Arbitrary File Write in Go "go tool pack" Extraction
CVE-2026-39817 is a path traversal / arbitrary file write vulnerability in the Go toolchain's "go tool pack" subcommand, a minimal archive utility similar to Unix ar and typically used internally by the compiler with trusted inputs. During archive extraction, the subcommand did not sanitize output filenames from archive members. As a result, a crafted malicious archive containing filenames with directory components could cause extracted files to be written outside the intended extraction location to attacker-chosen filesystem paths. Go fixed the issue by changing the pack subcommand to refuse extraction of files whose names contain directory components.
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Impact, mitigation & remediation
What it means. What to do now. Patch path, mitigations, and the assume-compromise checklist.
Impact
What an attacker gets, and what they’ve been doing with it.
Mitigation
If you can’t patch tonight, do this now.
Remediation
Patch, then assume compromise.
Exploits
No public exploits tracked yet. Mallory keeps watching.
No public exploit code observed for this vulnerability.
Affected products & vendors
Products and vendors Mallory has correlated with this vulnerability. Open in Mallory to drill down to specific CPE configurations and version ranges.
Vendor-confirmed product mapping. Mallory continuously reconciles this list against your asset inventory.
Recent activity
3 sources tracked across advisories, community write-ups, and news. New activity surfaces here as Mallory finds it.
The version that knows your environment.
Query your assets running an affected version, and investigate the blast radius.
Every observed campaign linking this CVE to a named adversary.
Malware families riding this exploit, with evidence and IOCs.
YARA, Sigma, Snort, and vendor rules, auto-deployed to your SIEM.
Cross-references every affected SKU, including bundled OEM variants.
Community discussion across Reddit, Mastodon, and other social sources.