CVE-2016-7855
Adobe Flash Player Use-After-Free Vulnerability
Description
CVE-2016-7855 is a high-severity vulnerability affecting Adobe Flash Player, carrying a CVSS 3.1 base score of 8.8. Classified under CWE-416 (Use After Free), this vulnerability allows an attacker to achieve remote code execution on affected systems by exploiting improper handling in the software's processing logic. This CVE has been added to CISA's Known Exploited Vulnerabilities (KEV) catalog on 2022-03-03, confirming active exploitation in the wild with a federal remediation deadline of 2022-03-24. With an EPSS score of 43.2% (97.44th percentile), the probability of exploitation activity is notable compared to other known vulnerabilities.
KEV Information
CVSS Score
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:HOpen in CalculatorAffected Products
| Vendor | Product | Version |
|---|---|---|
| adobe | flash player | <= 23.0.0.185; <= 11.2.202.637 |
| redhat | enterprise linux desktop | 5.0; 6.0 |
| redhat | enterprise linux server | 5.0; 6.0 |
| redhat | enterprise linux workstation | 5.0; 6.0 |
Multiple CVSS Assessments
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
References
- http://rhn.redhat.com/errata/RHSA-2016-2119.html(Third Party Advisory)
- http://www.securityfocus.com/bid/93861(Third Party Advisory, VDB Entry)
- http://www.securitytracker.com/id/1037111(Third Party Advisory, VDB Entry)
- https://docs.microsoft.com/en-us/security-updates/securitybulletins/2016/ms16-128(Patch, Vendor Advisory)
- https://helpx.adobe.com/security/products/flash-player/apsb16-36.html(Patch, Vendor Advisory)
- https://security.gentoo.org/glsa/201610-10(Third Party Advisory)
- https://security.googleblog.com/2016/10/disclosing-vulnerabilities-to-protect.html(Third Party Advisory)
- https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2016-7855(US Government Resource)
Weakness Type
CWE-416: Use After Free
Use After Free (UAF) is a vulnerability that occurs when software continues to use a pointer after the memory it references has been freed. Once memory is freed, it may be reallocated for other purposes. If the dangling pointer is subsequently dereferenced, the program may read or write to memory now used for different data structures, leading to data corruption, information disclosure, or code execution. Use-after-free vulnerabilities are particularly prevalent in complex applications with manual memory management, including browsers, document parsers, and operating system kernels. This category of weakness is particularly relevant in the context of Adobe Flash Player, where the security boundary between user-supplied input and system-level processing must be carefully maintained to prevent exploitation. Understanding the underlying weakness mechanism is essential for both assessing the risk posed by CVE-2016-7855 and implementing effective countermeasures.
In the specific case of CVE-2016-7855, the use after free manifests within Adobe Flash Player's processing components. Use-after-free vulnerabilities are highly exploitable and consistently rank among the most dangerous software weaknesses. Attackers leverage heap manipulation techniques to control what data occupies the freed memory when the dangling pointer is dereferenced. By placing attacker-controlled objects (containing function pointers or vtables) in the freed space, code execution is achieved when the stale pointer is used. Browsers are frequent targets due to complex JavaScript/DOM interactions that create race conditions and memory management errors. UAF bugs have enabled numerous browser-based attacks, privilege escalation exploits, and malware campaigns. The remediation strategy for this weakness class involves implement strict ownership semantics and lifecycle management for allocated memory. use smart pointers (std::unique_ptr, std::shared_ptr in c++) that automatically manage memory and prevent dangling r. Organizations relying on Adobe Flash Player should prioritize patching this vulnerability, as the weakness class it belongs to is a well-understood and frequently targeted attack surface.
Learn more: CWE-416 — Use After Free
Impact Analysis
CVE-2016-7855 carries a CVSS 3.1 base score of 8.8 (HIGH), reflecting its significant potential for harm across multiple impact dimensions.
Confidentiality (HIGH): An attacker who successfully exploits this vulnerability gains the ability to access sensitive data stored on or processed by the affected system. This includes configuration files, credentials, cryptographic keys, and potentially proprietary or regulated data. In environments where the compromised system handles personally identifiable information (PII) or financial records, the confidentiality breach could trigger regulatory compliance violations and significant reputational damage.
Integrity (HIGH): Successful exploitation permits the attacker to modify data, install backdoors, alter system configurations, or inject malicious code. This level of integrity compromise means the attacker can manipulate the system to serve their objectives, whether that involves deploying ransomware, establishing persistent access, or pivoting to other systems within the network. The trustworthiness of the affected system is completely undermined once integrity is compromised at this level.
Availability (HIGH): The vulnerability can be leveraged to completely disrupt the availability of the affected service or device. An attacker can force a system crash, trigger a reload, or render the device inoperable, causing significant operational disruption. For critical infrastructure components like network devices or security appliances, even brief availability outages can have cascading effects across the organization.
Scope (Unchanged): The scope is Unchanged, meaning the impact of the vulnerability is limited to the affected component itself. While the consequences within that component can be severe, the exploitation does not directly extend to other systems or security domains.
The EPSS score of 43.2% (97.44th percentile) indicates notable exploitation probability, reflecting the real-world interest threat actors have shown in this vulnerability.
Exploit Maturity
CVE-2016-7855 has confirmed active exploitation in the wild, as evidenced by its inclusion in CISA's Known Exploited Vulnerabilities catalog.
Active Exploitation: This vulnerability was added to the CISA KEV catalog on 2022-03-03, confirming that threat actors have actively exploited it in real-world attacks against organizations. The KEV listing represents a high-confidence indicator of exploitation, as CISA requires evidence of active exploitation before adding vulnerabilities to this catalog. Federal agencies were required to remediate this vulnerability by the deadline of 2022-03-24.
Ransomware Association: According to the CISA KEV catalog, this vulnerability has not been specifically linked to known ransomware campaigns at this time. However, the confirmed active exploitation means that threat actors are leveraging this vulnerability for other objectives such as espionage, data theft, or establishing persistent footholds within target networks.
Public Exploits: While specific public exploit code may not be widely cataloged in standard databases, the KEV listing confirms that exploitation is occurring in the wild. Threat actors may be using privately developed exploit tools or leveraging the vulnerability through commercial exploit frameworks.
EPSS Score: The EPSS score of 43.2% (97.44th percentile) indicates moderate-to-notable exploitation likelihood, consistent with observed real-world exploitation activity.
KEV Remediation Deadline: 2022-03-24. Federal agencies under BOD 22-01 were required to remediate by this date, and all organizations are strongly encouraged to treat this deadline as a benchmark for their own patch management timelines.
Remediation
- The impacted product is end-of-life and should be disconnected if still in use. This is the primary remediation action specified in the CISA KEV catalog. Since the affected product has reached end-of-life status, no further security patches will be provided by the vendor. Continued use of this software exposes the organization to unpatched vulnerabilities with no prospect of vendor remediation.
- Remove or replace the affected software with a supported alternative. Identify a currently maintained product that provides equivalent functionality and migrate all dependent workflows. Ensure the replacement product is kept up to date with the latest security patches from its vendor.
- If immediate removal is not possible, isolate the affected system. Place the affected system in a network segment with strict access controls, limiting both inbound and outbound network traffic to only essential communications. This reduces the attack surface while migration planning is underway.
- Implement compensating security controls around the affected system. Deploy network-level intrusion detection and prevention systems (IDS/IPS) to monitor traffic to and from the affected system. Apply web application firewalls or protocol-specific filters where applicable to detect and block exploitation attempts.
- Monitor for indicators of compromise (IOCs) associated with this vulnerability. Review security logs for evidence of exploitation attempts or successful compromise. Establish alerts for anomalous behavior originating from or targeting the affected system.
- Conduct a risk assessment to prioritize the migration timeline. Document the business risk of continued use of the end-of-life product, including regulatory and compliance implications. Use this assessment to justify and accelerate the transition to a supported platform.
Technical Details
CVE-2016-7855 is a high-severity vulnerability in Adobe Flash Player that enables arbitrary code execution through exploitation of use after free. The vulnerability exists in the way Adobe Flash Player handles certain network-facing operations, where insufficient validation or improper processing of incoming requests or data allows an attacker to trigger the vulnerable condition.
The attack vector is Network (AV:N), meaning exploitation can occur remotely over the network without physical access. The attack complexity is low complexity (AC:L), indicating that reliable exploitation does not require specialized conditions or preparation beyond having access to the attack vector. The vulnerability requires no privileges (PR:N) and user interaction (such as opening a malicious file or visiting a crafted webpage) (UI:R).
The scope is Unchanged (S:U), indicating the impact is contained within the vulnerable component's own security scope. The combined impact ratings of HIGH/HIGH/HIGH for Confidentiality/Integrity/Availability reflect the high-severity nature of this flaw. The root cause — use after free — is a well-documented weakness class with established exploitation techniques, making this vulnerability a reliable target for attackers who have network access or the ability to deliver malicious input to the affected component. Affected products include: adobe flash player (versions: <= 23.0.0.185; <= 11.2.202.637); redhat enterprise linux desktop (versions: 5.0; 6.0); redhat enterprise linux server (versions: 5.0; 6.0); redhat enterprise linux workstation (versions: 5.0; 6.0).
Frequently Asked Questions
Is CVE-2016-7855 actively exploited?
Yes, CVE-2016-7855 is confirmed to be actively exploited in the wild. It was added to CISA's Known Exploited Vulnerabilities (KEV) catalog on 2022-03-03, which requires evidence of active exploitation before a vulnerability can be listed. While not specifically linked to ransomware campaigns at this time, the confirmed exploitation means threat actors are leveraging it for various malicious objectives. The EPSS score of 43.2% (97.44th percentile) further underscores the high likelihood of ongoing exploitation activity. Organizations should treat this as an urgent security issue requiring immediate attention.
What products are affected by CVE-2016-7855?
CVE-2016-7855 affects Adobe Flash Player. Specifically, the following product versions have been identified as vulnerable: adobe flash player (versions: <= 23.0.0.185; <= 11.2.202.637); redhat enterprise linux desktop (versions: 5.0; 6.0); redhat enterprise linux server (versions: 5.0; 6.0); redhat enterprise linux workstation (versions: 5.0; 6.0). Organizations should conduct a thorough inventory of their environments to identify all deployments of the affected software. Both production systems and development or staging environments should be included in this assessment, as any unpatched instance represents a potential entry point for attackers.
How do I fix CVE-2016-7855?
Since the affected product is end-of-life, the primary remediation is to discontinue use of the software and migrate to a supported alternative. There are no further security patches available from the vendor. Until migration is complete, isolate affected systems from the network, implement strict access controls, and monitor for signs of exploitation. After remediation, verify that the patch was successfully applied and review system logs for any indicators of prior compromise, as unpatched systems may have been targeted before the fix was deployed.
How severe is CVE-2016-7855?
CVE-2016-7855 is rated HIGH with a CVSS 3.1 base score of 8.8. The vulnerability can be exploited remotely over the network, with low attack complexity, and requires user interaction to trigger. The impact across confidentiality, integrity, and availability is all rated High, meaning successful exploitation can result in complete system compromise. Its inclusion in the CISA KEV catalog with a remediation deadline of 2022-03-24 confirms the real-world severity. The EPSS score of 43.2% places it in the 97.44th percentile for exploitation likelihood.
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