CVE-2026-39817

Description

The "go tool pack" subcommand (usually used only by the compiler as an internal tool with known-good inputs) does not sanitize output filenames. Extracting a malicious archive file with the "pack" subcommand can write files to arbitrary locations on the filesystem.

CVSS v3.1 Score

5.9

MEDIUM

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

EPSS — Exploit Prediction

0.0001

Probability of exploitation

0.00%

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-787 Out-of-bounds Write

Affected Products

Vendor	Product	Versions
golang	go	< 1.25.10
golang	go	1.26.0 — 1.26.3

References

Advisories & Patches

https://go.dev/cl/767520 https://pkg.go.dev/vuln/GO-2026-4979

Other References

https://go.dev/issue/78778 https://groups.google.com/g/golang-announce/c/qcCIEXso47M

Frequently Asked Questions

What is CVE-2026-39817? +

The "go tool pack" subcommand (usually used only by the compiler as an internal tool with known-good inputs) does not sanitize output filenames. Extracting a malicious archive file with the "pack" subcommand can write files to arbitrary locations on the filesystem. It has a CVSS v3.1 base score of 5.9 (MEDIUM).

How severe is CVE-2026-39817? +

CVE-2026-39817 has a CVSS v3.1 score of 5.9 out of 10, rated MEDIUM. This is a medium-severity vulnerability that should be remediated as part of regular maintenance. The EPSS score is 0.0001, placing it in the 0th percentile for exploitation probability.

What products are affected by CVE-2026-39817? +

CVE-2026-39817 affects products from golang, specifically: go. Check the affected products table above for specific version ranges.

How do I check if I'm vulnerable to CVE-2026-39817? +

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.

Related Vulnerabilities

CVE-2026-3298

The method "sock_recvfrom_into()" of "asyncio.ProacterEventLoop" (Windows only) was missing a boundary check for the data buffer when using nbytes parameter. …

CVE-2026-40489

editorconfig-core-c is an EditorConfig core library for use by plugins supporting EditorConfig parsing. Versions up to and including 0.12.10 have …

CVE-2025-3154

Out-of-bounds array write in Xpdf 4.05 and earlier, triggered by an invalid VerticesPerRow value in a PDF shading dictionary.

CVE-2025-4640

Out-of-bounds Write vulnerability in PointCloudLibrary pcl allows Overflow Buffers. Since version 1.14.0, PCL by default uses a zlib installation from …

CVE-2025-5688

We have identified a buffer overflow issue allowing out-of-bounds write when processing LLMNR or mDNS queries with very long DNS …

CVE-2025-49848

An Out-of-bounds Write vulnerability exists within the parsing of PRJ files. The issues result from the lack of proper validation …