# CVE-2026-56329: Capgo - Cross-Tenant Preview Namespace Collision via Non-Bijective Underscore Decoding

> Attackers can cause cross-tenant preview misrouting and denial of service by exploiting non-bijective underscore decoding in Capgo's hostname parsing.

- **Severity:** Medium 5.3 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:L/VA:L/SC:N/SI:L/SA:L`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 10 Jul 2026
- **Updated:** 10 Jul 2026
- **Also known as:** GHSA-42q8-ww2w-fgmm, GHSA-76qq-gg2p-pwwj

## What is CVE-2026-56329?

CVE-2026-56329 is a medium-severity vulnerability in Capgo, published on 10 Jul 2026. Any signed-in user can exploit it over the network, with no action from the victim.

### Official description

Capgo before 12.128.2 contains a cross-tenant preview namespace collision vulnerability caused by non-bijective decoding of double underscores to dots in preview hostname parsing. Attackers can register app IDs with underscores that collide with other tenants' dotted app IDs, causing preview misrouting and denial of preview access for victim applications.

Weakness: CWE-436 (Interpretation Conflict)

## Which versions are affected by CVE-2026-56329?


## How do I fix CVE-2026-56329?

No fix has been published for CVE-2026-56329 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-56329 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-56329 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-56329 and fix it if it is affected.

What it is: CVE-2026-56329 is a medium-severity vulnerability in Capgo, published on 10 Jul 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-56329 exists.

Affected product: Capgo. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-56329/ (Markdown: https://insights.sbomify.com/CVE-2026-56329/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-56329
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-56329
- OSV: https://osv.dev/vulnerability/CVE-2026-56329

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-56329/
Summaries are generated and may contain mistakes; the official description above is the record.