Dropbox apt infrastructure relying on unsecure SHA1

Hey prahal, thanks for bringing this to our attention.

I've gone ahead and reached out to our team about it, and I'll get back to you with more info, when I have it.

Thanks in advance for your patience!

recently I found a workaround : just "borrow" the new keyring from dropbox fedora.

curl -s https://linux.dropbox.com/fedora/rpm-public-key.asc | sudo tee /usr/share/keyrings/dropbox.asc > /dev/null

Then update your source list (typically at /etc/apt/sources.list.d/dropbox.list) to use those keyring.

Types: deb
URIs: http://linux.dropbox.com/debian/
Suites: trixie
Components: main
Signed-By: /usr/share/keyrings/dropbox.asc

Now you'll be able to update the Dropbox into the recent version.

Thanks for bringing this issue to our attention, I've forwarded this issue to the team to take a look. I don't have any information on next steps or timeline at this moment but will update the thread when I hear back.

curl -s https://linux.dropbox.com/fedora/rpm-public-key.asc | sudo tee /usr/share/keyrings/dropbox.asc > /dev/null

It's worth noting: Many guides mention using `gpg --dearmor <key>` on `dropbox.asc`.

This then creates `dropbox.gpg`, and it doesn't work, because the SHA2 signature is apparently removed.

(You can check this by using `gpg --list-packets dropbox.asc`

which will show:

# off=0 ctb=99 tag=6 hlen=3 plen=269
:public key packet:
        version 4, algo 1, created 1265928625, expires 0
        pkey[0]: [2048 bits]
        pkey[1]: [17 bits]
        keyid: FC918B335044912E
# off=272 ctb=b4 tag=13 hlen=2 plen=49
:user ID packet: "Dropbox Automatic Signing Key <linux@dropbox.com>"
# off=323 ctb=89 tag=2 hlen=3 plen=310
:signature packet: algo 1, keyid FC918B335044912E
        version 4, created 1265928625, md5len 0, sigclass 0x13
        digest algo 2, begin of digest 2f f3
        hashed subpkt 2 len 4 (sig created 2010-02-11)
        hashed subpkt 27 len 1 (key flags: 03)
        hashed subpkt 11 len 5 (pref-sym-algos: 9 8 7 3 2)
        hashed subpkt 21 len 3 (pref-hash-algos: 2 8 3)
        hashed subpkt 22 len 3 (pref-zip-algos: 2 3 1)
        hashed subpkt 30 len 1 (features: 01)
        hashed subpkt 23 len 1 (keyserver preferences: 80)
        subpkt 16 len 8 (issuer key ID FC918B335044912E)
        data: [2044 bits]
# off=636 ctb=89 tag=2 hlen=3 plen=401
:signature packet: algo 1, keyid FC918B335044912E
        version 4, created 1766521393, md5len 0, sigclass 0x13
        digest algo 8, begin of digest c2 de
        critical hashed subpkt 2 len 4 (sig created 2025-12-23)
        hashed subpkt 11 len 3 (pref-sym-algos: 9 8 7)
        hashed subpkt 16 len 8 (issuer key ID FC918B335044912E)
        hashed subpkt 20 len 70 (notation: salt@notations.sequoia-pgp.org=[not human readable])
        hashed subpkt 21 len 1 (pref-hash-algos: 8)
        hashed subpkt 22 len 3 (pref-zip-algos: 2 3 1)
        hashed subpkt 23 len 1 (keyserver preferences: 80)
        hashed subpkt 27 len 1 (key flags: 03)
        hashed subpkt 30 len 1 (features: 01)
        hashed subpkt 33 len 21 (issuer fpr v4 1C61A2656FB57B7E4DE0F4C1FC918B335044912E)
        data: [2047 bits]

On line 12, you'll note `digest algo 2` - which translates to SHA1. (I assume `digest algo 1 is md5, but 🤷‍♂️)

Line 25 has `digest algo 8` indicates SHA256, and `digest algo 10` indicates SHA512.

If you do the `gpg --dearmor` step, the second signature packet is removed (at least with the default options).

The workaround worked for me as well on debian 13.3 "trixie", amd64.

Here is what I did

Found that /etc/apt/sources.list.d/dropbox.list had signed-by=/etc/apt/keyrings/dropbox.asc

deb [arch=i386,amd64 signed-by=/etc/apt/keyrings/dropbox.asc] http://linux.dropbox.com/debian trixie main

Moved away existing /etc/apt/keyrings/dropbox.asc

mv /etc/apt/keyrings/dropbox.asc /etc/apt/keyrings/dropbox.asc.backup

Downloaded the fedora signing key and put it in the place of the old dropbox.asc

curl -s https://linux.dropbox.com/fedora/rpm-public-key.asc  >/etc/apt/keyrings/dropbox.asc

Tried "apt update" which now ran without error messages                                                                 

root@marquez:~# apt update
Hit:1 http://deb.debian.org/debian stable-backports InRelease
Hit:2 http://security.debian.org/debian-security stable-security InRelease
Ign:3 https://repo.vivaldi.com/stable/deb stable InRelease
Hit:4 https://repo.vivaldi.com/stable/deb stable Release
Hit:6 https://ftp.postgresql.org/pub/pgadmin/pgadmin4/apt/bullseye pgadmin4 InRelease
Hit:7 http://ftp.no.debian.org/debian stable InRelease
Hit:8 http://ftp.no.debian.org/debian stable-updates InRelease
Hit:9 https://dbeaver.io/debs/dbeaver-ce  InRelease
Hit:10 http://linux.dropbox.com/debian trixie InRelease
All packages are up to date.
root@marquez:~#

Neal​ your fix worked. Indeed from https://www.dropbox.com/fr/install-linux I reinstalled the Ubuntu 22.10 and newer deb (24th of March 2026) on Debian Forky and this issue about obsolete SHA1 apt repo is fixed.

(the current deb is 

https://www.dropbox.com/download?dl=packages/ubuntu/dropbox_2026.01.15_amd64.deb)