CVE-2026-55559Public exploitNetwork attack vectorHinoki check available

Remote code execution via template argument YAML injection

Published Aug 28, 2026 · Updated Aug 28, 2026

Code injection in Space Applications Services Yamcs before 5.12.8 and 5.13.0 through 5.13.1 allows remote attackers to execute commands. VarStatement.append inserts templateArgs into rendered YAML without context escaping, so the parser accepts an injected services entry for org.yamcs.ProcessRunner. The API is unauthenticated without security.yaml; otherwise CreateInstances privilege is required, and commands run as the Yamcs service account.

CVSS severity9.8
Critical
EPSS probability0.55%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkAvailable
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Summary

What happened

Code injection in Space Applications Services Yamcs before 5.12.8 and 5.13.0 through 5.13.1 allows remote attackers to execute commands. VarStatement.append inserts templateArgs into rendered YAML without context escaping, so the parser accepts an injected services entry for org.yamcs.ProcessRunner. The API is unauthenticated without security.yaml; otherwise CreateInstances privilege is required, and commands run as the Yamcs service account.

The record

CVE
CVE-2026-55559
Published
Aug 28, 2026
Updated
Aug 28, 2026
Vendor
Space Applications Services
Product
Yamcs
Classifications
CWE-1336, CWE-94, CWE-470, T1190
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Aug 28, 2026CVE publishedPublication date reported by the CVE source.
  2. Aug 28, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=< 5.12.8
  2. Affected versionversion=>= 5.13.0, < 5.13.2

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Space Applications Services · Yamcsversion=< 5.12.8; version=>= 5.13.0, < 5.13.2

Published CVSS scores

9.8GitHub CNACVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-1336Improper Neutralization of Special Elements Used in a Template Engine
CWE-94Improper Control of Generation of Code ('Code Injection')
CWE-470Use of Externally-Controlled Input to Select Classes or Code ('Unsafe Reflection')
T1190Exploit Public-Facing Application

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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