Yamcs is a mission control framework. Prior to 5.9.4, Yamcs reflects an attacker-controlled redirect_uri parameter from GET /auth/authorize into yamcs-core/src/main/resources/auth/templates/authorize.html without adequate HTML escaping by yamcs-core/src/main/java/org/yamcs/http/auth/AuthHandler.java and yamcs-core/src/main/java/org/yamcs/http/HandlerContext.java. A crafted authorization URL can execute JavaScript when opened by a Yamcs user. The script can access browser-held authentication material and transmit it to an attacker, enabling account compromise. This issue is fixed in version 5.9.4.
CVE-2026-55549
MEDIUMPre-NVD 6.56.5
EchelonGraph scoreLOW confidence
This medium-severity CVE scores 6.5 under a secondary CVSS source (NVD's own analysis pending). EPSS exploit-prediction score not yet available (the EPSS model rescores nightly; freshly-published CVEs typically appear within 48 hours). 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: secondary
6.5EG
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
- Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS PROB: 0%CVSS: 6.5Exploit: None knownExposed: 0
No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.
- CVSS v3
- 6.5
- EG Score
- 6.5(low)
- EG Risk
- 34(Track)EG Risk 34/100SSVC: 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 computedSeverity65% × 45%Exploitation0% × 40%Automatability30% × 15%Action: Routine — remediate on your standard cadence. - EPSS PROB
- 0%
- EPSS %ILE
- 29%
- KEV
- Not listed
Published
August 28, 2026
Last Modified
August 28, 2026
Advisory Details (3)
Auto-updated Aug 28, 2026Patch available. Sources: github_release, github, github_commit.
github Patch Available
Reflected XSS in the URL of the Authorize Endpoint · Advisory · yamcs/yamcs · GitHub
https://github.com/yamcs/yamcs/security/advisories/GHSA-rxpg-wjf8-qv9cgithub_release Patch Available
Yamcs 5.9.4
Patch available: yamcs/yamcs yamcs-5.9.4
https://github.com/yamcs/yamcs/releases/tag/yamcs-5.9.4github_commit
commit 4d47d5cdcf5d (yamcs/yamcs)
Fix landed in yamcs/yamcs commit 4d47d5cdcf5d — awaiting tagged release
https://github.com/yamcs/yamcs/commit/4d47d5cdcf5d92c2c5bbbc19feada422923332e3Vendor Advisories for CVE-2026-55549(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 3× in last 7d / 3× 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.
- 2026-08-30 01:22 UTCEPSS rescore
- 2026-08-28 20:25 UTCEG score recompute
- 2026-08-28 18:10 UTCEG score recompute
Related CVEs(same CWE)
Frequently asked(5)
What is CVE-2026-55549?
CVE-2026-55549 is a medium vulnerability published on August 28, 2026. Yamcs is a mission control framework. Prior to 5.9.4, Yamcs reflects an attacker-controlled redirect_uri parameter from GET /auth/authorize into yamcs-core/src/main/resources/auth/templates/authorize.html without adequate HTML escaping by…
When was CVE-2026-55549 disclosed?
CVE-2026-55549 was first published in the National Vulnerability Database on August 28, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-55549 actively exploited?
CVE-2026-55549 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 71.1% of all scored CVEs.
What is the CVSS score of CVE-2026-55549?
CVE-2026-55549 has a CVSS v3 base score of 6.5 (NVD). The EG score is currently aggregating — additional source signals are being incorporated as they become available..
How do I remediate CVE-2026-55549?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-55549, 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-2026-55549
Is Your Infrastructure Affected by CVE-2026-55549?
EchelonGraph automatically scans your cloud infrastructure and maps CVE exposure using blast radius analysis.