V84.0.140, downgrade no longer possible?

[avayax]

Did I read this correctly, new firmware T23-44.84.0.140.rom no longer allows downgrading of firmware?
So in order to downgrade I have to factory reset or does it no longer work at all?

Why was this implemented?

[Yisroel_MongoTEL]

You obviously read correctly, the release notes say:

Quote:Optimized the upgrade mechanism. You are not allowed to downgrade the phone from current firmware to the previous one.

You will probably not get an answer as to why it was needed.

The only way to downgrade, I assume, would be with a TFTP recovery flash.

[avayax]

Good to know, cause then I will never upgrade to 84.0.140.
This makes no sense.

[emaktech]

We just attempted to perform a TFTP recovery on a T23G on 44.84.0.140 and it is also failing. Unfortunately in our current situation for this phone, this has led to it being bricked, it's now in the trash.

Yealink current v85 firmwares are broken, and Yealink frequently breaks things when they upgrade to newer firmwares that necessitates downgrades. Now testing later firmwares isn't possible since if bugs are discovered, there is no rollback.

DO NOT UPGRADE TO V84.0.140, DOWNGRADE IS IMPOSSIBLE IF NECESSARY

Sorry Yealink, it's been nice working with you. After >2000 endpoints deployed, I think it's time to pursue other vendor options...

[complex1]

@emaktech

Question:
Where are Release Notes for?
Didn't you read those before any firmware upgrade?
It clearly states that you are not allowed to downgrade the phone from current firmware to the previous one, because of "Optimized the upgrade mechanism".
So, is this Yealinks' fault? I personally don't think so. There is no one to force you to upgrade.

[avayax]

But who would have thought that you are not even able to downgrade via tftp recovery.
This makes no sense.

[emaktech]

(01-09-2021 03:39 AM)complex1 Wrote:  @emaktech

Question:
Where are Release Notes for?
Didn't you read those before any firmware upgrade?
It clearly states that you are not allowed to downgrade the phone from current firmware to the previous one, because of "Optimized the upgrade mechanism".
So, is this Yealinks' fault? I personally don't think so. There is no one to force you to upgrade.

If you must know, one of our technicians while onsite onboarding a customer encountered a phone that was carrier locked (e.g. factory reset was password locked). So our tech attempted to do a tftp recovery which used to remove the reset lock. In doing this, they followed our usual procedure which was to use our internal recovery files and simply downloading firmware from Yealink's websites. When that didn't work, we though we would try to downgrade to an older firmware figuring that tftp unlock method didn't work on later firmwares which is when we found out it was now impossible to downgrade the phone. Ergo this phone is now a paperwight and was thrown away.

Do I care about this particular event? Really no, we simply sold the user another phone.

What matters to me is that this makes me very fearful as to whether Yealink has been forced into putting back doors or otherwise into their software for shall we say "regulatory compliance" reasons.

There is no logical explanation as to why a manufacturer would make it impossible to downgrade a firmware. That's a very big step to take and there has to be a very strong reason to do it. Something is very fishy about this change, and if I'm thinking this now, there will probably be more people questioning this over time. We sell 95% Yealink products as it stands, so this could become a huge risk to our business which is why going forward we will need to validate other vendor products and consider moving to them as our primary endpoints.

[Yisroel_MongoTEL]

They don't have this for most other phones, so your conspiracy-theory about backdoors doesn't make sense.

The lack of technical communication from Yealink is indeed frustrating. If they made such tough restriction at least say why! But communication is not a new issue from them

It perfectly makes technical sense that an upgraded that changes something major low level in the firmware results in a restriction not to downgrade. I've seen it with other manufacturers as well (Fanvil Doorbells are a recent one that come to mind.)

[avayax]

(01-12-2021 01:55 AM)Yisroel_MongoTEL Wrote:  They don't have this for most other phones, so your conspiracy-theory about backdoors doesn't make sense.

The lack of technical communication from Yealink is indeed frustrating. If they made such tough restriction at least say why! But communication is not a new issue from them

It perfectly makes technical sense that an upgraded that changes something major low level in the firmware results in a restriction not to downgrade. I've seen it with other manufacturers as well (Fanvil Doorbells are a recent one that come to mind.)

But what is the major change in .140 that warrants blocking firmware downgrades?
Besides these T23G phones do not seem to get V85 firmware upgrades, so my guess is they're going eol?