CVE-2018-15811
DotNetNuke (DNN) Inadequate Encryption Strength Vulnerability
Description
CVE-2018-15811 is a HIGH severity vulnerability in DotNetNuke (DNN) versions 9.2 through 9.2.1, classified under CWE-326 (Inadequate Encryption Strength). The flaw arises from the use of a weak encryption algorithm to protect input parameters, allowing remote attackers to decrypt sensitive data without authentication. With a CVSS 3.1 score of 7.5, this vulnerability enables attackers to extract confidential information from DNN installations. CISA added CVE-2018-15811 to its Known Exploited Vulnerabilities catalog on November 3, 2021. The EPSS score of 0.91142 (99.64th percentile) indicates a very high probability of exploitation. Note that CVE-2018-18325 was issued for an incomplete fix of this vulnerability.
KEV Information
CVSS Score
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:NOpen in CalculatorAffected Products
| Vendor | Product | Version |
|---|---|---|
| dnnsoftware | dotnetnuke | >= 9.2, <= 9.2.1 |
Multiple CVSS Assessments
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
References
- http://packetstormsecurity.com/files/157080/DotNetNuke-Cookie-Deserialization-Remote-Code-Execution.html(Exploit, Third Party Advisory, VDB Entry)
- https://github.com/dnnsoftware/Dnn.Platform/releases(Release Notes)
- https://www.dnnsoftware.com/community/security/security-center(Vendor Advisory)
- https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2018-15811(US Government Resource)
Weakness Type
CWE-326: Inadequate Encryption Strength
Inadequate Encryption Strength occurs when software uses a cryptographic algorithm or key length that is insufficient to protect data from being decrypted by an attacker. While the software does employ encryption, the chosen algorithm or implementation is weak enough that a motivated attacker can break it using known cryptanalytic techniques, brute-force attacks, or by exploiting structural weaknesses in the algorithm itself. This weakness is particularly dangerous when it protects authentication tokens, session data, or other security-critical parameters because breaking the encryption grants the attacker direct access to protected functionality.
In the context of CVE-2018-15811, DotNetNuke versions 9.2 through 9.2.1 used a weak encryption algorithm to protect input parameters passed between the client and server. These parameters include security-sensitive values such as authentication cookies and serialized objects. Because the encryption was inadequate, attackers could reverse-engineer the encryption scheme and craft malicious encrypted payloads. This weakness was later chained with cookie deserialization attacks to achieve remote code execution on affected DNN installations.
Learn more: CWE-326 — Inadequate Encryption Strength
Impact Analysis
CVE-2018-15811 carries a CVSS 3.1 base score of 7.5 (HIGH) with network-exploitable attack characteristics.
Confidentiality (High): The weak encryption algorithm allows remote attackers to decrypt protected input parameters without authentication. This exposes security-critical data including authentication tokens, session identifiers, and serialized objects. Attackers who successfully break the encryption can access any data protected by the weak algorithm, potentially including user credentials, administrative tokens, and internal application state.
Integrity (None): The CVSS vector indicates no direct integrity impact from the vulnerability itself. However, the decrypted information can be leveraged in subsequent attacks, particularly cookie deserialization exploits that achieve full remote code execution, which would then have severe integrity consequences.
Availability (None): The vulnerability does not directly impact system availability. The primary risk is information disclosure through cryptographic weakness, though downstream exploitation chains can lead to complete system compromise.
Scope (Unchanged): The vulnerability affects only the DNN application context. However, given that DNN is a web content management system often hosting sensitive organizational data, the confidentiality impact can be significant. The EPSS score of 0.91142 (99.64th percentile) places this in the top 0.4% of all CVEs for exploitation probability, reflecting the availability of public exploit code that chains this weakness with deserialization attacks.
Exploit Maturity
Active Exploitation: CVE-2018-15811 is actively exploited in the wild. CISA added this vulnerability to the Known Exploited Vulnerabilities (KEV) catalog on November 3, 2021, with a mandatory remediation deadline of May 3, 2022 for federal agencies.
Public Exploits: A detailed exploit for DotNetNuke cookie deserialization leading to remote code execution is publicly available on Packet Storm Security. This exploit chains the weak encryption vulnerability with unsafe deserialization to achieve full remote code execution on affected DNN installations.
Exploit Chain: The typical attack flow involves first exploiting the weak encryption (CVE-2018-15811) to understand how DNN encrypts cookie values, then crafting a malicious serialized object, encrypting it using the weak algorithm, and submitting it as a cookie. When DNN decrypts and deserializes the cookie, arbitrary code is executed on the server.
EPSS Context: The EPSS score of 0.91142 (99.64th percentile) places this vulnerability in the top 0.4% of all CVEs for exploitation probability. This exceptionally high score reflects the public availability of reliable exploit code and confirmed active exploitation.
Related Vulnerability: CVE-2018-18325 addresses an incomplete fix for this same issue in DNN versions through 9.2.2. Organizations must ensure they have patched both vulnerabilities.
Remediation
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Upgrade DotNetNuke to version 9.2.2 or later immediately. The patch addresses the weak encryption algorithm used to protect input parameters. Download the latest version from the DNN Platform releases on GitHub.
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Verify the fix for CVE-2018-18325 is also applied. The initial patch for CVE-2018-15811 was incomplete, and CVE-2018-18325 was issued for the remaining weakness. Ensure your DNN installation is updated to at least version 9.3.0 or later to address both vulnerabilities completely.
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Rotate all encryption keys and authentication tokens. After upgrading, regenerate the machine key and any encryption keys used by the DNN installation. Old tokens encrypted with the weak algorithm may still be valid and could be exploited if not invalidated.
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Audit server logs for indicators of compromise. Review IIS logs and DNN event logs for suspicious cookie values, unusual deserialization errors, or evidence of remote code execution. Look for unexpected process creation, file writes, or network connections originating from the DNN application pool identity.
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Implement a web application firewall (WAF). Deploy WAF rules to inspect and block suspicious cookie payloads that may contain serialized .NET objects. This provides defense-in-depth while ensuring all DNN instances are fully patched.
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Restrict network access to DNN administrative interfaces. Limit access to DNN admin panels to trusted IP ranges and require multi-factor authentication for all administrative accounts to reduce the attack surface.
Technical Details
CVE-2018-15811 is a cryptographic weakness in DotNetNuke (DNN) versions 9.2 through 9.2.1. DNN uses encryption to protect input parameters that are passed between the client browser and the server, including cookie values that contain serialized .NET objects. The vulnerability exists because DNN employed a weak encryption algorithm that could be reverse-engineered by attackers.
The CVSS vector (AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N) reflects that the vulnerability is exploitable remotely over the network with no authentication required and no user interaction needed. The attack complexity is low because the weak encryption algorithm can be broken using readily available tools and techniques.
The practical impact of this vulnerability extends beyond simple information disclosure. DNN uses encrypted cookies to store serialized .NET objects, and the platform deserializes these objects on the server side. By breaking the weak encryption, an attacker can craft a malicious serialized object, encrypt it using the same weak algorithm, and submit it as a cookie. When DNN decrypts and deserializes this crafted cookie, it triggers unsafe deserialization, leading to remote code execution on the server.
The public exploit published on Packet Storm Security demonstrates this complete attack chain: breaking the encryption, crafting a malicious serialized payload using tools like ysoserial.net, and achieving remote code execution. The exploit is reliable and does not require any authentication, making it accessible to a wide range of threat actors.
The initial fix released by DNN was incomplete, leading to CVE-2018-18325 being assigned for the residual weakness in versions through 9.2.2. Organizations must ensure they apply patches for both CVEs to fully remediate this vulnerability.
Frequently Asked Questions
Is CVE-2018-15811 being actively exploited?
Yes, CVE-2018-15811 is actively exploited in the wild. CISA added it to the Known Exploited Vulnerabilities catalog on November 3, 2021, confirming active exploitation. Public exploit code is available that chains this weak encryption vulnerability with cookie deserialization to achieve remote code execution on DotNetNuke installations.
What products are affected by CVE-2018-15811?
DotNetNuke (DNN) versions 9.2 through 9.2.1 are affected. DNN is an open-source web content management system built on the Microsoft .NET framework. Any website running these versions is vulnerable to the weak encryption attack that can lead to remote code execution through the deserialization exploit chain.
How do I fix CVE-2018-15811?
Upgrade DotNetNuke to version 9.3.0 or later to address both CVE-2018-15811 and the related CVE-2018-18325 (which fixed an incomplete patch). After upgrading, rotate all encryption keys and machine keys, and audit server logs for signs of prior exploitation. The latest DNN releases are available on the DNN Platform GitHub repository.
How severe is CVE-2018-15811?
CVE-2018-15811 is rated HIGH with a CVSS score of 7.5. While the vulnerability itself is classified as an information disclosure issue through weak encryption, its real-world impact is significantly amplified because the disclosed information enables a remote code execution attack through cookie deserialization. The EPSS score of 0.91142 (99.64th percentile) reflects the extremely high exploitation probability, placing it in the top 0.4% of all known vulnerabilities.
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