Known exploited vulnerability
CVE-2021-40438
The short answer
CVE-2021-40438 affects Apache Software Foundation Apache HTTP Server and is rated critical (CVSS 9.0). CISA added it to the Known Exploited Vulnerabilities catalog on 2021-12-01: attackers are using it, so patch it first.
What it is
A crafted request uri-path can cause mod_proxy to forward the request to an origin server choosen by the remote user. This issue affects Apache HTTP Server 2.4.48 and earlier.
Weakness: CWE-918.
Severity
9.0 critical
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:H
Exploited (CISA KEV)
Yes, since Dec 1, 2021
Federal due date Dec 15, 2021
EPSS, next 30 days
100%
Higher than 100% of scored CVEs
How it can be exploited
- Attack vector
- Network
- Attack complexity
- High
- Privileges required
- None
- User interaction
- None
- Scope
- Changed
- Confidentiality impact
- High
- Integrity impact
- High
- Availability impact
- High
What CISA says to do
Apply updates per vendor instructions.
Affected products
Apache HTTP Server. NVD's record lists the exact affected versions.
References
- cert-portal.siemens.com/productcert/pdf/ssa-685781.pdf Third Party Advisory
- httpd.apache.org/security/vulnerabilities_24.html Release NotesVendor Advisory
- lists.apache.org/thread.html/r210807d0bb55f4aa6fbe1512be6bcc4dacd64e84940429fba329967a%40%3Cusers.httpd.apache.org%3E Mailing List
- lists.apache.org/thread.html/r2eb200ac1340f69aa22af61ab34780c531d110437910cb9c0ece3b37%40%3Cbugs.httpd.apache.org%3E Mailing List
- lists.apache.org/thread.html/r3925e167d5eb1c75def3750c155d753064e1d34a143028bb32910432%40%3Cusers.httpd.apache.org%3E Mailing List
- lists.apache.org/thread.html/r61fdbfc26ab170f4e6492ef3bd5197c20b862ce156e9d5a54d4b899c%40%3Cusers.httpd.apache.org%3E Mailing List
- lists.apache.org/thread.html/r82838efc5fa6fc4c73986399c9b71573589f78b31846aff5bd9b1697%40%3Cusers.httpd.apache.org%3E Mailing List
- lists.apache.org/thread.html/r82c077663f9759c7df5a6656f925b3ee4f55fcd33c889ba7cd687029%40%3Cusers.httpd.apache.org%3E Mailing List
- lists.apache.org/thread.html/rf6954e60b1c8e480678ce3d02f61b8a788997785652e9557a3265c00%40%3Cusers.httpd.apache.org%3E Mailing List
- lists.debian.org/debian-lts-announce/2021/10/msg00001.html Mailing ListThird Party Advisory
- lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/SPBR6WUYBJNACHKE65SPL7TJOHX7RHWD/ Release Notes
- lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/ZNCYSR3BXT36FFF4XTCPL3HDQK4VP45R/ Release Notes
Questions
Is CVE-2021-40438 being exploited?
Yes. CISA added CVE-2021-40438 to its Known Exploited Vulnerabilities catalog on 2021-12-01, with a federal remediation due date of 2021-12-15. CISA lists it as used in ransomware campaigns.
How do I fix CVE-2021-40438?
CISA's required action: Apply updates per vendor instructions.
From NVD, CISA KEV, FIRST EPSS and OSV.dev, checked . Status on NVD: Analyzed. The description is NVD's text, quoted as published.
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