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CVE-2026-55549— Yamcs: Reflected XSS in the URL of the Authorize Endpoint

Quick assessment

Affected
yamcs yamcs
Exploitation
Public or AI PoC available; prioritize validation
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Yamcs是Yamcs团队的一款航天任务遥测数据管理软件。 Yamcs 5.9.4之前版本存在跨站脚本漏洞，该漏洞源于对来自GET /auth/authorize的redirect_uri参数未进行充分的HTML转义，可能导致跨站脚本攻击，攻击者通过特制授权URL在用户打开时执行JavaScript，访问浏览器持有的认证材料并传输给攻击者，从而导致账户接管。

CVSS 6.5 · Medium EPSS 1.31% · P70

Public Exploits 1

Nuclei · 1 CVE-2026-55549.yaml [template]

Possible ATT&CK Techniques 1 AI

T1189 · Drive-by Compromise

Affected Version Matrix 1

VendorProduct Version RangeStatus
yamcs yamcs < 5.9.4 affected
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I. Basic Information for CVE-2026-55549

Vulnerability Information
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Vulnerability Title
Yamcs: Reflected XSS in the URL of the Authorize Endpoint
Source: CVE Program / CVE List V5
Vulnerability Description
Yamcs is a mission control framework. Prior to 5.9.4, Yamcs reflects an attacker-controlled redirect_uri parameter from GET /auth/authorize into yamcs-core/src/main/resources/auth/templates/authorize.html without adequate HTML escaping by yamcs-core/src/main/java/org/yamcs/http/auth/AuthHandler.java and yamcs-core/src/main/java/org/yamcs/http/HandlerContext.java. A crafted authorization URL can execute JavaScript when opened by a Yamcs user. The script can access browser-held authentication material and transmit it to an attacker, enabling account compromise. This issue is fixed in version 5.9.4.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:N
Source: CVE Program / CVE List V5
Vulnerability Type
在Web页面生成时对输入的转义处理不恰当(跨站脚本)
Source: CVE Program / CVE List V5
Vulnerability Title
Yamcs 跨站脚本漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Yamcs是Yamcs团队的一款航天任务遥测数据管理软件。 Yamcs 5.9.4之前版本存在跨站脚本漏洞，该漏洞源于对来自GET /auth/authorize的redirect_uri参数未进行充分的HTML转义，可能导致跨站脚本攻击，攻击者通过特制授权URL在用户打开时执行JavaScript，访问浏览器持有的认证材料并传输给攻击者，从而导致账户接管。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
yamcs yamcs < 5.9.4 -

II. Public POCs for CVE-2026-55549

# POC Description Source Link Shenlong Link
1 Yamcs < 5.9.4 contains a stored XSS caused by inadequate HTML escaping of attacker-controlled redirect_uri parameter in authorization template, letting attackers execute JavaScript to steal authentication data, exploit requires user to open crafted URL. https://github.com/projectdiscovery/nuclei-templates/blob/main/http/cves/2026/CVE-2026-55549.yaml POC Details
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III. Intelligence Information for CVE-2026-55549

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Patches & Fixes for CVE-2026-55549 (1)

Vendor Advisories for CVE-2026-55549 (1)

Same Patch Batch · yamcs · 2026-08-28 · 9 CVEs total

CVE-2026-55565 9.9 CRITICAL Yamcs: Authenticated remote code execution via unescaped StreamSQL `LIKE` pattern compiled
CVE-2026-55559 9.8 CRITICAL Yamcs: Remote Code Execution via instance-template argument YAML injection (createInstance
CVE-2026-55511 9.1 CRITICAL Yamcs: Authenticated RCE via StreamSQL aggregate-compiler column-name injection in Yamcs `
CVE-2026-55521 8.8 HIGH Yamcs : Multiple Missing Function Level Access Control vulnerabilities in Yamcs Core API
CVE-2026-55552 7.5 HIGH Yamcs: Unauthenticated Directory Traversal
CVE-2026-55545 6.5 MEDIUM Yamcs: WebSocket subscription handlers omit the privilege checks their REST siblings enfor
CVE-2026-55547 4.3 MEDIUM Yamcs: Missing Authorization on Role and Privilege Enumeration Endpoints Allows Any Authen
CVE-2026-55566 4.3 MEDIUM Yamcs: DOM XSS in Extension Routing

IV. Related Vulnerabilities

Same product: yamcs
Same vendor: yamcs
Same weakness: CWE-79

V. Comments for CVE-2026-55549

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