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ApisixApplication · Apache

CVE-2021-43557

HIGH · 7.5 CVSS v3.1 Published 2021-11-22
Fix available
A fix is available. Upgrade to 2.10.2 or later.
See remediation →
84/100
Remediation priority · High
Public exploit 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
The uri-block plugin in Apache APISIX before 2.10.2 uses $request_uri without verification. The $request_uri is the full original request URI without normalization. This makes it possible to construct a URI to bypass the block list on some occasions. For instance, when the block list contains "^/internal/", a URI like `//internal/` can be used to bypass it. Some other plugins also have the same issue. And it may affect the developer's custom plugin.

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
How this class of weakness works · CWE-77

User input reaches a command interpreter without being fully separated from the command itself, so an attacker can append instructions of their own. Because those run with the application's privileges, it frequently means control of the host. The lasting fix is to avoid constructing commands from input — call APIs directly and pass arguments as data, never as concatenated strings.

General guidance for the command injection class — the official description and references above are authoritative for this specific CVE. Want a bespoke review and a reviewed fix? Ask our team →

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
ApisixApplication
Affected:< 2.10.2

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
None
Availability
None

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

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 2.10.2 or later
Fixed in 2.10.2
Recommended fix High confidence

2.10.2

  1. 1. Identify the current Apache APISIX version by checking the installed version or running 'apisix version'
  2. 2. Back up all Apache APISIX configurations, including the conf/config.yaml file and any custom plugin configurations
  3. 3. Review the Apache APISIX 2.10.2 release notes for any configuration changes or migration requirements
  4. 4. Upgrade Apache APISIX to version 2.10.2 or later using the appropriate package manager or build method (e.g., 'yum upgrade apisix' or 'apt-get upgrade apisix' for package installations, or rebuild from source)
  5. 5. After upgrade, restart the APISIX service (e.g., 'apisix restart' or 'systemctl restart apisix')
  6. 6. Verify the uri-block plugin is working correctly by testing blocked URIs including normalized forms like '//internal/' against block rules such as '^/internal/'
  7. 7. Check that other plugins using $request_uri are functioning as expected after the upgrade
Caveat Review Apache APISIX 2.10.2 release notes for any breaking changes from your current version; major version upgrades may include configuration schema changes

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

We can perform the upgrade in your staging environment and verify nothing breaks — typical engagement from $3,200. Get the upgrade done

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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-2021-43557 in production — separate from our analysis above.

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