CVE-2026-77136
CVE-2026-77136 is a critical-severity vulnerability with a CVSS 4.0 base score of 9.5. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-1336.
Key facts
- Severity: Critical (CVSS 4.0 base score 9.5)
- EPSS exploit prediction: 1% (61st percentile)
- Actively exploited: Not listed in CISA KEV
- Weakness: CWE-1336
- Published:
- Last modified:
Description
The extension passes the raw value of a form field configured as "This field contains the name of the sender" directly into a Fluid View as template source, without any sanitization, and renders it. An anonymous, unauthenticated user can submit Fluid template syntax in that field to execute arbitrary Fluid ViewHelpers leading to disclosure of server configuration, environment variables and application source, and potentially remote code execution. Exploitation requires only that a form field is configured as the sender_name field, a common and default-adjacent Powermail configuration. No authentication or user interaction beyond a normal form submission is required. This vulnerability is reported to be actively exploited in the wild.
Frequently asked questions
- What is CVE-2026-77136?
- The extension passes the raw value of a form field configured as "This field contains the name of the sender" directly into a Fluid View as template source, without any sanitization, and renders it. An anonymous, unauthenticated user can submit Fluid template syntax in that field to execute arbitrary Fluid ViewHelpers leading to disclosure of server configuration, environment variables and application source, and potentially remote code execution. Exploitation requires only that a form field is configured as the sender_name field, a common and default-adjacent Powermail configuration. No authentication or user interaction beyond a normal form submission is required. This vulnerability is reported to be actively exploited in the wild.
- How severe is CVE-2026-77136?
- CVE-2026-77136 has a CVSS 4.0 base score of 9.5, rated critical severity.
- Is CVE-2026-77136 being actively exploited?
- It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (61st percentile), an estimate of the probability of exploitation in the next 30 days.
- How do I fix CVE-2026-77136?
- Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.
- When was CVE-2026-77136 published?
- CVE-2026-77136 was published on 2026-08-25 and last updated on 2026-09-28.
References
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