Synopsis: Low: httpd security, bug fix, and enhancement update
Advisory ID: SLSA-2015:1249-2
Issue Date: 2015-07-22
CVE Numbers: CVE-2013-5704
A flaw was found in the way httpd handled HTTP Trailer headers when
processing requests using chunked encoding. A malicious client could use
Trailer headers to set additional HTTP headers after header processing was
performed by other modules. This could, for example, lead to a bypass of
header restrictions defined with mod_headers. (CVE-2013-5704)
This update also fixes the following bugs:
* The order of mod_proxy workers was not checked when httpd configuration
was reloaded. When mod_proxy workers were removed, added, or their order
was changed, their parameters and scores could become mixed. The order of
mod_proxy workers has been made internally consistent during configuration
* The local host certificate created during firstboot contained CA
extensions, which caused the httpd service to return warning messages.
This has been addressed by local host certificates being generated with
the “-extensions v3_req” option.
* The default mod_ssl configuration no longer enables support for SSL
cipher suites using the single DES, IDEA, or SEED encryption algorithms.
* The apachectl script did not take into account the HTTPD_LANG variable
set in the /etc/sysconfig/httpd file during graceful restarts.
Consequently, httpd did not use a changed value of HTTPD_LANG when the
daemon was restarted gracefully. The script has been fixed to handle the
HTTPD_LANG variable correctly.
* The mod_deflate module failed to check the original file size while
extracting files larger than 4 GB, making it impossible to extract large
files. Now, mod_deflate checks the original file size properly according
to RFC1952, and it is able to decompress files larger than 4 GB.
* The httpd service did not check configuration before restart. When a
configuration contained an error, an attempt to restart httpd gracefully
failed. Now, httpd checks configuration before restart and if the
configuration is in an inconsistent state, an error message is printed,
httpd is not stopped and a restart is not performed.
* The SSL_CLIENT_VERIFY environment variable was incorrectly handled when
the “SSLVerifyClient optional_no_ca” and “SSLSessionCache” options were
used. When an SSL session was resumed, the SSL_CLIENT_VERIFY value was set
to “SUCCESS” instead of the previously set “GENEROUS”. SSL_CLIENT_VERIFY
is now correctly set to GENEROUS in this scenario.
* The ab utility did not correctly handle situations when an SSL
connection was closed after some data had already been read. As a
consequence, ab did not work correctly with SSL servers and printed “SSL
read failed” error messages. With this update, ab works as expected with
* When a client presented a revoked certificate, log entries were created
only at the debug level. The log level of messages regarding a revoked
certificate has been increased to INFO, and administrators are now
properly informed of this situation.
In addition, this update adds the following enhancement:
* A mod_proxy worker can now be set into drain mode (N) using the
balancer-manager web interface or using the httpd configuration file. A
worker in drain mode accepts only existing sticky sessions destined for
itself and ignores all other requests. The worker waits until all clients
currently connected to this worker complete their work before the worker
is stopped. As a result, drain mode enables to perform maintenance on a
worker without affecting clients.
After installing the updated packages, the httpd service will be restarted
– Scientific Linux Development Team