Showdown through 2.1.0 contains a cross-site scripting vulnerability in the makehtml link and image subparsers, which fail to escape double quotes in destination URLs placed into href and src attributes. Attackers can craft markdown links or images containing a double quote followed by onerror or onmouseover handlers to execute script when victims view rendered HTML.
CVE-2026-104477
MEDIUMPre-NVD 6.16.1—Trending — 4 sources updated this week
EchelonGraph scoreHIGH confidence
Score 6.1 from GitHub Security Advisory published 2026-10-03. A secondary CVSS source baseline 6.1; sources differ by 0.0.
Triggered by: GitHub Security Advisory CVSS
Sources: epss, ghsa, secondary
6.1EG
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
- Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS PROB: 0.2%CVSS: 6.1Exploit: None knownExposed services: Not assessed
An upstream fix is merged but not yet released — mitigate (WAF / firewall / segmentation) until the release ships, then apply it.
- CVSS v3
- 6.1
- EG Score
- 6.1MEDIUMhigh confidence
- EG Risk
- 32EG Risk 32/100CISA SSVC
EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).
How it’s computedSeverity61% × 45%Exploitation0% × 40%Automatability30% × 15%CISA SSVC: Track at low or medium mission impact; Track or Attend at high (mission-essential systems).Action: An upstream fix is merged but not yet in a tagged release. Restrict network exposure of the affected system or apply the vendor's mitigation within your standard update timelines at low or medium mission impact and sooner than that at high until it ships, then apply the release. - EPSS PROB
- 0.2%
- EPSS %ILE
- 7th
- KEV
- Not listed
CISA SSVCTrack at low or medium mission impact; Track or Attend at high (mission-essential systems).
An upstream fix is merged but not yet in a tagged release. Restrict network exposure of the affected system or apply the vendor's mitigation within your standard update timelines at low or medium mission impact and sooner than that at high until it ships, then apply the release.
Exploitation none (no KEV listing, exploit record or EPSS ≥ 50%) · Automatable unknown (not published for this CVE) · Technical impact partial (CVSS below 9.0). Mission impact is CISA's Mission & Well-being decision point, and only you can judge it: high means the affected system is essential to your organisation's mission, or its compromise could cause irreversible harm to people. CISA's decision table
Published
October 2, 2026
Last Modified
October 3, 2026
Advisory Details (3)
Auto-updated Oct 2, 2026Upstream fix merged — awaiting tagged release. Sources: github_commit.
generic
Showdown through 2.1.0 XSS via unescaped quote in href and src attributes | Advisories | VulnCheck
https://www.vulncheck.com/advisories/showdown-through-2.1.0-xss-via-unescaped-quote-in-href-and-src-attributesgeneric
GitHub - showdownjs/showdown: A bidirectional Markdown to HTML to Markdown converter written in Javascript · GitHub
https://github.com/showdownjs/showdowngithub_commit
commit 4fb992cd2663 (showdownjs/showdown)
Fix landed in showdownjs/showdown commit 4fb992cd2663 — awaiting tagged release
https://github.com/showdownjs/showdown/commit/4fb992cd26631c108ec0410342630c80207ec7c6Vendor Advisories for CVE-2026-104477(1)
These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.
Weakness Classification(1)
MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.
Data Freshness Timeline
(refreshed 9× in last 7d / 9× in last 30d)
Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.
- 2026-10-04 23:57 UTCEG score recompute
- 2026-10-04 23:57 UTCGHSA enrichment
- 2026-10-04 23:21 UTCEPSS rescore
- 2026-10-04 00:08 UTCEG score recompute
- 2026-10-04 00:08 UTCGHSA enrichment
- 2026-10-03 14:25 UTCEPSS rescore
- 2026-10-03 00:19 UTCEG score recompute
- 2026-10-02 23:32 UTCEG score recompute
- 2026-10-02 23:30 UTCMITRE cvelistV5first tracked
Related CVEs(same CWE)
Frequently asked(5)
What is CVE-2026-104477?
CVE-2026-104477 is a medium vulnerability published on October 2, 2026. Showdown through 2.1.0 contains a cross-site scripting vulnerability in the makehtml link and image subparsers, which fail to escape double quotes in destination URLs placed into href and src attributes. Attackers can craft markdown links or images containing a double quote followed by onerror or…
When was CVE-2026-104477 disclosed?
CVE-2026-104477 was first published on October 2, 2026, with the most recent update on October 3, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-104477 actively exploited?
CVE-2026-104477 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0.2% probability of exploitation in the next 30 days (7th percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2026-104477?
CVE-2026-104477 has a CVSS base score of 6.1 (a secondary CVSS source that NVD displays; NVD's own analysis pending).
How do I remediate CVE-2026-104477?
An upstream fix for CVE-2026-104477 has been merged but is not yet in a tagged release. Until it ships, restrict network exposure of the affected system or apply the vendor's mitigation, then update to the release that contains the fix. The vendor advisories EchelonGraph has for CVE-2026-104477 are linked in the Vendor Advisories panel on this page.
Dependency Blast Radius
Explore the affected products and dependency analysis for CVE-2026-104477
Is Your Infrastructure Affected by CVE-2026-104477?
EchelonGraph automatically scans your cloud infrastructure and maps CVE exposure using blast radius analysis.