CVE-2026-77255 Vulnerability Analysis & Exploit Details

CVE-2026-77255
Vulnerability Scoring

8.6
/10
Severe Risk

Cybersecurity professionals consider CVE-2026-77255 an immediate threat requiring urgent mitigation.

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: Changed
    Successful exploitation can impact components beyond the vulnerable component.
  • User Interaction: None
    No user interaction is necessary for exploitation.

CVE-2026-77255 Details

Status: Analyzed

Last updated: 🕜 29 Sep 2026, 13:41 UTC
Originally published on: 🕖 22 Sep 2026, 19:16 UTC

Time between publication and last update: 6 days

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:C/C:H/I:N/A:N

CVE-2026-77255 Vulnerability Summary

CVE-2026-77255: MCP Atlassian is a Model Context Protocol (MCP) server for Atlassian products (Confluence and Jira). Prior to 0.22.0, the Jira update_issue attachments argument is converted into local paths and routed to the attachment upload implementation without workspace validation. A caller can make the MCP server read arbitrary local files and attach them to a Jira issue, using the server as a confused deputy to exfiltrate the contents. The advisory traces the vulnerable input and processing flow through jira update_issue, attachments, upload_attachment, and file_path, which identify the affected entry points, controls, and code paths. This issue is fixed in version 0.22.0.

Assessing the Risk of CVE-2026-77255

Access Complexity Graph

The exploitability of CVE-2026-77255 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-2026-77255

With low attack complexity and no required privileges, CVE-2026-77255 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-2026-77255, 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-2026-77255, 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-2026-77255 can result in unauthorized access to sensitive data, severely compromising data privacy.
  • Integrity: None
    CVE-2026-77255 poses no threat to data integrity.
  • Availability: None
    CVE-2026-77255 does not impact system availability.

CVE-2026-77255 References

External References

CWE Common Weakness Enumeration

CWE-441

CAPEC Common Attack Pattern Enumeration and Classification

  • XML Routing Detour Attacks CAPEC-219 An attacker subverts an intermediate system used to process XML content and forces the intermediate to modify and/or re-route the processing of the content. XML Routing Detour Attacks are Adversary in the Middle type attacks (CAPEC-94). The attacker compromises or inserts an intermediate system in the processing of the XML message. For example, WS-Routing can be used to specify a series of nodes or intermediaries through which content is passed. If any of the intermediate nodes in this route are compromised by an attacker they could be used for a routing detour attack. From the compromised system the attacker is able to route the XML process to other nodes of their choice and modify the responses so that the normal chain of processing is unaware of the interception. This system can forward the message to an outside entity and hide the forwarding and processing from the legitimate processing systems by altering the header information.
  • Transparent Proxy Abuse CAPEC-465 A transparent proxy serves as an intermediate between the client and the internet at large. It intercepts all requests originating from the client and forwards them to the correct location. The proxy also intercepts all responses to the client and forwards these to the client. All of this is done in a manner transparent to the client.

Vulnerable Configurations

  • cpe:2.3:a:mcp-atlassian:mcp_atlassian:0.1.4:*:*:*:*:*:*:*
    cpe:2.3:a:mcp-atlassian:mcp_atlassian:0.1.4:*:*:*:*:*:*:*
  • cpe:2.3:a:mcp-atlassian:mcp_atlassian:0.1.5:*:*:*:*:*:*:*
    cpe:2.3:a:mcp-atlassian:mcp_atlassian:0.1.5:*:*:*:*:*:*:*
  • cpe:2.3:a:mcp-atlassian:mcp_atlassian:0.1.6:*:*:*:*:*:*:*
    cpe:2.3:a:mcp-atlassian:mcp_atlassian:0.1.6:*:*:*:*:*:*:*
  • cpe:2.3:a:mcp-atlassian:mcp_atlassian:0.1.7:*:*:*:*:*:*:*
    cpe:2.3:a:mcp-atlassian:mcp_atlassian:0.1.7:*:*:*:*:*:*:*
  • cpe:2.3:a:mcp-atlassian:mcp_atlassian:0.1.8:*:*:*:*:*:*:*
    cpe:2.3:a:mcp-atlassian:mcp_atlassian:0.1.8:*:*:*:*:*:*:*
  • cpe:2.3:a:mcp-atlassian:mcp_atlassian:0.1.9:*:*:*:*:*:*:*
    cpe:2.3:a:mcp-atlassian:mcp_atlassian:0.1.9:*:*:*:*:*:*:*
  • cpe:2.3:a:mcp-atlassian:mcp_atlassian:0.1.10:*:*:*:*:*:*:*
    cpe:2.3:a:mcp-atlassian:mcp_atlassian:0.1.10:*:*:*:*:*:*:*
  • cpe:2.3:a:mcp-atlassian:mcp_atlassian:0.1.11:*:*:*:*:*:*:*
    cpe:2.3:a:mcp-atlassian:mcp_atlassian:0.1.11:*:*:*:*:*:*:*
  • cpe:2.3:a:mcp-atlassian:mcp_atlassian:0.1.12:*:*:*:*:*:*:*
    cpe:2.3:a:mcp-atlassian:mcp_atlassian:0.1.12:*:*:*:*:*:*:*
  • cpe:2.3:a:mcp-atlassian:mcp_atlassian:0.1.13:*:*:*:*:*:*:*
    cpe:2.3:a:mcp-atlassian:mcp_atlassian:0.1.13:*:*:*:*:*:*:*
  • cpe:2.3:a:mcp-atlassian:mcp_atlassian:0.1.14:*:*:*:*:*:*:*
    cpe:2.3:a:mcp-atlassian:mcp_atlassian:0.1.14:*:*:*:*:*:*:*
  • cpe:2.3:a:mcp-atlassian:mcp_atlassian:0.1.15:*:*:*:*:*:*:*
    cpe:2.3:a:mcp-atlassian:mcp_atlassian:0.1.15:*:*:*:*:*:*:*
  • cpe:2.3:a:mcp-atlassian:mcp_atlassian:0.1.16:*:*:*:*:*:*:*
    cpe:2.3:a:mcp-atlassian:mcp_atlassian:0.1.16:*:*:*:*:*:*:*
  • cpe:2.3:a:mcp-atlassian:mcp_atlassian:0.2.0:*:*:*:*:*:*:*
    cpe:2.3:a:mcp-atlassian:mcp_atlassian:0.2.0:*:*:*:*:*:*:*
  • cpe:2.3:a:mcp-atlassian:mcp_atlassian:0.2.1:*:*:*:*:*:*:*
    cpe:2.3:a:mcp-atlassian:mcp_atlassian:0.2.1:*:*:*:*:*:*:*
  • cpe:2.3:a:mcp-atlassian:mcp_atlassian:0.2.2:*:*:*:*:*:*:*
    cpe:2.3:a:mcp-atlassian:mcp_atlassian:0.2.2:*:*:*:*:*:*:*
  • cpe:2.3:a:mcp-atlassian:mcp_atlassian:0.2.3:*:*:*:*:*:*:*
    cpe:2.3:a:mcp-atlassian:mcp_atlassian:0.2.3:*:*:*:*:*:*:*
  • cpe:2.3:a:mcp-atlassian:mcp_atlassian:0.2.4:*:*:*:*:*:*:*
    cpe:2.3:a:mcp-atlassian:mcp_atlassian:0.2.4:*:*:*:*:*:*:*
  • cpe:2.3:a:mcp-atlassian:mcp_atlassian:0.2.5:*:*:*:*:*:*:*
    cpe:2.3:a:mcp-atlassian:mcp_atlassian:0.2.5:*:*:*:*:*:*:*
  • cpe:2.3:a:mcp-atlassian:mcp_atlassian:0.2.6:*:*:*:*:*:*:*
    cpe:2.3:a:mcp-atlassian:mcp_atlassian:0.2.6:*:*:*:*:*:*:*
  • cpe:2.3:a:mcp-atlassian:mcp_atlassian:0.3.0:*:*:*:*:*:*:*
    cpe:2.3:a:mcp-atlassian:mcp_atlassian:0.3.0:*:*:*:*:*:*:*
  • cpe:2.3:a:mcp-atlassian:mcp_atlassian:0.3.1:*:*:*:*:*:*:*
    cpe:2.3:a:mcp-atlassian:mcp_atlassian:0.3.1:*:*:*:*:*:*:*
  • cpe:2.3:a:mcp-atlassian:mcp_atlassian:0.4.0:*:*:*:*:*:*:*
    cpe:2.3:a:mcp-atlassian:mcp_atlassian:0.4.0:*:*:*:*:*:*:*
  • cpe:2.3:a:mcp-atlassian:mcp_atlassian:0.5.0:*:*:*:*:*:*:*
    cpe:2.3:a:mcp-atlassian:mcp_atlassian:0.5.0:*:*:*:*:*:*:*
  • cpe:2.3:a:mcp-atlassian:mcp_atlassian:0.6.0:*:*:*:*:*:*:*
    cpe:2.3:a:mcp-atlassian:mcp_atlassian:0.6.0:*:*:*:*:*:*:*
  • cpe:2.3:a:mcp-atlassian:mcp_atlassian:0.6.1:*:*:*:*:*:*:*
    cpe:2.3:a:mcp-atlassian:mcp_atlassian:0.6.1:*:*:*:*:*:*:*
  • cpe:2.3:a:mcp-atlassian:mcp_atlassian:0.6.2:*:*:*:*:*:*:*
    cpe:2.3:a:mcp-atlassian:mcp_atlassian:0.6.2:*:*:*:*:*:*:*
  • cpe:2.3:a:mcp-atlassian:mcp_atlassian:0.6.3:*:*:*:*:*:*:*
    cpe:2.3:a:mcp-atlassian:mcp_atlassian:0.6.3:*:*:*:*:*:*:*
  • cpe:2.3:a:mcp-atlassian:mcp_atlassian:0.6.4:*:*:*:*:*:*:*
    cpe:2.3:a:mcp-atlassian:mcp_atlassian:0.6.4:*:*:*:*:*:*:*
  • cpe:2.3:a:mcp-atlassian:mcp_atlassian:0.6.5:*:*:*:*:*:*:*
    cpe:2.3:a:mcp-atlassian:mcp_atlassian:0.6.5:*:*:*:*:*:*:*
  • cpe:2.3:a:mcp-atlassian:mcp_atlassian:0.7.0:*:*:*:*:*:*:*
    cpe:2.3:a:mcp-atlassian:mcp_atlassian:0.7.0:*:*:*:*:*:*:*
  • cpe:2.3:a:mcp-atlassian:mcp_atlassian:0.7.1:*:*:*:*:*:*:*
    cpe:2.3:a:mcp-atlassian:mcp_atlassian:0.7.1:*:*:*:*:*:*:*
  • cpe:2.3:a:mcp-atlassian:mcp_atlassian:0.8.0:*:*:*:*:*:*:*
    cpe:2.3:a:mcp-atlassian:mcp_atlassian:0.8.0:*:*:*:*:*:*:*
  • cpe:2.3:a:mcp-atlassian:mcp_atlassian:0.8.1:*:*:*:*:*:*:*
    cpe:2.3:a:mcp-atlassian:mcp_atlassian:0.8.1:*:*:*:*:*:*:*
  • cpe:2.3:a:mcp-atlassian:mcp_atlassian:0.8.2:*:*:*:*:*:*:*
    cpe:2.3:a:mcp-atlassian:mcp_atlassian:0.8.2:*:*:*:*:*:*:*
  • cpe:2.3:a:mcp-atlassian:mcp_atlassian:0.8.3:*:*:*:*:*:*:*
    cpe:2.3:a:mcp-atlassian:mcp_atlassian:0.8.3:*:*:*:*:*:*:*
  • cpe:2.3:a:mcp-atlassian:mcp_atlassian:0.8.4:*:*:*:*:*:*:*
    cpe:2.3:a:mcp-atlassian:mcp_atlassian:0.8.4:*:*:*:*:*:*:*
  • cpe:2.3:a:mcp-atlassian:mcp_atlassian:0.9.0:*:*:*:*:*:*:*
    cpe:2.3:a:mcp-atlassian:mcp_atlassian:0.9.0:*:*:*:*:*:*:*
  • cpe:2.3:a:mcp-atlassian:mcp_atlassian:0.10.0:*:*:*:*:*:*:*
    cpe:2.3:a:mcp-atlassian:mcp_atlassian:0.10.0:*:*:*:*:*:*:*
  • cpe:2.3:a:mcp-atlassian:mcp_atlassian:0.10.1:*:*:*:*:*:*:*
    cpe:2.3:a:mcp-atlassian:mcp_atlassian:0.10.1:*:*:*:*:*:*:*
  • cpe:2.3:a:mcp-atlassian:mcp_atlassian:0.10.2:*:*:*:*:*:*:*
    cpe:2.3:a:mcp-atlassian:mcp_atlassian:0.10.2:*:*:*:*:*:*:*
  • cpe:2.3:a:mcp-atlassian:mcp_atlassian:0.10.3:*:*:*:*:*:*:*
    cpe:2.3:a:mcp-atlassian:mcp_atlassian:0.10.3:*:*:*:*:*:*:*
  • cpe:2.3:a:mcp-atlassian:mcp_atlassian:0.10.4:*:*:*:*:*:*:*
    cpe:2.3:a:mcp-atlassian:mcp_atlassian:0.10.4:*:*:*:*:*:*:*
  • cpe:2.3:a:mcp-atlassian:mcp_atlassian:0.10.5:*:*:*:*:*:*:*
    cpe:2.3:a:mcp-atlassian:mcp_atlassian:0.10.5:*:*:*:*:*:*:*
  • cpe:2.3:a:mcp-atlassian:mcp_atlassian:0.10.6:*:*:*:*:*:*:*
    cpe:2.3:a:mcp-atlassian:mcp_atlassian:0.10.6:*:*:*:*:*:*:*
  • cpe:2.3:a:mcp-atlassian:mcp_atlassian:0.11.0:*:*:*:*:*:*:*
    cpe:2.3:a:mcp-atlassian:mcp_atlassian:0.11.0:*:*:*:*:*:*:*
  • cpe:2.3:a:mcp-atlassian:mcp_atlassian:0.11.1:*:*:*:*:*:*:*
    cpe:2.3:a:mcp-atlassian:mcp_atlassian:0.11.1:*:*:*:*:*:*:*
  • cpe:2.3:a:mcp-atlassian:mcp_atlassian:0.11.2:*:*:*:*:*:*:*
    cpe:2.3:a:mcp-atlassian:mcp_atlassian:0.11.2:*:*:*:*:*:*:*
  • cpe:2.3:a:mcp-atlassian:mcp_atlassian:0.11.3:*:*:*:*:*:*:*
    cpe:2.3:a:mcp-atlassian:mcp_atlassian:0.11.3:*:*:*:*:*:*:*
  • cpe:2.3:a:mcp-atlassian:mcp_atlassian:0.11.4:*:*:*:*:*:*:*
    cpe:2.3:a:mcp-atlassian:mcp_atlassian:0.11.4:*:*:*:*:*:*:*
  • cpe:2.3:a:mcp-atlassian:mcp_atlassian:0.11.5:*:*:*:*:*:*:*
    cpe:2.3:a:mcp-atlassian:mcp_atlassian:0.11.5:*:*:*:*:*:*:*
  • cpe:2.3:a:mcp-atlassian:mcp_atlassian:0.11.6:*:*:*:*:*:*:*
    cpe:2.3:a:mcp-atlassian:mcp_atlassian:0.11.6:*:*:*:*:*:*:*
  • cpe:2.3:a:mcp-atlassian:mcp_atlassian:0.11.7:*:*:*:*:*:*:*
    cpe:2.3:a:mcp-atlassian:mcp_atlassian:0.11.7:*:*:*:*:*:*:*
  • cpe:2.3:a:mcp-atlassian:mcp_atlassian:0.11.8:*:*:*:*:*:*:*
    cpe:2.3:a:mcp-atlassian:mcp_atlassian:0.11.8:*:*:*:*:*:*:*
  • cpe:2.3:a:mcp-atlassian:mcp_atlassian:0.11.9:*:*:*:*:*:*:*
    cpe:2.3:a:mcp-atlassian:mcp_atlassian:0.11.9:*:*:*:*:*:*:*
  • cpe:2.3:a:mcp-atlassian:mcp_atlassian:0.11.10:*:*:*:*:*:*:*
    cpe:2.3:a:mcp-atlassian:mcp_atlassian:0.11.10:*:*:*:*:*:*:*
  • cpe:2.3:a:mcp-atlassian:mcp_atlassian:0.11.11:*:*:*:*:*:*:*
    cpe:2.3:a:mcp-atlassian:mcp_atlassian:0.11.11:*:*:*:*:*:*:*
  • cpe:2.3:a:mcp-atlassian:mcp_atlassian:0.11.12:*:*:*:*:*:*:*
    cpe:2.3:a:mcp-atlassian:mcp_atlassian:0.11.12:*:*:*:*:*:*:*
  • cpe:2.3:a:mcp-atlassian:mcp_atlassian:0.12.0:*:*:*:*:*:*:*
    cpe:2.3:a:mcp-atlassian:mcp_atlassian:0.12.0:*:*:*:*:*:*:*
  • cpe:2.3:a:mcp-atlassian:mcp_atlassian:0.13.0:*:*:*:*:*:*:*
    cpe:2.3:a:mcp-atlassian:mcp_atlassian:0.13.0:*:*:*:*:*:*:*
  • cpe:2.3:a:mcp-atlassian:mcp_atlassian:0.13.1:*:*:*:*:*:*:*
    cpe:2.3:a:mcp-atlassian:mcp_atlassian:0.13.1:*:*:*:*:*:*:*
  • cpe:2.3:a:mcp-atlassian:mcp_atlassian:0.14.0:*:*:*:*:*:*:*
    cpe:2.3:a:mcp-atlassian:mcp_atlassian:0.14.0:*:*:*:*:*:*:*
  • cpe:2.3:a:mcp-atlassian:mcp_atlassian:0.14.1:*:*:*:*:*:*:*
    cpe:2.3:a:mcp-atlassian:mcp_atlassian:0.14.1:*:*:*:*:*:*:*
  • cpe:2.3:a:mcp-atlassian:mcp_atlassian:0.14.2:*:*:*:*:*:*:*
    cpe:2.3:a:mcp-atlassian:mcp_atlassian:0.14.2:*:*:*:*:*:*:*
  • cpe:2.3:a:mcp-atlassian:mcp_atlassian:0.14.3:*:*:*:*:*:*:*
    cpe:2.3:a:mcp-atlassian:mcp_atlassian:0.14.3:*:*:*:*:*:*:*
  • cpe:2.3:a:mcp-atlassian:mcp_atlassian:0.15.0:*:*:*:*:*:*:*
    cpe:2.3:a:mcp-atlassian:mcp_atlassian:0.15.0:*:*:*:*:*:*:*
  • cpe:2.3:a:mcp-atlassian:mcp_atlassian:0.16.0:*:*:*:*:*:*:*
    cpe:2.3:a:mcp-atlassian:mcp_atlassian:0.16.0:*:*:*:*:*:*:*
  • cpe:2.3:a:mcp-atlassian:mcp_atlassian:0.16.1:*:*:*:*:*:*:*
    cpe:2.3:a:mcp-atlassian:mcp_atlassian:0.16.1:*:*:*:*:*:*:*
  • cpe:2.3:a:mcp-atlassian:mcp_atlassian:0.17.0:*:*:*:*:*:*:*
    cpe:2.3:a:mcp-atlassian:mcp_atlassian:0.17.0:*:*:*:*:*:*:*
  • cpe:2.3:a:mcp-atlassian:mcp_atlassian:0.18.0:*:*:*:*:*:*:*
    cpe:2.3:a:mcp-atlassian:mcp_atlassian:0.18.0:*:*:*:*:*:*:*
  • cpe:2.3:a:mcp-atlassian:mcp_atlassian:0.18.1:*:*:*:*:*:*:*
    cpe:2.3:a:mcp-atlassian:mcp_atlassian:0.18.1:*:*:*:*:*:*:*
  • cpe:2.3:a:mcp-atlassian:mcp_atlassian:0.19.0:*:*:*:*:*:*:*
    cpe:2.3:a:mcp-atlassian:mcp_atlassian:0.19.0:*:*:*:*:*:*:*
  • cpe:2.3:a:mcp-atlassian:mcp_atlassian:0.20.0:*:*:*:*:*:*:*
    cpe:2.3:a:mcp-atlassian:mcp_atlassian:0.20.0:*:*:*:*:*:*:*
  • cpe:2.3:a:mcp-atlassian:mcp_atlassian:0.20.1:*:*:*:*:*:*:*
    cpe:2.3:a:mcp-atlassian:mcp_atlassian:0.20.1:*:*:*:*:*:*:*
  • cpe:2.3:a:mcp-atlassian:mcp_atlassian:0.21.0:*:*:*:*:*:*:*
    cpe:2.3:a:mcp-atlassian:mcp_atlassian:0.21.0:*:*:*:*:*:*:*

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