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

Source: https://junglewise.ai/threats/cve-2026-56858-go-path-traversal-with-unescaped-forward-slash  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-08-13. Updated: 2026-09-25  
License: CC BY 4.0 with a link back

CVE-2026-56858 · Severity: medium · CVSS 6.1 · Published 2026-08-13

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.

Technologies: [stdlib (Go)](https://junglewise.ai/threats/technologies/go-stdlib). Vendors: [Go](https://junglewise.ai/threats/vendors/go).

## Quick answers

**Is CVE-2026-56858 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-56858 being exploited in the wild.

**How severe is CVE-2026-56858?** Medium severity, with a CVSS score of 6.1, published 13 August 2026.

**Which products and versions are affected?** stdlib (Go) SEMVER:introduced=0,fixed=1.25.13,introduced=1.26.0-0,fixed=1.26.6,introduced=1.27.0-0,fixed=1.27.0-rc.3.

**Is there a fix for CVE-2026-56858?** Yes. stdlib (Go): upgrade to 1.27.0-rc.3 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-56858 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-56858?** Check whether you run stdlib (Go) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## How to fix

- stdlib (Go): upgrade to 1.27.0-rc.3 or later

  ```sh
  go get stdlib@v1.27.0-rc.3
  ```


## 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

## Identifiers

- CVE-2026-56858
- GO-2026-6091

## Timeline

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

## References

- [https://pkg.go.dev/](https://pkg.go.dev/)
- [https://go.dev/cl/807100](https://go.dev/cl/807100)

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