Skipper: Incomplete fix for CVE-2026-50197: an oversized body can bypass OPA deny-on-presence Rego policies

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

8.2 · CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:L/A:N

EPSS

• CVE-2026-65838: 0.46% estimated exploitation activity in the next 30 days; percentile 40.24 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Summary A wrong policy can be an open door. You have to check input.attributes.request.http.truncatedbody in your policy. Description Incomplete fix for CVE-2026-50197: an oversized declared-Content-Length body still hands OPA an empty parsedbody, so deny-on-presence Rego policies fail OPEN while the full payload reaches upstream. The CVE-2026-50197 fix (commit 3152f3b0, PR #4041, v0.26.10) substituted expectedSize = maxBodyBytes only when req.ContentLength < 0 (chunked / HTTP/2 without content-length). But when a request declares a Content-Length larger than maxBodyBytes, expectedSize maxBodyBytes, the body-extraction if is skipped entirely, and ExtractHttpBodyOptionally returns rawBodyBytes = nil — so OPA evaluates an empty parsedbody, while the full forbidden payload still flows to the upstream. A deny-on-presence policy (default allow = true; allow = false if input.parsedbody.<forbidden) — the exact Rego shape the advisory describes — fails OPEN. The fix's own comment reasons…

Published by the source

17 Jul 2026, 21:49 UTC

Last modified by the source

25 Sep 2026, 17:03 UTC

Source last checked

26 Oct 2026, 15:29 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-8qqm-fp2q-v734

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# Patch Next advisory brief: CVE-2026-65838

Advisory: Skipper: Incomplete fix for CVE-2026-50197: an oversized body can bypass OPA deny-on-presence Rego policies
IDs: CVE-2026-65838, GHSA-8qqm-fp2q-v734
Record: https://patchnext.com/advisories/cve-2026-65838 (revision 1, source checked 26 Oct 2026, 15:29 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 8.2)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: github.com/zalando/skipper 0.27.26. A vendor fix does not mean a deployment is fixed.

## Affected components
- Go github.com/zalando/skipper: affected < 0.27.26; fixed in 0.27.26

## Suggested inspection (read-only)
- Go github.com/zalando/skipper: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on github.com/zalando/skipper.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-8qqm-fp2q-v734 (GitHub-reviewed advisory GHSA-8qqm-fp2q-v734 lists affected ranges: Go github.com/zalando/skipper >=0 <0.27.26)

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