CVE-2021-43557

Name: CVE-2021-43557
Creator: NVD / NIST
Published: 2021-11-22T09:15:07.627+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

HIGHCVSS 7.5/10EPSS 14.59%

Last modified Jun 17, 2026

CVE-2021-43557 is a high-severity vulnerability rated 7.5/10 on the CVSS scale. 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. EPSS estimates a 14.59% chance of exploitation in the next 30 days.

Description

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.

Metrics

CVSS 3.1

7.5/10

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

EPSS Probability

14.59%

96.2th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-77

Affected Software

Vendor	Product	Versions
Apache	Apisix	< 2.10.2

References

http://www.openwall.com/lists/oss-security/2021/11/22/1Mailing List, Third Party Advisory
http://www.openwall.com/lists/oss-security/2021/11/22/2Mailing List, Third Party Advisory
http://www.openwall.com/lists/oss-security/2021/11/23/1Exploit, Mailing List, Third Party Advisory
https://lists.apache.org/thread/18jyd458ptocr31rnkjs71w4h366mv7hExploit, Mailing List, Vendor Advisory
http://www.openwall.com/lists/oss-security/2021/11/22/1Mailing List, Third Party Advisory
http://www.openwall.com/lists/oss-security/2021/11/22/2Mailing List, Third Party Advisory
http://www.openwall.com/lists/oss-security/2021/11/23/1Exploit, Mailing List, Third Party Advisory
https://lists.apache.org/thread/18jyd458ptocr31rnkjs71w4h366mv7hExploit, Mailing List, Vendor Advisory

Timeline

Published: Nov 22, 2021
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2021-43557?

How severe is CVE-2021-43557?

CVE-2021-43557 has a CVSS score of 7.5/10 (HIGH severity). The EPSS model estimates a 14.59% probability of exploitation in the next 30 days.

How do I fix CVE-2021-43557?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

Are you affected by CVE-2021-43557?

Run a free Strix scan to check your systems for this vulnerability.

Scan your code now

Source: NVD / NIST