# CVE-2026-97039: Flag sanitization bypass via "#cgo pkg-config:" directives in cmd/go


- **Severity:** Not scored
- **Exploited in the wild:** Not known
- **Fix available:** Yes
- **Published:** 11 Nov 2026
- **Updated:** 11 Nov 2026
- **Also known as:** ALPINE-CVE-2026-97039, DEBIAN-CVE-2026-97039, GHSA-4x3g-87c5-vq62, GO-2026-6852, UBUNTU-CVE-2026-97039

## What is CVE-2026-97039?

CVE-2026-97039 is a vulnerability in cmd/go, published on 11 Nov 2026. 

### Official description

Building a malicious package that uses "#cgo pkg-config:" directives could load untrusted pkg-config ".pc" files or inject unvalidated compiler and linker flags. The pkg-config flag allowlist previously permitted "--with-path=" and "--personality=", allowed "--define-variable=" values beginning with "=" or "$" (which can rewrite paths in system ".pc" files into sysroot-prefixed "-L=" or "-L$SYSROOT" linker search paths), and allowed package arguments ending in ".pc" or containing path separators or "..", which caused pkg-config to load local ".pc" files directly from the package directory. In addition, flags returned by "pkg-config --cflags" in cgoCPPFLAGS were not checked when determining whether internal linking is safe. The go command now disallows "--with-path=", "--personality=", leading "=" or "$" characters in "--define-variable=" values, and local ".pc" paths in "#cgo pkg-config:" directives, and inspects cgoCPPFLAGS when checking internal linking compatibility.

## Which versions are affected by CVE-2026-97039?

1 open source package ship an affected version, including toolchain.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `toolchain` | Go | All versions | 1.26.11, 1.27.4 |

## How do I fix CVE-2026-97039?

Upgrade toolchain to a fixed version for your release line: 1.26.11 or 1.27.4.

## Is CVE-2026-97039 being exploited?

There is no known exploitation of CVE-2026-97039 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-97039 and fix it if it is affected.

What it is: CVE-2026-97039 is a vulnerability in cmd/go, published on 11 Nov 2026. 
Exploitation: There is no known exploitation of CVE-2026-97039 in the wild and no public exploit code.

Affected packages and fixed versions:
- toolchain (Go): affected all versions; fixed in 1.26.11, 1.27.4

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-97039/ (Markdown: https://insights.sbomify.com/CVE-2026-97039/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-97039
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-97039
- OSV: https://osv.dev/vulnerability/CVE-2026-97039

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-97039/
Summaries are generated and may contain mistakes; the official description above is the record.