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CVE-2026-97039GO-2026-6852

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

Exploited
No known exploitation
Fix
Fixed in 1.26.11, 1.27.4
Who is exposed
Not reported

Do first: Upgrade to a fixed version: 1.26.11, 1.27.4.

Published
Last modified
Reference
Last checked
10/100 · provisional
None on Exploit-DB, Metasploit or GitHub

Summary

The Go command (cmd/go) can be tricked, when building a malicious package that uses "#cgo pkg-config:" directives, into loading untrusted pkg-config ".pc" files or injecting unvalidated compiler and linker flags. The flaw stems from weak flag filtering and local ".pc" file handling, which an attacker could use to redirect linker search paths or load local files from the package directory.

Written by anthropic/claude-haiku-5.5 from the sources below. Verify against them.

Read the original 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.

cve.now Index

10Pcve.now Index 10 of 100 · methodology v3 · provisional
  • Exploitation?/40Unknown. No CISA SSVC exploitation rating yet
  • Exposure?/25Unknown. No advisory context yet
  • Reach10/20Affects Go packages
  • Severity?/10Unknown. No CVSS score or vendor rating
  • No patch0/5No signal

What would change the score

  • Would score about 65 if added to CISA KEV
  • Would score about 60 if CISA's SSVC rates exploitation active
  • Would score about 32 if advisories confirm default setups are exposed

How the score works · Rankings

What to do

  • Upgrade to a fixed version: 1.26.11, 1.27.4.

Check your systems with an agent

Paste this into a coding or ops agent. It checks your systems read-only and reports a table per asset.

Check whether my systems are affected by CVE-2026-97039 (Flag sanitization bypass via "#cgo pkg-config:" directives in cmd/go), using the cve.now data below.

Rules: work read-only. Do not run exploit code, proof-of-concept scripts or scanners that send attack payloads, and do not change any configuration, package, image or deployment. Report findings only.

What cve.now has for CVE-2026-97039 (entry last updated 2026-11-11):
Affected:
- Go package cmd/go: fixed in 1.26.11; from 1.27.0-0, fixed in 1.27.4
- Go package toolchain: fixed in 1.26.11; from 1.27.0-0, fixed in 1.27.4
Fixed versions: 1.26.11, 1.27.4.
Setup: unknown whether the bug needs a non-default feature or setting. Check the advisory.
CISA KEV: CVE-2026-97039 is not listed as of cve.now's last read.
This KEV status is for CVE-2026-97039 only. If you also check another CVE, look up its own KEV status; never assume it from this one.

How to check:
- Packages (Go): find every lockfile in each project and run check_stack from the cve.now MCP server on each one. Compare the resolved versions, not the ranges a manifest declares, with the affected versions above. Include transitive dependencies.

Verify against the linked advisories before concluding, and cite the date you read each one:
- https://go.dev/cl/862152
- https://go.dev/issue/82571
- https://groups.google.com/g/golang-announce/c/iY8TY0wWgbM
- https://pkg.go.dev/vuln/GO-2026-6852
Do not conclude an asset is unaffected unless you checked it and the evidence covers both its version and the conditions above. If you could not check something, mark it unknown and say what is missing.

Report a table with one row per asset and these columns: Asset | Version or build | Status (affected, fixed, not applicable, unknown) | Compensating controls | Exposure (internet-facing, internal, none) | Evidence | Next action.

Entry: https://cve.now/CVE-2026-97039
For follow-up questions, use the cve.now MCP server at https://mcp.cve.now/mcp (no authentication), for example get_vulnerability with id CVE-2026-97039.

Timeline

  1. CVE published
  2. First seen by cve.now

Affected versions

  • fixed in 1.26.11; From 1.27.0-0 · fixed in 1.27.4

  • fixed in 1.26.11; From 1.27.0-0 · fixed in 1.27.4

Evidence 6

CVE record · 2

Establishes: The identifier and description.

  1. Record
  2. Record

Other links · 4

  1. Link
  2. Link
  3. Link
  4. Link

Corrections

None so far.

Something wrong on this page? Report an error. Every fix is listed here.

Questions about CVE-2026-97039

Is CVE-2026-97039 being exploited?

It is not in CISA's Known Exploited Vulnerabilities catalog, and CISA's SSVC assessment does not mark exploitation as active. That does not mean it has not been attacked: vendors and researchers can report attacks before CISA lists them. No public exploit code is tracked.Source: cve.now feed data

Which versions are affected by CVE-2026-97039?

cmd/go (Go): before 1.26.11; from 1.27.0-0 before 1.27.4. toolchain (Go): before 1.26.11; from 1.27.0-0 before 1.27.4.Source: cve.now feed data

How do I fix CVE-2026-97039?

Upgrade to a fixed version: 1.26.11, 1.27.4.Source: cve.now feed data

Sources

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