Plunk: SNS webhook forgery

published 2026-05-08 6 mo ago modified 2026-10-26 13 d ago also EUVD-2026-28832

cvss: 9.1; version 3.1, CNA
cisa kev: Not listed; not in CISA's catalog
epss: 0.1%; EPSS 0.1% chance of exploitation in 30 days, percentile 2%
public exploits: 0; none known

Plunk is an open-source email platform built on top of AWS SES. Prior to version 0.9.0, the /webhooks/sns endpoint accepts Amazon SNS notification payloads from unauthenticated requests without verifying the SNS signature, certificate, or topic ARN, meaning anyone can forge a valid-looking webhook request. This allows an unauthenticated attacker to spoof SNS events to trigger workflow automations, unsubscribe contacts, manipulate email delivery metrics, and potentially exhaust billing credits. This issue has been patched in version 0.9.0.

Patch / fix

fixed in 1 links 1

useplunk plunk 0.9.0

github.com/useplunk/plunk/releases/tag/v0.9.0 release

CISA SSVC

Exploitation: none
Automatable: yes
Technical impact: total
Assessed: 5 mo ago (2026-05-11)

Exploit prediction

0.13% chance of exploitation in the next 30 days, higher than 2% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by	version	score	vector
CNA	3.1	9.1	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H

Affected products

useplunk plunk

Classification

Weakness

CWE-347 Improper Verification of Cryptographic Signature

References

Sources

CVE List CVE-2026-42193
NVD CVE-2026-42193

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

CPEs and fixed versions use Anchore's correction of NVD's data: Added CPE configurations because not yet analyzed by NVD.

Summary