#875 Hang with actionsfile rule with backreference

Privoxy version: 3.0.21
Operating system: Windows 7 SP1 64-bit

Using a minimal configuration and a single actions file rule with backreferencing:
{+block{Crashes Privoxy}}
/([a-z])\1

Privoxy hangs when trying to access a matching URL ( http://example/aa ) or the Privoxy URL lookup page for a matching URL. Attached are the config used, sample actions file and log files. I have also generated a crash dump of the process which can be supplied if it will be helpful.

[Fabian Keil]

Thanks for the report.

This may be a Windows-only issue, at least I can't reproduce the problem
on FreeBSD and get the expected error message:
"error compiling /([a-z])\1 from /([a-z])\1: bad back reference at offset 11".

Back references are disabled in compile_pattern(), removing the REG_NOSUB
flag should enable them.

[Fabian Keil]

Is this still an issue with Privoxy 3.0.24.

[Lee]

yes - still an issue with Privoxy 3.0.26

[Lee]

On Fri, Apr 10, 2026 at 5:19 AM Fabian Keil fabiankeil@users.sourceforge.net wrote:

• assigned_to: Fabian Keil
• Comment:

Does anyone know if this got fixed by the switch to PCRE2?

I don't know if it was every fixed. But I'd close anything that dates back
to 2016 with a note to open a new ticket if it's still happening.

Regards
Lee

[Fabian Keil]

Does anyone know if this got fixed by the switch to PCRE2?