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CVE-2026-65838 high CVSS 8.2

Vulnerability in github.com/zalando/skipper (CVE-2026-65838)

Summary

Vulnerability in github.com/zalando/skipper (CVE-2026-65838). Confidential information can be exposed externally. Exploitable via parsed_body. Mitigation: upgrade to 0.27.26 or later.

Original description

The description as published by the source.

Summary

A wrong policy can be an open door.
You have to check input.attributes.request.http.truncated_body in your policy.

Description

Incomplete fix for CVE-2026-50197: an oversized declared-Content-Length body still hands OPA an empty parsed_body, 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
parsed_body, while the full forbidden payload still flows to the upstream. A deny-on-presence policy
(default allow = true; allow = false if input.parsed_body.) — the exact Rego shape the
advisory describes — fails OPEN. The fix's own comment reasons only about ContentLength == -1; the
oversized branch was never considered, and the added PoC test only covers small bodies.

Affected code

  • filters/openpolicyagent/openpolicyagent.go ExtractHttpBodyOptionally: the
    expectedSize <= maxBodyBytes gate lets an oversized declared body fall through to
    return req.Body, nil, func() {}, nil (OPA sees an empty document).
  • Corroborated by Skipper's own unit test "Read body exhausting max bytes" (`{ "welco…

Source: NIST National Vulnerability Database NVD GitHub Advisory

Auto-generated summary

Assembled by SecPulse from the source data (CVSS, CWE, affected versions) using templates — no AI involved. Check the original description and references below for exact details.

A vulnerability tracked as CVE-2026-65838 has been found in github.com/zalando/skipper.
Attackers can target a specific entry point like parsed_body over the network to misuse the product.
Confidential information can be exposed externally. CVSS score: 8.2/10.
What to do: upgrade github.com/zalando/skipper to 0.27.26 or later.
If unsure, ask your IT team or search "github.com/zalando/skipper CVE-2026-65838" on the vendor's site.

CVE-2026-65838 (github.com/zalando/skipper) — CWE-444 / CVSS v3 8.2
Attack vector: remote (network-reachable) / unauthenticated / no user interaction
Attack surface: parsed_body / maxBodyBytes / ExtractHttpBodyOptionally / golang
Patched: 0.27.26 — apply immediately
Plan: 1) Audit SBOM/dependencies, 2) Stage→prod upgrade, 3) Add WAF/proxy monitoring on affected endpoints, 4) Hunt IOCs in logs.
Refs: see the GHSA / vendor advisory / patched release linked on this page.

❓ What is the problem

A vulnerability (CWE-444) exists in github.com/zalando/skipper. Attackers reach the vulnerable code path via parsed_body without authentication.

📍 Affected scope

Check the vendor advisory for the affected versions of github.com/zalando/skipper. Attack surface: parsed_body / maxBodyBytes / ExtractHttpBodyOptionally / golang.

🔥 Severity

Severity: High (CVSS 8.2/10). Confidential information can be exposed externally.

🔧 How to fix

Update to 0.27.26.

🛡️ Workaround

Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.

🔍 Detection

Search webserver/proxy logs for unusual request patterns matching this CVE's known IOCs. Run grep -r 'github.com/zalando/skipper' . against your dependency files (package-lock.json, requirements.txt, go.sum) to find affected services.

Response actions

Concrete steps and command examples for SOC/SRE teams to execute in order

  1. 1
    Identify exposure identify 
    grep -r 'github.com/zalando/skipper' . | grep -v node_modules

    リポジトリと本番環境の依存ファイル (package-lock.json / requirements.txt / go.sum / Gemfile.lock 等) で github.com/zalando/skipper を grep し、稼働しているサービス・バージョンを把握する。

  2. 2
    Apply patch patch 
    Upgrade github.com/zalando/skipper to 0.27.26

    ステージング環境で 0.27.26 に上げて回帰テスト → 本番反映。回帰テストはアプリの主要ハッピーパスを含めること。

  3. 3
    Post-deployment verification verify 
    Confirm patched version is live in production

    パッチ適用後、ステージングで PoC または同等の悪用パターンを再現して脆弱性が閉じたことを確認。本番ではアクセスログ・WAF でアラート再発が無いか継続監視。

Affected packages

go github.com/zalando/skipper
[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"0.27.26"}]}]

References

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