Debian 12 weird ipv6 breaks internet access

I've set up a fresh Debian 12 system today and wanted to try out IPv6 in my network a bit. So I set up an IPv6 ULA on my router and created a new Debian VM for testing. The Debian VM picks up the ULA address through SLAAC just fine, but it also generates a strange and seemingly incorrect IPv6 address alongside it, one that appears to be just the EUI-64 interface identifier without any of the network prefix bits set. The output of ip address looks like this:

inet6 ::be24:11ff:fe59:4e73/64 scope global
   valid_lft 2591891sec preferred_lft 604691sec
inet6 fdf2:e2f0:3d5b:0:be24:11ff:fe59:4e73/64 scope global deprecated dynamic mngtmpaddr
   valid_lft 2591893sec preferred_lft 0sec
inet6 fdf2:e2f0:3d5b:1:be24:11ff:fe59:4e73/64 scope global dynamic mngtmpaddr
   valid_lft 2591893sec preferred_lft 604693sec
inet6 fe80::be24:11ff:fe59:4e73/64 scope link
   valid_lft forever preferred_lft forever

Although the ULA address is generated just fine, this non-routable address :be24:11ff:fe59:4e73/64 breaks my internet access as its used as the source IP of ping or curl for example. Output of rdisk6

Soliciting ff02::2 (ff02::2) on eth0...

Hop limit                 :    undefined (      0x00)
Stateful address conf.    :          Yes
Stateful other conf.      :           No
Mobile home agent         :           No
Router preference         :       medium
Neighbor discovery proxy  :           No
Router lifetime           :         1800 (0x00000708) seconds
Reachable time            :  unspecified (0x00000000)
Retransmit time           :  unspecified (0x00000000)
 Source link-layer address: 78:9A:18:94:4A:B4
 Recursive DNS server     : fdf2:e2f0:3d5b:1:be24:11ff:fe59:4e73
 Recursive DNS server     : fdf2:e2f0:3d5b:1:be24:11ff:feb6:90f
  DNS servers lifetime    :         1800 (0x00000708) seconds
 Prefix                   : fdf2:e2f0:3d5b:1::/64
  On-link                 :          Yes
  Autonomous address conf.:          Yes
  Valid time              :      2592000 (0x00278d00) seconds
  Pref. time              :       604800 (0x00093a80) seconds
 Prefix                   : fdf2:e2f0:3d5b::/64
  On-link                 :          Yes
  Autonomous address conf.:          Yes
  Valid time              :      2592000 (0x00278d00) seconds
  Pref. time              :            0 (0x00000000) seconds
 from fe80::7a9a:18ff:fe94:4ab4

Router address setup:

[gateway] > /ipv6/address/print detail  
Flags: X - disabled, I - invalid, D - dynamic; G - global, L - link-local; S - slave; d - deprecated 
 1  G   address=fdf2:e2f0:3d5b:1::/64 from-pool=private-pool interface= VLAN010 actual-interface=VLAN010 eui-64=no advertise=yes no-dad=no 
 
[gateway] > /ipv6/nd/print 
Flags: X - disabled, I - invalid; * - default 
 0  * interface=all ra-interval=3m20s-10m ra-delay=3s mtu=unspecified reachable-time=unspecified retransmit-interval=unspecified ra-lifetime=30m ra-preference=medium hop-limit=unspecified advertise-mac-address=yes advertise-dns=yes 
      managed-address-configuration=yes other-configuration=no dns=fdf2:e2f0:3d5b:1:be24:11ff:fe59:4e73,fdf2:e2f0:3d5b:1:be24:11ff:feb6:90f

Does anyone know why this address is being generated and how I can disable it?