# CVE-2026-86043: Skipper: OPA body-authz bypass: truncated_body mitigation fails open on chunked/HTTP-2 (incomplete fix CVE-2026-50197)

> Attackers can bypass Open Policy Agent authorization in Skipper by sending chunked or HTTP/2 requests that exploit flawed body truncation logic.

- **Severity:** High 7.5 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 16 Sep 2026
- **Updated:** 16 Sep 2026
- **Also known as:** GHSA-5gpm-rgj3-9q76, GO-2026-6495

## What is CVE-2026-86043?

CVE-2026-86043 is a high-severity authentication bypass vulnerability in zalando skipper, published on 16 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

Skipper is an HTTP router and reverse proxy for service composition. Prior to version 0.27.37, the opaAuthorizeRequestWithBody filter can authorize an oversized request after Skipper truncates the body presented to Open Policy Agent because the input.truncated_body signal is derived from Content-Length rather than the actual read result. In filters/openpolicyagent/openpolicyagent.go, ExtractHttpBodyOptionally truncates bodies at maxBodyBytes, while filters/openpolicyagent/internal/envoy/skipperadapter.go copies the request headers without adding a Content-Length value that reflects the truncation. For an HTTP/1.1 request using Transfer-Encoding: chunked or an HTTP/2 request without Content-Length, a body-inspecting policy that follows the prior mitigation and permits input.truncated_body equal to false can evaluate only the truncated prefix, allow the request, and then forward the full oversized body to the protected upstream. This residual issue is distinct from CVE-2026-50197. This issue is fixed in version 0.27.37.

Weakness: CWE-863 (Incorrect Authorization)

## Which versions are affected by CVE-2026-86043?

3 open source packages ship an affected version, including github.com/zalando/skipper.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `github.com/zalando/skipper` | Go | All versions | 0.27.37 |
| `github.com/zalando/skipper` | Go | All versions | 0.27.37 |
| `github.com/zalando/skipper` | Go | All versions | 0.27.37 |

## How do I fix CVE-2026-86043?

Upgrade github.com/zalando/skipper to 0.27.37 or later.

## Is CVE-2026-86043 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-86043 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-86043 and fix it if it is affected.

What it is: CVE-2026-86043 is a high-severity authentication bypass vulnerability in zalando skipper, published on 16 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-86043 exists.

Affected packages and fixed versions:
- github.com/zalando/skipper (Go): affected all versions; fixed in 0.27.37
- github.com/zalando/skipper (Go): affected all versions; fixed in 0.27.37
- github.com/zalando/skipper (Go): affected all versions; fixed in 0.27.37

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-2026-86043/ (Markdown: https://insights.sbomify.com/CVE-2026-86043/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-86043
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-86043
- OSV: https://osv.dev/vulnerability/CVE-2026-86043

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-86043/
Summaries are generated and may contain mistakes; the official description above is the record.