CVE-2026-55521
Authz bypass in Yamcs lets low-privilege users read indices, control COP-1 links, and change time.
Is CVE-2026-55521 being exploited?
Not confirmed. CVE-2026-55521 does not appear in CISA's Known Exploited Vulnerabilities catalog, which records only exploitation that has been observed and reported publicly. That is evidence of absence of a report, not evidence the flaw is unattacked. EPSS currently estimates a 0.36% probability of exploitation in the next 30 days.
How severe is CVE-2026-55521?
CVE-2026-55521 is rated High with a CVSS score of 8.8. Severity describes how bad exploitation would be, not how likely it is: pair it with exploitation evidence before deciding what to patch first.
Is there a patch for CVE-2026-55521?
Yes. A fix has been recorded for CVE-2026-55521. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2026-55521 affect?
CVE-2026-55521 affects Yamcs versions prior to 5.12.8 and 5.13.2. Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
What should I do about CVE-2026-55521?
Upgrade to Yamcs 5.12.8 or 5.13.2; restrict access, rotate credentials, and audit logs.
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
Authenticated low-privilege users can read packet/event metadata, alter COP-1 link state (disrupt telecommands), and set system/simulation time, affecting integrity and availability.
Immediate action required
- affected< 5.12.8
- affected>= 5.13.0 and < 5.13.2
As published in the CVE Program record. A version outside these ranges is not a statement that it is unaffected — vendors sometimes understate a range, and distribution-backported builds carry upstream numbers that do not reflect what was patched into them.