CVE-2016-4028

HIGHNVD 7.57.5—
EchelonGraph scoreMEDIUM confidence

Score 7.5 from GitHub Security Advisory (severity: HIGH) published 2022-05-14. NVD baseline CVSS 7.5; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: epss, ghsa, nvd
7.5
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS: 1%CVSS: 7.5Exploit: NoneExposed: 0

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

An issue was discovered in Open-Xchange OX Guard before 2.4.0-rev8. OX Guard uses an authentication token to identify and transfer guest users' credentials. The OX Guard API acts as a padding oracle by responding with different error codes depending on whether the provided token matches the encryption padding. In combination with AES-CBC, this allows attackers to guess the correct padding. Attackers may run brute-forcing attacks on the content of the guest authentication token and discover user credentials. For a practical attack vector, the guest users needs to have logged in, the content of the guest user's "OxReaderID" cookie and the value of the "auth" parameter needs to be known to the attacker.

CVSS v3
7.5
EG Score
7.5(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
Severity75% × 45%
Exploitation1% × 40%
Automatability30% × 15%
Action: Routine — remediate on your standard cadence.
EPSS
49.7%
KEV
Not listed

Published

December 15, 2016

Last Modified

May 6, 2026

References (4)

Data Freshness Timeline

(refreshed 12× in last 7d / 41× 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. 2026-07-23 14:14 UTCEPSS rescore
  2. 2026-07-23 01:23 UTCEG score recompute
  3. 2026-07-22 22:02 UTCEG score recompute
  4. 2026-07-22 14:04 UTCEPSS rescore
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  1. 2026-07-07 13:42 UTCEPSS rescore
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  44. 2026-06-06 13:45 UTCEPSS rescore
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  55. 2026-05-31 00:14 UTCEPSS rescore
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  64. 2026-05-22 21:15 UTCEPSS rescore
  65. 2026-05-22 21:15 UTCEPSS rescore
  66. 2026-05-22 17:37 UTCEG score recompute
  67. 2026-05-22 17:36 UTCGHSA enrichment
  68. 2026-05-20 11:21 UTCEPSS rescore
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  71. 2026-05-18 21:30 UTCEPSS rescore
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Frequently asked(5)

What is CVE-2016-4028?
CVE-2016-4028 is a high vulnerability published on December 15, 2016. An issue was discovered in Open-Xchange OX Guard before 2.4.0-rev8. OX Guard uses an authentication token to identify and transfer guest users' credentials. The OX Guard API acts as a padding oracle by responding with different error codes depending on whether the provided token matches the…
When was CVE-2016-4028 disclosed?
CVE-2016-4028 was first published in the National Vulnerability Database on December 15, 2016, with the most recent update on May 6, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2016-4028 actively exploited?
CVE-2016-4028 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 49.7% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.
What is the CVSS score of CVE-2016-4028?
CVE-2016-4028 has a CVSS v3 base score of 7.5 (NVD).
How do I remediate CVE-2016-4028?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2016-4028, 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.

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