CVE-2026-77254 Vulnerability Analysis & Exploit Details

CVE-2026-77254
Vulnerability Scoring

9.1
/10
Critical Risk

As a catastrophic security flaw, CVE-2026-77254 has severe implications, demanding immediate intervention.

Attack Complexity Details

  • Attack Complexity: Low
    Exploits can be performed without significant complexity or special conditions.
  • Attack Vector: Network
    Vulnerability is exploitable over a network without physical access.
  • Privileges Required: None
    No privileges are required for exploitation.
  • Scope: Unchanged
    Exploit remains within the originally vulnerable component.
  • User Interaction: None
    No user interaction is necessary for exploitation.

CVE-2026-77254 Details

Status: Undergoing Analysis

Last updated: 🕕 23 Sep 2026, 18:28 UTC
Originally published on: 🕖 22 Sep 2026, 19:16 UTC

CVSS Release: version 3

CVSS3 Source

security-advisories@github.com

CVSS3 Type

Secondary

CVSS3 Vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N

CVE-2026-77254 Vulnerability Summary

CVE-2026-77254: MCP Atlassian is a Model Context Protocol (MCP) server for Atlassian products (Confluence and Jira). Prior to 0.22.0, requests to the HTTP MCP endpoint without a per-user identity are allowed to reach tool handlers, which then use globally configured Jira or Confluence credentials. A network caller can perform operations with the operator account's permissions unless the deployment has an independent authentication boundary. The advisory traces the vulnerable input and processing flow through streamable-http, UserTokenMiddleware, _get_fetcher, and global credentials, which identify the affected entry points, controls, and code paths. This issue is fixed in version 0.22.0.

Assessing the Risk of CVE-2026-77254

Access Complexity Graph

The exploitability of CVE-2026-77254 depends on two key factors: attack complexity (the level of effort required to execute an exploit) and privileges required (the access level an attacker needs).

Exploitability Analysis for CVE-2026-77254

With low attack complexity and no required privileges, CVE-2026-77254 is an easy target for cybercriminals. Organizations should prioritize immediate mitigation measures to prevent unauthorized access and data breaches.

Understanding AC and PR

A lower complexity and fewer privilege requirements make exploitation easier. Security teams should evaluate these aspects to determine the urgency of mitigation strategies, such as patch management and access control policies.

Attack Complexity (AC) measures the difficulty in executing an exploit. A high AC means that specific conditions must be met, making an attack more challenging, while a low AC means the vulnerability can be exploited with minimal effort.

Privileges Required (PR) determine the level of system access necessary for an attack. Vulnerabilities requiring no privileges are more accessible to attackers, whereas high privilege requirements limit exploitation to authorized users with elevated access.

CVSS Score Breakdown Chart

Above is the CVSS Sub-score Breakdown for CVE-2026-77254, illustrating how Base, Impact, and Exploitability factors combine to form the overall severity rating. A higher sub-score typically indicates a more severe or easier-to-exploit vulnerability.

CIA Impact Analysis

Below is the Impact Analysis for CVE-2026-77254, showing how Confidentiality, Integrity, and Availability might be affected if the vulnerability is exploited. Higher values usually signal greater potential damage.

  • Confidentiality: High
    Exploiting CVE-2026-77254 can result in unauthorized access to sensitive data, severely compromising data privacy.
  • Integrity: High
    CVE-2026-77254 could allow unauthorized modifications to data, potentially affecting system reliability and trust.
  • Availability: None
    CVE-2026-77254 does not impact system availability.

CVE-2026-77254 References

External References

CWE Common Weakness Enumeration

CWE-306

CAPEC Common Attack Pattern Enumeration and Classification

  • Choosing Message Identifier CAPEC-12 This pattern of attack is defined by the selection of messages distributed via multicast or public information channels that are intended for another client by determining the parameter value assigned to that client. This attack allows the adversary to gain access to potentially privileged information, and to possibly perpetrate other attacks through the distribution means by impersonation. If the channel/message being manipulated is an input rather than output mechanism for the system, (such as a command bus), this style of attack could be used to change the adversary's identifier to more a privileged one.
  • Force the System to Reset Values CAPEC-166 An attacker forces the target into a previous state in order to leverage potential weaknesses in the target dependent upon a prior configuration or state-dependent factors. Even in cases where an attacker may not be able to directly control the configuration of the targeted application, they may be able to reset the configuration to a prior state since many applications implement reset functions.
  • Communication Channel Manipulation CAPEC-216 An adversary manipulates a setting or parameter on communications channel in order to compromise its security. This can result in information exposure, insertion/removal of information from the communications stream, and/or potentially system compromise.
  • Using Unpublished Interfaces or Functionality CAPEC-36 An adversary searches for and invokes interfaces or functionality that the target system designers did not intend to be publicly available. If interfaces fail to authenticate requests, the attacker may be able to invoke functionality they are not authorized for.
  • Cross Site Request Forgery CAPEC-62 An attacker crafts malicious web links and distributes them (via web pages, email, etc.), typically in a targeted manner, hoping to induce users to click on the link and execute the malicious action against some third-party application. If successful, the action embedded in the malicious link will be processed and accepted by the targeted application with the users' privilege level. This type of attack leverages the persistence and implicit trust placed in user session cookies by many web applications today. In such an architecture, once the user authenticates to an application and a session cookie is created on the user's system, all following transactions for that session are authenticated using that cookie including potential actions initiated by an attacker and simply "riding" the existing session cookie.

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