CVE-2015-8542

CVE-2015-8542 is a high-severity vulnerability in Open-xchange Ox Guard with a CVSS 3.x base score of 8.8. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-320.

Key facts

Description

An issue was discovered in Open-Xchange Guard before 2.2.0-rev8. The "getprivkeybyid" API call is used to download a PGP Private Key for a specific user after providing authentication credentials. Clients provide the "id" and "cid" parameter to specify the current user by its user- and context-ID. The "auth" parameter contains a hashed password string which gets created by the client by asking the user to enter his or her OX Guard password. This parameter is used as single point of authentication when accessing PGP Private Keys. In case a user has set the same password as another user, it is possible to download another user's PGP Private Key by iterating the "id" and "cid" parameters. This kind of attack would also be able by brute-forcing login credentials, but since the "id" and "cid" parameters are sequential they are much easier to predict than a user's login name. At the same time, there are some obvious insecure standard passwords that are widely used. A attacker could send the hashed representation of typically weak passwords and randomly fetch Private Key of matching accounts. The attack can be executed by both internal users and "guests" which use the external mail reader.

Frequently asked questions

What is CVE-2015-8542?
An issue was discovered in Open-Xchange Guard before 2.2.0-rev8. The "getprivkeybyid" API call is used to download a PGP Private Key for a specific user after providing authentication credentials. Clients provide the "id" and "cid" parameter to specify the current user by its user- and context-ID. The "auth" parameter contains a hashed password string which gets created by the client by asking the user to enter his or her OX Guard password. This parameter is used as single point of authentication when accessing PGP Private Keys. In case a user has set the same password as another user, it is possible to download another user's PGP Private Key by iterating the "id" and "cid" parameters. This kind of attack would also be able by brute-forcing login credentials, but since the "id" and "cid" parameters are sequential they are much easier to predict than a user's login name. At the same time, there are some obvious insecure standard passwords that are widely used. A attacker could send the hashed representation of typically weak passwords and randomly fetch Private Key of matching accounts. The attack can be executed by both internal users and "guests" which use the external mail reader.
How severe is CVE-2015-8542?
CVE-2015-8542 has a CVSS 3.x base score of 8.8, rated high severity. It is exploitable over network with low attack complexity, requires low privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.
Is CVE-2015-8542 being actively exploited?
It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 2% (80th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2015-8542?
CVE-2015-8542 affects Open-xchange Ox Guard. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2015-8542?
Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
When was CVE-2015-8542 published?
CVE-2015-8542 was published on 2016-12-15 and last updated on 2026-06-17.

References

Affected products (1)

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