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Traffic ServerApplication · Apache

CVE-2021-35474

CRITICAL · 9.8 CVSS v3.1 Published 2021-06-30
Fix available
A fix is available. Upgrade to after 9.0.1 or later.
See remediation →
100/100
Remediation priority · Urgent
Remotely reachable No privileges Zero-click

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
Stack-based Buffer Overflow vulnerability in cachekey plugin of Apache Traffic Server. This issue affects Apache Traffic Server 7.0.0 to 7.1.12, 8.0.0 to 8.1.1, 9.0.0 to 9.0.1.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

A stack-based buffer overflow vulnerability exists in the cachekey plugin of Apache Traffic Server. An attacker could exploit this by sending specially crafted requests to the cachekey plugin, potentially leading to remote code execution or denial of service. This affects versions 7.0.0 through 7.1.12, 8.0.0 through 8.1.1, and 9.0.0 through 9.1.0.

MitigationUpgrade Apache Traffic Server to a patched version beyond 9.1.0, or disable the cachekey plugin if an immediate upgrade is not feasible.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
Traffic ServerApplication
Affected:>= 7.0.0, <= 7.1.12>= 8.0.0, <= 8.1.1>= 9.0.0, <= 9.0.1
Debian LinuxOperating system
Affected:= 10.0

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

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

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Identify Apache Traffic Server installation
    Run 'traffic_server -V' or check the package manager for the installed version (e.g., dpkg -l | grep traffic-server on Debian)
    Affected if The installed version falls within 7.0.0 to 7.1.12, 8.0.0 to 8.1.1, or 9.0.0 to 9.1.0
  2. Determine if cachekey plugin is loaded
    Examine the plugin configuration in records.config or look for cachekey.so in the plugin directory specified in plugin.config. Check if 'cachekey' appears in the enabled plugin list.
    Affected if The cachekey plugin is enabled and loaded by Traffic Server
  3. Verify cachekey plugin configuration
    Review the cachekey plugin configuration files for any user-controlled input patterns that could trigger the buffer overflow during request processing.
    Affected if The cachekey plugin has active URI capture groups or variable mappings that process incoming request URIs

A user is affected if they are running a vulnerable Apache Traffic Server version (7.x through 9.1.0) with the cachekey plugin enabled and actively processing requests.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Upgrade available Upgrade to a release after 9.0.1
Interim mitigation

Upgrade Apache Traffic Server to a patched version beyond 9.1.0, or disable the cachekey plugin if an immediate upgrade is not feasible.

Recommended fix Moderate confidence

Apache Traffic Server 7.2.0, 8.1.2, or 9.0.2 (or later stable releases within each major branch)

  1. 1. Identify the currently installed Apache Traffic Server version using: traffic_server -version or ats -version
  2. 2. For Debian 10.0 systems, check if the system has received the security update via: apt-get update && apt-get upgrade traffic-server
  3. 3. If running a vulnerable version (7.0.0-7.1.12, 8.0.0-8.1.1, or 9.0.0-9.0.1), plan for an upgrade to a fixed version
  4. 4. Before upgrading in production, review the Apache Traffic Server upgrade documentation and test in a staging environment
  5. 5. Back up the current configuration files in /etc/trafficserver/ before upgrading
  6. 6. Perform the upgrade using the package manager: apt-get update && apt-get install traffic-server (Debian) or the appropriate method for your distribution
  7. 7. After upgrade, verify the new version is installed: traffic_server -version
  8. 8. Validate that the cachekey plugin functions correctly with your existing configuration
Caveat Review release notes for configuration changes between versions; minor version upgrades within the same major version typically have low breaking-change risk

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Traffic Server Scoped from the published advisory
  • Consultation2.0 h
  • Implementation4.0 h
  • Testing6.0 h
  • Review / QA3.0 h
15.0 hours of engineering $2,560
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2021-35474 in production — separate from our analysis above.

No notes yet

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data