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VulnerabilityPublished Updated

CVE-2026-42193: useplunk plunk · Improper Verification of Cryptographic Signature

Affects useplunk plunkSource CVE Database V5

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Not known to be exploited · CVSS 9.1 Critical : upgrade to 0.9.0 as a priority.

Data as of 9 Nov 2026, 23:24 UTC

CVSS 3.1 base score
9.1Critical
How severe the flaw is on the 0–10 CVSS scale.

Contested

Critical score, yet low EPSS after six months
EPSS
0.1% chance of exploitation in 30 days – higher than 2% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch
Available – fixed in 0.9.0
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 8 May 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponized: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 10 Nov 2026.

What to do

Upgrade plunk and useplunk/plunk to 0.9.0.

Affected software

ProductAffectedFixed in
useplunkplunkAffected
  • <0.9.0
Fixed in
  • 0.9.0
GitHubuseplunk/plunkpkg:github/useplunk/plunkOther threatsAffected
  • <0.9.0
Fixed in
  • 0.9.0

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

A patch addressing this vulnerability is available in plunk version 0.9.0. Users should upgrade to version 0.9.0 or later to ensure proper verification of SNS webhook requests. Since plunk is a cloud-hosted service, the vendor manages remediation for this service; users should verify with the vendor that their instance is updated. Patch status is confirmed as available. No additional mitigation steps are specified by the vendor.

Description

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.

References

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