CVE-2026-39410 is a medium-severity vulnerability affecting the Hono web application framework, which supports any JavaScript runtime. This vulnerability allows cookie prefix protections to be bypassed due to discrepancies between browser cookie parsing and the parse() handling. Specifically, cookie names that are treated as distinct by the browser can be normalized to the same key by parse(), enabling attacker-controlled cookies to override legitimate ones. This vulnerability has been addressed in version 4.12.12, released on April 8, 2026.
The CVSS score for this vulnerability is 4.8, indicating a medium severity level. Organizations should be aware that the attack vector is network-based, and although the attack complexity is high, it still presents a risk to applications utilizing Hono prior to the patched version. Risk to organizations includes the potential for unauthorized manipulation of cookies, leading to session hijacking or data leakage.
Given the nature of this vulnerability, organizations using affected versions are advised to prioritize patching immediately. The fix provided in version 4.12.12 should be applied as soon as possible to mitigate any potential risks associated with cookie handling.
For further information, please refer to the official release notes and advisories. It is imperative for security teams to stay informed about vulnerabilities that could impact their software supply chain.
Vulnerability Details
The Hono web application framework has identified a vulnerability related to cookie handling. The official description states that prior to version 4.12.12, a discrepancy between browser cookie parsing and parse() functions allows for cookie prefix protections to be bypassed. This issue can lead to potential unauthorized access to user sessions or data.
This vulnerability is classified under CWE-20 (Improper Input Validation), indicating that the application does not properly validate inputs, allowing attackers to manipulate cookie behavior.
Technical Analysis
The root cause of this vulnerability lies in the handling of cookie names. Due to normalization in the parse() function, cookies that should be treated as distinct can inadvertently override legitimate cookies. This presents a critical risk in environments where cookie-based authentication is employed.
The attack vector is network-based, meaning that an attacker with access to the same network can exploit this vulnerability without requiring physical access to the target system. The attack complexity is rated as high, indicating that successful exploitation may require specific conditions or knowledge.
No user interaction is necessary for an attack to succeed, which increases the potential for exploitation. The confidentiality and integrity impacts are rated low, suggesting that while attacker-controlled cookies can override legitimate ones, the overall impact on availability is none.
Risk & Impact Analysis
Organizations utilizing the Hono framework are at risk of session hijacking or cookie manipulation, which can lead to unauthorized access to sensitive information. The potential blast radius of this vulnerability is significant, particularly for applications handling sensitive user data.
The urgency for remediation is medium, given the exploitability status. While no known exploits are currently available, organizations should address this vulnerability in their patch cycle to prevent future risks. Security teams must assess their exposure and prioritize updates accordingly.
Signal | Status |
|---|---|
Known Exploit | No |
Public PoC | No |
Actively Exploited | No |
Ransomware Use | No |
Affected Versions
The affected versions of Hono are all versions prior to 4.12.12. Organizations should ensure they are running the latest version to avoid exposure to this vulnerability.
Mitigation & Remediation
To mitigate this vulnerability, organizations should upgrade to Hono version 4.12.12 or later. If immediate patching is not possible, consider implementing configuration hardening measures to limit cookie exposure and monitor application behavior for any anomalies.
Organizations can validate remediation effectiveness through penetration testing that specifically tests cookie handling mechanisms.
Detection Guidance
Organizations should monitor logs for unusual cookie behavior and implement network signatures that detect attempts to manipulate cookie values. Behavioral anomalies in user sessions should also be flagged for investigation.
AppSecure Threat Intelligence Insight
The long-term significance of CVE-2026-39410 lies in its indication of how cookie handling flaws can lead to substantial security risks in web applications. Security teams should learn from this vulnerability to enhance input validation and cookie management practices.
This incident reflects a broader trend of vulnerabilities arising from improper input validation, emphasizing the need for robust security measures in software development. Organizations are encouraged to adopt a proactive stance in vulnerability management.
For further insights on improving cookie security, organizations can refer to our comprehensive guide on security testing best practices and implement continuous assessment strategies.
Engaging in comprehensive vulnerability management programs can significantly lower the risk of similar vulnerabilities in the future.
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
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