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CVE-2020-1938

Published: 24 February 2020

When using the Apache JServ Protocol (AJP), care must be taken when trusting incoming connections to Apache Tomcat. Tomcat treats AJP connections as having higher trust than, for example, a similar HTTP connection. If such connections are available to an attacker, they can be exploited in ways that may be surprising. In Apache Tomcat 9.0.0.M1 to 9.0.0.30, 8.5.0 to 8.5.50 and 7.0.0 to 7.0.99, Tomcat shipped with an AJP Connector enabled by default that listened on all configured IP addresses. It was expected (and recommended in the security guide) that this Connector would be disabled if not required. This vulnerability report identified a mechanism that allowed: - returning arbitrary files from anywhere in the web application - processing any file in the web application as a JSP Further, if the web application allowed file upload and stored those files within the web application (or the attacker was able to control the content of the web application by some other means) then this, along with the ability to process a file as a JSP, made remote code execution possible. It is important to note that mitigation is only required if an AJP port is accessible to untrusted users. Users wishing to take a defence-in-depth approach and block the vector that permits returning arbitrary files and execution as JSP may upgrade to Apache Tomcat 9.0.31, 8.5.51 or 7.0.100 or later. A number of changes were made to the default AJP Connector configuration in 9.0.31 to harden the default configuration. It is likely that users upgrading to 9.0.31, 8.5.51 or 7.0.100 or later will need to make small changes to their configurations.

Notes

AuthorNote
mdeslaur
In Ubuntu packages, the AJP connector is disabled by default,
so unless specifically enabled by an admin, deployments made
using the package are not vulnerable to this issue.

One of the upstream fixes for this issue renames the
requiredSecret parameter to secret and adds a secretRequired
parameter that defaults to "true". Adding this change to stable
releases will result in servers failing to start until the
administrator either changes secretRequired to "false", or
configures an adequate secret. Apache starting supporting a
secret in mod_proxy_ajp starting with 2.4.42, which means to
enable a secret we will have to issue Apache updates with
the backported secret support.

Mitigation

mdeslaur> In environments where the AJP connector is enabled, care should
mdeslaur> be taken to not expose the AJP port to attackers, either by
mdeslaur> using a firewall to block the AJP port, or by binding it to
mdeslaur> localhost by using address="127.0.0.1" in the AJP configuration.

Priority

Low

Cvss 3 Severity Score

9.8

Score breakdown

Status

Package Release Status
tomcat7
Launchpad, Ubuntu, Debian
bionic Ignored
(not vulnerable by default)
eoan Does not exist

focal Does not exist

groovy Does not exist

hirsute Does not exist

impish Does not exist

jammy Does not exist

kinetic Does not exist

lunar Does not exist

mantic Does not exist

noble Does not exist

trusty Ignored

upstream Needs triage

xenial Ignored
(not vulnerable by default)
Patches:
upstream: https://github.com/apache/tomcat/commit/0d633e72ebc7b3c242d0081c23bba5e4dacd9b72
upstream: https://github.com/apache/tomcat/commit/40d5d93bd284033cf4a1f77f5492444f83d803e2
upstream: https://github.com/apache/tomcat/commit/b99fba5bd796d876ea536e83299603443842feba
upstream: https://github.com/apache/tomcat/commit/f7180bafc74cb1250c9e9287b68a230f0e1f4645










tomcat8
Launchpad, Ubuntu, Debian
bionic Ignored
(not vulnerable by default)
eoan Does not exist

focal Does not exist

groovy Does not exist

hirsute Does not exist

impish Does not exist

jammy Does not exist

kinetic Does not exist

lunar Does not exist

mantic Does not exist

noble Does not exist

trusty Does not exist

upstream Needs triage

xenial Ignored
(not vulnerable by default)
Patches:




upstream: https://github.com/apache/tomcat/commit/69c56080fb3355507e1b55d014ec0ee6767a6150
upstream: https://github.com/apache/tomcat/commit/b962835f98b905286b78c414d5aaec2d0e711f75
upstream: https://github.com/apache/tomcat/commit/9be57601efb8a81e3832feb0dd60b1eb9d2b61d5
upstream: https://github.com/apache/tomcat/commit/64159aa1d7cdc2c118fcb5eac098e70129d54a19
upstream: https://github.com/apache/tomcat/commit/03c436126db6794db5277a3b3d871016fb9a3f23





tomcat9
Launchpad, Ubuntu, Debian
bionic Ignored
(not vulnerable by default)
eoan Ignored
(end of life)
focal Not vulnerable
(9.0.31-1)
groovy Not vulnerable
(9.0.31-1)
hirsute Not vulnerable
(9.0.31-1)
impish Not vulnerable
(9.0.31-1)
jammy Not vulnerable
(9.0.31-1)
kinetic Not vulnerable
(9.0.31-1)
lunar Not vulnerable
(9.0.31-1)
mantic Not vulnerable
(9.0.31-1)
noble Not vulnerable
(9.0.31-1)
trusty Does not exist

upstream
Released (9.0.31-1)
xenial Does not exist

Patches:









upstream: https://github.com/apache/tomcat/commit/0e8a50f0a5958744bea1fd6768c862e04d3b7e75
upstream: https://github.com/apache/tomcat/commit/9ac90532e9a7d239f90952edb229b07c80a9a3eb
upstream: https://github.com/apache/tomcat/commit/64fa5b99442589ef0bf2a7fcd71ad2bc68b35fad
upstream: https://github.com/apache/tomcat/commit/7a1406a3cd20fdd90656add6cd8f27ef8f24e957
upstream: https://github.com/apache/tomcat/commit/49ad3f954f69c6e838c8cd112ad79aa5fa8e7153

Severity score breakdown

Parameter Value
Base score 9.8
Attack vector Network
Attack complexity Low
Privileges required None
User interaction None
Scope Unchanged
Confidentiality High
Integrity impact High
Availability impact High
Vector CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H