CVE-2021-43557Public exploitNetwork attack vector

Unauthenticated route access via unnormalized request paths

Published Nov 22, 2021 · Updated Aug 4, 2024

Access-control bypass in Apache APISIX before 2.10.2 allows remote attackers to reach blocked routes via crafted request paths. The uri-blocker plugin compares block rules against ctx.var.request_uri, which preserves the unnormalized original path, while routing normalizes it. Exploitation requires a route protected by uri-blocker or another affected custom plugin, and successful requests reach otherwise forbidden upstream content.

CVSS severity7.5
High
EPSS probability12.94%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Access-control bypass in Apache APISIX before 2.10.2 allows remote attackers to reach blocked routes via crafted request paths. The uri-blocker plugin compares block rules against ctx.var.request_uri, which preserves the unnormalized original path, while routing normalizes it. Exploitation requires a route protected by uri-blocker or another affected custom plugin, and successful requests reach otherwise forbidden upstream content.

The record

CVE
CVE-2021-43557
Published
Nov 22, 2021
Updated
Aug 4, 2024
Vendor
The Apache Software Foundation
Product
Apache APISIX
Classifications
CWE-77, T1190
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Nov 22, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 4, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=1.5 <Apache APISIX 1.5*

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

The Apache Software Foundation · Apache APISIXversion=1.5 <Apache APISIX 1.5*

Published CVSS scores

5.0NIST National Vulnerability DatabaseAV:N/AC:L/Au:N/C:P/I:N/A:N
7.5NIST National Vulnerability DatabaseCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-77Improper Neutralization of Special Elements used in a Command ('Command Injection')
T1190Exploit Public-Facing Application

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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