PatchSiren cyber security CVE debrief

CVE-2026-39904 gophish CVE debrief

CVE-2026-39904 is a high-severity denial of service vulnerability in Gophish, a popular open-source phishing toolkit. The vulnerability, which has a CVSS score of 7.1, allows authenticated users with the User role to upload a crafted Office document as an email template attachment, which can cause the server to run out of memory and terminate. This is possible because the ApplyTemplate() function in models/attachment.go processes Office documents as ZIP archives and calls ioutil.ReadAll() on each contained file entry without enforcing size restrictions on uncompressed content. As a result, a malicious user can upload a zip bomb payload that expands to several gigabytes in memory, causing the process to be terminated by the operating system. Users of Gophish should take immediate action to mitigate this vulnerability.

Vendor: gophish
Product: Unknown
CVSS: HIGH 7.1
CISA KEV: Not listed in stored evidence
Original CVE published: 2026-06-22
Original CVE updated: 2026-07-14
Advisory published: 2026-06-22
Advisory updated: 2026-07-14

Who should care

Users of Gophish, particularly those with authenticated users with the User role, should be aware of this vulnerability and take steps to mitigate it. This includes upgrading to a patched version of Gophish and monitoring for suspicious activity. Additionally, administrators should consider implementing compensating controls, such as limiting the size of email template attachments and monitoring server memory usage.

Technical summary

The vulnerability is caused by the ApplyTemplate() function in models/attachment.go, which processes Office documents as ZIP archives and calls ioutil.ReadAll() on each contained file entry without enforcing size restrictions on uncompressed content. This allows a malicious user to upload a zip bomb payload that can cause the server to run out of memory and terminate. The vulnerability has a CVSS score of 7.1 and is classified as a high-severity issue.

Defensive priority

High

Recommended defensive actions

Upgrade to a patched version of Gophish
Limit the size of email template attachments
Monitor server memory usage
Implement compensating controls, such as rate limiting and IP blocking
Monitor for suspicious activity

Evidence notes

The vulnerability was reported by Vulncheck and is described in a GitHub advisory. The CVE record was published on June 22, 2026, and the NVD detail was updated on June 23, 2026. The vulnerability has a CVSS score of 7.1 and is classified as a high-severity issue.

Sources and references

Verified primary and authoritative sources

CVE-2026-39904 CVE Program record
Publisher, destination, and source semantics verified

URL: https://www.cve.org/CVERecord?id=CVE-2026-39904

CVE Program - Official CVE Program record with source-provided CVE metadata.
CVE-2026-39904 NVD vulnerability detail
Publisher, destination, and source semantics verified

URL: https://nvd.nist.gov/vuln/detail/CVE-2026-39904

NIST National Vulnerability Database - Official NIST NVD detail page and source-specific vulnerability assessment.

Supplemental references

Source reference
Unverified legacy reference

URL: https://github.com/ashikmd7/GoPhish-0.12.1/blob/main/Unbounded%20Memory%20Allocation%20in%20Office%20Attachment%20Processing%20Leads%20to%20Server%20DoS/README.md

[email protected]
Source reference
Unverified legacy reference

URL: https://www.vulncheck.com/advisories/gophish-denial-of-service-via-office-document-upload

[email protected]

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.