CVE-2026-39817 Invoking "go tool pack" does not sanitize output paths in cmd/go
Attackers can write files to arbitrary locations via malicious archives processed by the Go pack tool, potentially leading to code execution or data modification.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Local or same network only
- Victim action needed
- A user has to click or open something
- Fix
- Available
What is CVE-2026-39817?
CVE-2026-39817 is a medium-severity path traversal vulnerability in Golang Go, published on 7 May 2026. It can only be exploited from the same machine or local network, and only if a user opens a file or follows a link.
Official 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.
Weakness: CWE-787
Which versions are affected by CVE-2026-39817?
2 open source packages ship an affected version, including golang and toolchain. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
golang Bitnami | All versions | 1.25.10, 1.26.3 |
toolchain Go | All versions | 1.25.10, 1.26.3 |
Products include Golang Go.
How do I fix CVE-2026-39817?
Upgrade golang to a fixed version for your release line: 1.25.10 or 1.26.3.
Upgrade, and resolve every user-supplied path against an allowed base folder before opening it. More about Path traversal.
Is CVE-2026-39817 being exploited?
There is no known exploitation of CVE-2026-39817 in the wild and no public exploit code.
Other vulnerabilities in Golang Go
- CVE-2020-0601 Microsoft Windows CryptoAPI Spoofing
- CVE-2026-27143 Missing bound checks can lead to memory corruption in safe Go in cmd/compile
- CVE-2024-24790 Unexpected behavior from Is methods for IPv4-mapped IPv6 addresses in net/netip
- CVE-2023-39320 Arbitrary code execution via go.mod toolchain directive in cmd/go
- CVE-2023-24540 Improper handling of JavaScript whitespace in html/template
Sources
Also known as AZL-98892, BELL-CVE-2026-39817, BIT-golang-2026-39817, CLEANSTART-2026-IG50576, CLEANSTART-2026-LU46498, CLEANSTART-2026-RQ22332 and 790 more.