Skip to content
Fencer Intel
no cvss —

CVE-2026-97040 json

Cgo directive injection via .syso files disguised as Go object files in cmd/go and cmd/link

published yesterday modified yesterday also EUVD-2026-123105 , GO-2026-6851

cvss
—
not scored
cisa kev
Not listed
not in CISA's catalog
epss
0.2%
EPSS 0.2% chance of exploitation in 30 days, percentile 15%
public exploits
0
none known

Summary

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.

Patch / fix

  • go toolchain 1.26.11, 1.27.4
  • Go toolchain cmd/go 1.26.11, 1.27.4
  • Go toolchain cmd/link 1.26.11, 1.27.4

Is CVE-2026-97040 in your dependencies? Fencer shows which of your repositories are affected as soon as an advisory lands, and opens the fix as a pull request.

Check with Fencer

Exploit prediction

0.25% chance of exploitation in the next 30 days, higher than 15% of all scored CVEs (FIRST EPSS, 2026-11-11).

Affected packages

ecosystem package affected fixed in
go toolchain
<1.26.11
>=1.27.0-0, <1.27.4
1.26.11
1.27.4

Affected products

  • Go toolchain cmd/go
  • Go toolchain cmd/link

Classification

Weakness
  • CWE-94 Improper Control of Generation of Code

References

Sources

Fencer Intel keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.