CVE-2026-97040 Cgo directive injection via .syso files disguised as Go object files in cmd/go and cmd/link
- Exploited in the wild
- Not known
- Fix
- Available
What is CVE-2026-97040?
CVE-2026-97040 is a vulnerability in cmd/go, published on 11 Nov 2026.
Official description
Building a package containing a crafted ".syso" file could bypass cgo flag validation and inject arbitrary linker flags when linking. When loading ".syso" entries from a package archive, the linker only checked for recognized host object headers (ELF, Mach-O, PE, and XCOFF) before falling through to Go object parsing. A ".syso" file beginning with a "go object" header was parsed as a Go compiler object, allowing untrusted cgo metadata directives (such as "cgo_ldflag" or "cgo_dynamic_linker") embedded in the ".syso" file to be passed to the external linker without validation. Additionally, ".syso" filenames longer than 16 bytes lost their ".syso" extension when truncated in archive headers, and unrecognized ".syso" formats forced external linking in pure-Go builds. The linker now rejects ".syso" files that are not recognized host object formats, and "cmd/go" and "cmd/pack" preserve the ".syso" suffix when truncating long archive member names.
Which versions are affected by CVE-2026-97040?
1 open source package ship an affected version, including toolchain.
| Package | Affected | Fixed in |
|---|---|---|
toolchain Go | All versions | 1.26.11, 1.27.4 |
How do I fix CVE-2026-97040?
Upgrade toolchain to a fixed version for your release line: 1.26.11 or 1.27.4.
Is CVE-2026-97040 being exploited?
There is no known exploitation of CVE-2026-97040 in the wild and no public exploit code.
Sources
Also known as ALPINE-CVE-2026-97040, DEBIAN-CVE-2026-97040, GHSA-9767-p5x8-v2p2, GO-2026-6851, UBUNTU-CVE-2026-97040.