel9 1779579439
    fixed: vendor fix RHSA-2026:22347
  • Red Hat Multicluster Global Hub 1.6.5 multicluster-globalhub/multicluster-globalhub-grafana-rhel9 1780167118
    fixed: vendor fix RHSA-2026:23345
  • Red Hat Multicluster Global Hub 1.7.3 multicluster-globalhub/multicluster-globalhub-grafana-rhel9 1779925273
    fixed: vendor fix RHSA-2026:24503
  • Red Hat Advanced Cluster Management for Kubernetes 2.15 rhacm2/acm-grafana-rhel9 1780677003
    fixed: vendor fix RHSA-2026:24539
  • Red Hat multicluster global hub 1.5.3 multicluster-globalhub/multicluster-globalhub-grafana-rhel9 1778867753
    fixed: vendor fix RHSA-2026:21769
  • Red Hat Kube Descheduler Operator kube-descheduler-operator/descheduler-rhel9
    not affected: vulnerable code not in execute path
  • Red Hat Multicluster Global Hub 1.4.9 multicluster-globalhub/multicluster-globalhub-agent-rhel9 1779838819, multicluster-globalhub/multicluster-globalhub-manager-rhel9 1779839447, multicluster-globalhub/multicluster-globalhub-rhel9-operator 1779887217, multicluster-globalhub/multicluster-globalhub-operator-bundle 1779891163, multicluster-globalhub/multicluster-globalhub-postgres-exporter-rhel9 1779147132 Red Hat Multicluster Global Hub 1.6.5 multicluster-globalhub/multicluster-globalhub-agent-rhel9 1780320809, multicluster-globalhub/multicluster-globalhub-manager-rhel9 1780321673, multicluster-globalhub/multicluster-globalhub-rhel9-operator 1779839087, multicluster-globalhub/multicluster-globalhub-operator-bundle 1780370487, multicluster-globalhub/multicluster-globalhub-postgres-exporter-rhel9 1779839762 Red Hat Multicluster Global Hub 1.7.3 multicluster-globalhub/multicluster-globalhub-agent-rhel9 1780361828, multicluster-globalhub/multicluster-globalhub-manager-rhel9 1780615638, multicluster-globalhub/multicluster-globalhub-rhel9-operator 1779887500, multicluster-globalhub/multicluster-globalhub-operator-bundle 1780616828, multicluster-globalhub/multicluster-globalhub-postgres-exporter-rhel9 1779815431 Red Hat Advanced Cluster Management for Kubernetes 2.15 rhacm2/thanos-rhel9 1780908155, rhacm2/acm-cli-rhel9 1780415683, rhacm2/console-rhel9 1780876734, rhacm2/prometheus-rhel9 1780906025, rhacm2/acm-search-v2-rhel9 1780877544, rhacm2/node-exporter-rhel9 1780876985, +39 more Red Hat multicluster global hub 1.5.3 multicluster-globalhub/multicluster-globalhub-agent-rhel9 1779828691, multicluster-globalhub/multicluster-globalhub-manager-rhel9 1779828813, multicluster-globalhub/multicluster-globalhub-rhel9-operator 1779828536, multicluster-globalhub/multicluster-globalhub-operator-bundle 1779837290, multicluster-globalhub/multicluster-globalhub-postgres-exporter-rhel9 1779835152
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
Proof of concept is public
Automatable
yes
Technical impact
partial
Assessed
6 mo ago

Exploit prediction

0.35% chance of exploitation in the next 30 days, higher than 28% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

  • github.com https://github.com/gomarkdown/markdown/security/advisories/GHSA-77fj-vx54-gvh7 referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
CNA 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
GitHub 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Affected packages

ecosystem package affected fixed in
go github.com/gomarkdown/markdown
<0.0.0-20260411013819-759bbc3e3207
0.0.0-20260411013819-759bbc3e3207

Affected products

  • gomarkdown markdown

Classification

Weakness

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

CPEs and fixed versions use Anchore's correction of NVD's data: Added CPE configurations because not yet analyzed by NVD.