CVE-2026-55839

HIGHPre-NVD 8.78.7—
EchelonGraph scoreMEDIUM confidence

This high-severity CVE scores 8.7 under a secondary CVSS source (NVD's own analysis pending). EPSS exploit probability: 0.3%, top 77% of all CVEs by exploit prediction. GitHub Security Advisory data not yet ingested — confidence will rise once GHSA publishes (typical lag: hours to days for open-source ecosystem CVEs; never for infrastructure-only CVEs).

Triggered by: NVD CVSS baseline
Sources: epss, secondary
Trending — 3 sources updated this week
8.7EG
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 0%CVSS: 8.7Exploit: None knownExposed: 0

No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.

Kestra is an open-source, event-driven orchestration platform. Prior to 1.3.24, Kestra's custom Markdown parser in ui/src/utils/markdown_plugins/link.ts allows a user with permission to create or update a Flow description to inject JavaScript event-handler attributes through the custom [[link]] syntax, causing stored cross-site scripting when another user opens the description or information panel in the Flow list. This issue is fixed in version 1.3.24.

CVSS v3
8.7
EG Score
8.7(medium)
EG Risk
39(Track)
EG Risk 39/100SSVC: Track

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 computed
Severity87% × 45%
Exploitation0% × 40%
Automatability0% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
0%
EPSS %ILE
23%
KEV
Not listed

Published

August 18, 2026

Last Modified

August 18, 2026

Advisory Details (4)

Auto-updated Aug 18, 2026
🔬 Proof of concept available. Patch available. Sources: github_release, github, github_pr, github_commit.
github_release Patch Available

v1.3.24

Patch available: kestra-io/kestra v1.3.24

https://github.com/kestra-io/kestra/releases/tag/v1.3.24
github_commit Patch Available

commit 6c8e6d099ed1 (kestra-io/kestra)

Patch available: kestra-io/kestra v1.3.24 (contains commit 6c8e6d099ed1)

https://github.com/kestra-io/kestra/commit/6c8e6d099ed172cbb6b003b7fb30b7bb1f8f710e
github_pr Patch Available

fix: render router-md as anchors using linkify

Patch available: kestra-io/kestra v1.3.24 (PR #16835 merged 2026-06-16)

https://github.com/kestra-io/kestra/pull/16835
github Patch Available🟡 PoC Available

Stored XSS via custom Markdown [[link]] attribute injection in Kestra · Advisory · kestra-io/kestra · GitHub

https://github.com/kestra-io/kestra/security/advisories/GHSA-34pm-923j-7wf8

Vendor Advisories for CVE-2026-55839(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 8× in last 7d / 8× 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.

  1. 2026-08-20 22:55 UTCEPSS rescore
  2. 2026-08-19 20:24 UTCEG score recompute
  3. 2026-08-19 17:04 UTCEPSS rescore
  4. 2026-08-18 18:24 UTCEG score recompute
  5. 2026-08-18 18:00 UTCEG score recompute
  6. 2026-08-18 16:31 UTCEG score recompute
  7. 2026-08-18 15:45 UTCEG score recompute
  8. 2026-08-18 15:44 UTCMITRE cvelistV5first tracked

Related CVEs(same CWE)

Frequently asked(5)

What is CVE-2026-55839?
CVE-2026-55839 is a high vulnerability published on August 18, 2026. Kestra is an open-source, event-driven orchestration platform. Prior to 1.3.24, Kestra's custom Markdown parser in ui/src/utils/markdown_plugins/link.ts allows a user with permission to create or update a Flow description to inject JavaScript event-handler attributes through the custom [[link]]…
When was CVE-2026-55839 disclosed?
CVE-2026-55839 was first published in the National Vulnerability Database on August 18, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-55839 actively exploited?
CVE-2026-55839 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0% probability of exploitation in the next 30 days, which ranks it in the top 77.1% of all scored CVEs.
What is the CVSS score of CVE-2026-55839?
CVE-2026-55839 has a CVSS v3 base score of 8.7 (NVD).
How do I remediate CVE-2026-55839?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-55839, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

Dependency Blast Radius

Explore the affected products and dependency analysis for CVE-2026-55839

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