Xlight FTP Server before 3.9.5 contains a pre-authentication heap buffer overflow vulnerability that allows remote unauthenticated attackers to write past the end of a heap buffer by sending a malformed SSH client identification string. A logic error in the recv loop's termination condition uses an incorrect OR operator where an AND operator is required, enabling exploitation on any SSH or SFTP connection before authentication occurs.
CVE-2026-67191
CRITICALPre-NVD 9.89.8
EchelonGraph scoreLOW confidence
This critical-severity CVE scores 9.8 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
9.8EG
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
- High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: —CVSS: 9.8Exploit: None knownExposed: 0
No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.
- CVSS v3
- 9.8
- EG Score
- 9.8(low)
- EG Risk
- 44(Track)EG Risk 44/100SSVC: 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 computedSeverity98% × 45%Exploitation0% × 40%Automatability0% × 15%Action: Routine — remediate on your standard cadence. - EPSS PROB
- —
- EPSS %ILE
- —
- KEV
- Not listed
Published
July 29, 2026
Last Modified
July 29, 2026
Advisory Details (2)
Auto-updated Jul 29, 2026No patch confirmed yet.
generic
Xlight FTP Server < 3.9.5 Pre-Auth Heap Buffer Overflow via SSH Parser | Advisories | VulnCheck
https://www.vulncheck.com/advisories/xlight-ftp-server-pre-auth-heap-buffer-overflow-via-ssh-parserWeakness Classification(1)
MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.
Data Freshness Timeline
(refreshed 5× in last 7d / 5× 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.
- 2026-07-29 17:26 UTCEG score recompute
- 2026-07-29 16:38 UTCEG score recompute
- 2026-07-29 16:23 UTCEG score recompute
- 2026-07-29 16:07 UTCEG score recompute
- 2026-07-29 16:07 UTCMITRE cvelistV5first tracked
Related CVEs(same CWE)
Same CWE
10 shownCWE-122
- CVE-2016-9603NVD 5.5EG 9.9EPSS p90CRITICAL
- CVE-2006-10003EG 9.8CRITICAL
- CVE-2006-10002NVD 7.5EG 9.8CRITICAL
- CVE-2019-18323EG 9.8CRITICAL
- CVE-2019-18296EG 9.8EPSS p91CRITICAL
- CVE-2019-18295EG 9.8EPSS p91CRITICAL
- CVE-2019-18293EG 9.8EPSS p91CRITICAL
- CVE-2019-18289EG 9.8EPSS p91CRITICAL
- CVE-2019-14901EG 9.8EPSS p97CRITICAL
- CVE-2019-14895EG 9.8EPSS p94CRITICAL
Frequently asked(4)
What is CVE-2026-67191?
CVE-2026-67191 is a critical vulnerability published on July 29, 2026. Xlight FTP Server before 3.9.5 contains a pre-authentication heap buffer overflow vulnerability that allows remote unauthenticated attackers to write past the end of a heap buffer by sending a malformed SSH client identification string. A logic error in the recv loop's termination condition uses an…
When was CVE-2026-67191 disclosed?
CVE-2026-67191 was first published in the National Vulnerability Database on July 29, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
What is the CVSS score of CVE-2026-67191?
CVE-2026-67191 has a CVSS v3 base score of 9.8 (NVD). The EG score is currently aggregating — additional source signals are being incorporated as they become available..
How do I remediate CVE-2026-67191?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-67191, 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-2026-67191
Is Your Infrastructure Affected by CVE-2026-67191?
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