# CVE-2026-97039: Go command unsafe pkg-config flag handling in cgo

Source: https://junglewise.ai/threats/cve-2026-97039-building-a-malicious-package-that-uses-cgo-pkg-config-directives  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-11-11. Updated: 2026-11-11  
License: CC BY 4.0 with a link back

CVE-2026-97039 · Severity: info · Published 2026-11-11

The Go compiler's cgo build tool could be tricked into loading untrusted configuration files and injecting malicious compiler flags when processing malicious packages. An attacker could craft a malicious Go package that, when compiled, loads local or system pkg-config files from unexpected locations or injects unvalidated compiler and linker flags, potentially leading to arbitrary code injection during the build process.

Technologies: [go (Go)](https://junglewise.ai/threats/technologies/go), [toolchain (Go)](https://junglewise.ai/threats/technologies/toolchain). Vendors: [Go](https://junglewise.ai/threats/vendors/go).

## Quick answers

**Is CVE-2026-97039 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-97039 being exploited in the wild.

**How severe is CVE-2026-97039?** Informational severity, published 11 November 2026.

**Which products and versions are affected?** go (Go) before the fix; toolchain (Go) SEMVER:introduced=0,fixed=1.26.11,introduced=1.27.0-0,fixed=1.27.4.

**Is there a fix for CVE-2026-97039?** Yes. toolchain (Go): upgrade to 1.27.4 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-97039 attacked?** It is attacked with local access, in a software library.

**Am I affected by CVE-2026-97039?** Check whether you run go (Go) or toolchain (Go) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## How to fix

- toolchain (Go): upgrade to 1.27.4 or later

  ```sh
  go get toolchain@v1.27.4
  ```


## Technical details

The Go command's cgo subsystem failed to properly validate pkg-config directives and flags in "#cgo pkg-config:" pragmas. The vulnerability allows local ".pc" file loading from package directories, unsanitized "--define-variable=" values that can rewrite system paths, and dangerous flags like "--with-path=" and "--personality=". Additionally, cgoCPPFLAGS output was not inspected when determining internal linking safety. Exploitation requires building a malicious package locally or accepting one from an untrusted source.

## Affected products

- Go Go before the fix

## Identifiers

- CVE-2026-97039
- GO-2026-6852

## Timeline

- 2026-11-11: disclosed

## References

- [https://pkg.go.dev/](https://pkg.go.dev/)
- [https://go.dev/cl/862152](https://go.dev/cl/862152)

## Related threats

- [Go cgo LDFLAGS validation bypass in cmd/cgo](https://junglewise.ai/threats/cve-2026-97043-building-a-malicious-package-that-uses-cgo-could-bypass-cgo)
- [Go compiler unsafe library path validation in Windows linker](https://junglewise.ai/threats/cve-2026-97042-building-a-malicious-package-that-uses-go-cgo-import-dynamic-or)
- [Go compiler cgo linker flag injection via directives](https://junglewise.ai/threats/cve-2026-97041-building-a-malicious-package-containing-go-cgo-compiler)
- [Go linker arbitrary flag injection via crafted .syso files](https://junglewise.ai/threats/cve-2026-97040-building-a-package-containing-a-crafted-syso-file-could-bypass)
- [Go linker code injection via malicious package compilation](https://junglewise.ai/threats/cve-2026-97038-building-a-malicious-package-containing-syso-files-or-cgo-linker)