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CVE-2016-4028

24
FAUCET Score

CVE-2016-4028 describes a padding oracle vulnerability in Open-Xchange OX Guard versions prior to 2.4.0-rev8. The OX Guard API's differing error responses to invalid encryption padding, when combined with AES-CBC, allows attackers to deduce the correct padding. This vulnerability enables brute-force attacks on guest authentication tokens, potentially exposing user credentials. The vulnerability has a CVSS v3 score of 7.5 (HIGH), indicating a high impact on confidentiality, integrity, and availability, with a network attack vector and high attack complexity. Successful exploitation requires a logged-in guest user and knowledge of their "OxReaderID" cookie and "auth" parameter. There is no evidence of active exploitation, nor are there publicly available exploit modules in Metasploit, Nuclei, or ExploitDB. Community discussion and media coverage for this CVE are minimal, suggesting low public awareness or interest.

Impacted Technologies

VendorProductVersion(s)CPE
<= 2.4.0CPE matchmatch criteria
cpe:2.3:a:open-xchange:ox_guard:*:rev7:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 3.0

7.5HIGH

CVSS:3.0/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H

Attack Vector
NETWORK
Attack Complexity
HIGH
Privileges Required
LOW
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
HIGH
Integrity Impact
HIGH
Availability Impact
HIGH
Exploitability Score
1.6
Impact Score
5.9
CvssVersion
3.0

Exploit Intelligence

EPSS Score
0.71%
Probability of exploitation in next 30 days
EPSS Percentile
49.7%
Percentile rank of EPSS score among Peer Group
As of 2026-07-26
Model: v2026.06.15
This CVE's current EPSS score of 0.0071 is in the 46th percentile among its peer group of 1,162 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.1 Reddit, 0.2 Bluesky, 0.1 Mastodon, and 0.2 GitHub mentions.

Media Mentions

No media coverage found for this CVE.

The average CVE in this peer group has 0.1 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Remediation records are not available for this CVE.

References

securityfocus.com / archive/1/538732/100/0/threaded
securitytracker.com / id/1036154
Third Party AdvisoryVDB Entry