VulnSocial

CVE-2026-55549Disclosure

LOWCVSS 6.5 · MEDIUM

Exploit discussion active in current signal (1 latest mentions)

Immediate actions

  • Prioritize remediation for affected systems immediately
  • Hunt for exploitation attempts and persistence artifacts
  • Increase monitoring for publicly documented tradecraft
  • Track advisory updates for patch or workaround availability

Recommended action window: High priority (within 72h)

NVD 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.

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3.5/ 10 priority

Sources & remediation

Other references
Weakness type (CWE)
CWE-79

Priority

LOW

Exploitation

NONE

PoC

YES

Patch

NONE

Momentum

NONE

Threat summary

  • Public PoC and exploit tooling are both present
  • 1 mentions across 1 observed day

What's happening

  • Exploit tool or code specified in 1 signal
  • PoC mentioned or linked in 1 signal
  • Technical details provided in 1 signal
  • Disclosure: 1 classified signal
  • 1 total mentions across 1 day

Deep dive

Activity timeline1 mentions / 1d
00111Mentions · 2026-09-18: 1PoC Mentioned / Linked · 2026-09-18: 1Exploit Tool / Code · 2026-09-18: 1Technical Details · 2026-09-18: 109-18
Signal classification1 categories
Disclosure
1100.0%
Referenced assets1 URL
By indicator
Full discourse1 post
  • pdnuclei-bot@pdnuclei_bot
    Disclosure

    🚨 CVE-2026-55549 - medium 🚨 Yamcs <=5.8.6 - Cross-Site Scripting > Yamcs < 5.9.4 contains a stored XSS caused by inadequate HTML escaping of attacker-co... 👾 https://cloud.projectdiscovery.io/library/CVE-2026-55549 @pdnuclei #NucleiTemplates #cve

    Post summary

    The tweet primarily announces CVE-2026-55549, a stored XSS vulnerability in Yamcs versions prior to 5.9.4, providing technical details and referencing Nuclei templates via a ProjectDiscovery library link, but the core message is vulnerability disclosure rather than exploit availability or active exploitation.

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