CVE-2026-56858: Go path traversal with unescaped forward slash

Executive brief

A vulnerability in Go's path handling allows attackers to inject arbitrary content through malformed input that closes path segments prematurely with an unescaped forward slash, potentially leading to cross-site scripting (XSS) attacks. This affects applications using Go's path processing functions with untrusted input.

Technical details

The vulnerability is a path traversal/injection flaw in Go's path handling logic where pathological inputs containing unescaped forward slashes can prematurely close path segments, allowing attacker-controlled data to inject arbitrary content. The root cause involves insufficient escaping or validation of forward slash characters in path processing. The attack is network-reachable and does not require authentication, though it depends on the affected application processing user-supplied paths. An attacker can achieve XSS or other injection attacks by crafting malicious path inputs. A patch has been committed (referenced in CL 807100).

Affected products

• Go Go

Timeline

• 2026-08-13: disclosed
• other: CVE-2026-56858 assigned

References

• https://pkg.go.dev/
• https://go.dev/cl/807100