CVE-2026-55759 Vulnerability Analysis & Exploit Details

CVE-2026-55759 Vulnerability Summary

CVE-2026-55759: Rocket.Chat is an open-source, secure, fully customizable communications platform. Prior to 8.5.1, 8.4.4, 8.3.6, 8.2.6, 8.1.6, 8.0.7, and 7.10.13, Rocket.Chat's Apple Sign-In handler verifies JWT signatures but skips claims validation. Any Apple-signed JWT with a non-empty iss is accepted regardless of aud, exp, nbf, or nonce. An attacker who obtains a target user's Apple identity token (from server logs, an intercepted sign-in flow, or another application sharing the same Apple developer team) can replay it to authenticate as that user, with no expiration on the replay window. This vulnerability is fixed in 8.5.1, 8.4.4, 8.3.6, 8.2.6, 8.1.6, 8.0.7, and 7.10.13.

CVE-2026-55759 References

External References

• https://github.com/RocketChat/Rocket.Chat/security/advisories/GHSA-c75c-5hc7-j4vp

CWE Common Weakness Enumeration

CAPEC Common Attack Pattern Enumeration and Classification

• Session Sidejacking CAPEC-102 Session sidejacking takes advantage of an unencrypted communication channel between a victim and target system. The attacker sniffs traffic on a network looking for session tokens in unencrypted traffic. Once a session token is captured, the attacker performs malicious actions by using the stolen token with the targeted application to impersonate the victim. This attack is a specific method of session hijacking, which is exploiting a valid session token to gain unauthorized access to a target system or information. Other methods to perform a session hijacking are session fixation, cross-site scripting, or compromising a user or server machine and stealing the session token.
• Kerberoasting CAPEC-509 Through the exploitation of how service accounts leverage Kerberos authentication with Service Principal Names (SPNs), the adversary obtains and subsequently cracks the hashed credentials of a service account target to exploit its privileges. The Kerberos authentication protocol centers around a ticketing system which is used to request/grant access to services and to then access the requested services. As an authenticated user, the adversary may request Active Directory and obtain a service ticket with portions encrypted via RC4 with the private key of the authenticated account. By extracting the local ticket and saving it disk, the adversary can brute force the hashed value to reveal the target account credentials.
• Remote Services with Stolen Credentials CAPEC-555 This pattern of attack involves an adversary that uses stolen credentials to leverage remote services such as RDP, telnet, SSH, and VNC to log into a system. Once access is gained, any number of malicious activities could be performed.
• Windows Admin Shares with Stolen Credentials CAPEC-561 An adversary guesses or obtains (i.e. steals or purchases) legitimate Windows administrator credentials (e.g. userID/password) to access Windows Admin Shares on a local machine or within a Windows domain.
• Reusing Session IDs (aka Session Replay) CAPEC-60 This attack targets the reuse of valid session ID to spoof the target system in order to gain privileges. The attacker tries to reuse a stolen session ID used previously during a transaction to perform spoofing and session hijacking. Another name for this type of attack is Session Replay.
• Use of Captured Hashes (Pass The Hash) CAPEC-644 An adversary obtains (i.e. steals or purchases) legitimate Windows domain credential hash values to access systems within the domain that leverage the Lan Man (LM) and/or NT Lan Man (NTLM) authentication protocols.
• Use of Captured Tickets (Pass The Ticket) CAPEC-645 An adversary uses stolen Kerberos tickets to access systems/resources that leverage the Kerberos authentication protocol. The Kerberos authentication protocol centers around a ticketing system which is used to request/grant access to services and to then access the requested services. An adversary can obtain any one of these tickets (e.g. Service Ticket, Ticket Granting Ticket, Silver Ticket, or Golden Ticket) to authenticate to a system/resource without needing the account's credentials. Depending on the ticket obtained, the adversary may be able to access a particular resource or generate TGTs for any account within an Active Directory Domain.
• Use of Known Kerberos Credentials CAPEC-652 An adversary obtains (i.e. steals or purchases) legitimate Kerberos credentials (e.g. Kerberos service account userID/password or Kerberos Tickets) with the goal of achieving authenticated access to additional systems, applications, or services within the domain.
• Browser in the Middle (BiTM) CAPEC-701 An adversary exploits the inherent functionalities of a web browser, in order to establish an unnoticed remote desktop connection in the victim's browser to the adversary's system. The adversary must deploy a web client with a remote desktop session that the victim can access.
• Adversary in the Middle (AiTM) CAPEC-94 An adversary targets the communication between two components (typically client and server), in order to alter or obtain data from transactions. A general approach entails the adversary placing themself within the communication channel between the two components.

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