Recently, a bug in glibc version 2.39 and older (CVE-2024-2961) was uncovered
where a buffer overflow in character set conversions *to* the
ISO-2022-CN-EXT character set.

This specific buffer overflow in glibc is exploitable through PHP,
which uses the iconv functionality in glibc to do character set
conversions. Although the bug is exploitable in the context of the PHP
Engine, the bug is not in PHP. It is also not directly exploitable
remotely.

There are numerous reports online with titles like „Mitigating the
iconv Vulnerability for PHP (CVE-2024-2961)“ or „PHP Under Attack“. These
titles are misleading as this is *not* a bug in PHP itself.

Currently there is no fix for this issue, but there is a workaround
described in GLIBC
Vulnerability on Servers Serving PHP. It explains a way how to remove
the problematic character set from glibc. Perform this procedure for every
gconv-modules-extra.conf file that is available on your system.

Additionally it is also good practice for applications to accept only
specific charsets, with an allow-list.

Some Linux distributions such as Debian, CentOS, and others, already have
published patched variants of glibc. Please upgrade as soon as
possible.

Once an update is available in glibc, updating that package on your
Linux machine will be enough to alleviate the issue. You do not need to
update PHP, as glibc is a dynamically linked library.

PHP users on Windows are not affected.

There will therefore also not be a new version of PHP for this
vulnerability.

PHP.net news & announcements

Read More