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CVE-2026-33267 – Header Injection / Internal Metadata Spoofing – Apache Traffic Server 9.2.0–9.2….

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Summary

CVE-2026-33267 is an Improper Input Validation vulnerability in Apache Traffic Server (ATS) in which untrusted @ headers in HTTP requests can be used to spoof ATS internal metadata, affecting versions 9.2.0 through 9.2.14 and 10.1.0 through 10.1.3. The flaw carries a perfect CVSS 3.1 score of 10.0 (Critical) and is exploitable remotely by unauthenticated attackers with no user interaction required. Apache has released fixed versions 9.2.15 and 10.1.4 and recommends immediate upgrade.

Technical details

  • Root cause: Apache Traffic Server fails to properly validate @ headers in incoming HTTP requests, allowing untrusted external input to spoof internal ATS metadata fields. These internal headers are used by ATS to make routing, caching, and access-control decisions.
  • Trigger conditions: An attacker crafts an HTTP request containing malicious @ headers and sends it to a publicly accessible ATS instance. No authentication credentials or special privileges are required, and no victim interaction is necessary.
  • Attack vector: Fully network-reachable (AV:N), low attack complexity (AC:L), no privileges required (PR:N), no user interaction (UI:N) — exploitation requires only the ability to send HTTP requests to the target.
  • Impact: The vulnerability has a Changed Scope (S:C), meaning its impact extends beyond the ATS component itself to backend resources and systems the proxy fronts. The High Confidentiality impact (C:H) and High Integrity impact (I:H) indicate that successful exploitation can allow an attacker to read sensitive data in transit and manipulate routing or access decisions, potentially enabling request forgery against backend services, cache poisoning, or unauthorized access to protected resources.

Affected software

  • Apache Traffic Server 9.2.0 through 9.2.14
  • Apache Traffic Server 10.1.0 through 10.1.3

Severity

CVSS v3.1 Base Score: 10.0 (Critical)
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:N

Mitigation and recommended actions

  • Immediate: Upgrade to Apache Traffic Server 9.2.15 (for 9.2.x deployments) or 10.1.4 (for 10.1.x deployments), which contain the official fix for this vulnerability as recommended by the Apache Software Foundation.
  • If immediate patching is not feasible, restrict inbound HTTP access to ATS instances using firewall rules or network ACLs to limit exposure to trusted sources only, pending patch application.

IONIX Status

The IONIX research team is tracking ongoing exploitation attempts and recommends immediate patching. Potentially affected assets are outlined in this post.

References

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How IONIX’s External Exposure Management Platform Detects and Validates
Zero-Days to Shrink MTTR

1

Map your entire attack surface (continously)

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2

Monitor for new CVEs

Dozens of threat intel feeds using agentic technology are continuously analyzed to detect the appearance of proof-of-concept code, exploit kits, and indicators of active targeting. IONIX goes further by applying AI to proactively evaluate whether emerging vulnerabilities are likely to be exploited, even before PoCs go public.

3

Identify Potential External Exposures

Not all CVEs matter. IONIX filters vulnerabilities by asking attacker-centric questions: Can it be reached from the internet? Does it require authentication? Is it being exploited in the wild? This dramatically reduces noise and focuses teams on threats that can actually be weaponized.

4

Create Safe, Scalable Exploit Validations

IONIX transforms real-world PoCs into safe, non-intrusive test payloads that can be run in production environments without disruption. These simulations are precisely targeted to the systems that are vulnerable, ensuring rapid validation without unnecessary load.

5

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By combining context about software stack, versioning, exposure status, and reachability, IONIX ensures that only the right payloads are executed against the right assets, maximizing efficiency and minimizing risk.

6

Drive Fast and Actionable Remediation

Results are routed through integrations with ticketing, SOAR, and SIEM tools. Issues are written in plain language, bundled into remediation clusters, and prioritized based on asset criticality, exploitability, and blast radius. This shortens mean time to remediation (MTTR) and empowers teams to act with confidence.

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