[squid-users] FATAL: invalid pct-encoded triplet

[Amos Jeffries]

On 06/02/2026 03:44, Andrea Venturoli wrote:
> Hello.
> 
> Running Squid 7.3 on several boxes.
> In the last couple of days it has been crashing on one.
> 
> Last time I captured this in the logs:
>> 2026/02/05 15:22:10 kid1| WARNING: dns-mime-type ACL is used in 
>> context without an HTTP response. Assuming mismatch.
>>     current master transaction: master72

As the message says The ACL you have named "dns-mime-type" is being 
checked when there is no HTTP Response. I assume from the name that it 
needs the mime type, which comes from an HTTP Response header.

Squid copes with these by assuming a mis-match or skipping the access rule.

This is a flaw in your security policy which you should fix, maybe minor 
or maybe serious - hard to tell without full knowledge of that policy 
and reasons for it.


>> 2026/02/05 15:22:10 kid1| FATAL: invalid pct-encoded triplet
>>     exception location: Uri.cc(102) Decode
>>     current master transaction: master72

This is likely bug 5501.

"
The bug affects url_regex and urllogin ACLs. However, not every use of
those ACLs results in a FATAL exit. The exact preconditions are unknown.
"

I have initiated a backport for the fix to v7.
You can find the patch at <https://github.com/squid-cache/squid/pull/2369>


>> 2026/02/05 15:22:10| Removing PID file (/var/run/squid/squid.pid)
> 
> The first two lines are quite common.
> I searched for the subsequent messages, which seem to be the interesting 
> ones, but found nothing.
> 
> I'll try to upgrade to 7.4 and possibly get a core dump, but if someone 
> has any hint in the meantime...
> 

7.4 will not help with this particular issue. Though upgrade is usually 
worthwhile anyway.


HTH
Amos