CVE-2026-57511 (CVSS 5.4)

Description

SuperPlane before 0.30.0 contains an SMTP header injection vulnerability that allows unauthenticated attackers to inject arbitrary SMTP headers by including CRLF sequences in the event payload title field delivered via webhook. Attackers can manipulate the unsanitized title field passed to the SMTP DATA command to add Bcc recipients for content exfiltration, forge the From address to bypass SPF and DKIM checks, or inject Content-Type and MIME boundary headers to corrupt message bodies for phishing.

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CVSS v3.1 Score

5.4

MEDIUM

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:L/I:L/A:N

EPSS — Exploit Prediction

0.0024

Probability of exploitation

0.14%

Percentile rank

EPSS estimates the probability that this vulnerability will be exploited in the wild within the next 30 days. A higher score means more likely to be exploited.

Weakness Type (CWE)

CWE-93 CWE-93

References

Other References

https://github.com/superplanehq/superplane/commit/428c559dd2fa0aef3ba825a434a1b05c9abc7df7 https://github.com/superplanehq/superplane/pull/6354 https://github.com/superplanehq/superplane/releases/tag/v0.30.0 https://www.vulncheck.com/advisories/superplane-smtp-header-injection-via-webhook-event-title

Frequently Asked Questions

What is CVE-2026-57511? +

SuperPlane before 0.30.0 contains an SMTP header injection vulnerability that allows unauthenticated attackers to inject arbitrary SMTP headers by including CRLF sequences in the event payload title field delivered via webhook. Attackers can manipulate the unsanitized title field passed to the SMTP DATA command to add Bcc recipients for content exfiltration, forge the From address to bypass SPF and DKIM checks, or inject Content-Type and MIME boundary headers to corrupt message bodies for phishing. It has a CVSS v3.1 base score of 5.4 (MEDIUM).

How severe is CVE-2026-57511? +

CVE-2026-57511 has a CVSS v3.1 score of 5.4 out of 10, rated MEDIUM. This is a medium-severity vulnerability that should be remediated as part of regular maintenance. The EPSS score is 0.0024, placing it in the 0th percentile for exploitation probability.

How do I check if I'm vulnerable to CVE-2026-57511? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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