#1124283 bind9-dnsutils: nslookup (interactive) aborts with an assertion failure in libisc

Package:
bind9-dnsutils
Source:
bind9-dnsutils
Description:
Clients provided with BIND 9
Submitter:
Stephen Tordoff
Date:
2025-12-30 00:15:04 UTC
Severity:
normal
#1124283#5
Date:
2025-12-29 23:43:58 UTC
From:
To:
Dear Maintainer,

nslookup (interactive) aborts with an assertion failure in libisc
after receiving an HINFO response (e.g. from dnscrypt-proxy
AAAA-blocking).
The same response is handled correctly by dig.

nslookup
Default server: 127.0.0.1
Address: 127.0.0.1#53
Server: 127.0.0.1
Address: 127.0.0.1#5053
Non-authoritative answer:
google hinfo = "AAAA queries have been locally blocked by
dnscrypt-proxy" "Set block_ipv6 to false to disable that feature"
Address: 127.0.0.1#5053
Non-authoritative answer:
Name: google.com
Address: 142.251.36.14
google.com hinfo = "AAAA queries have been locally blocked by
dnscrypt-proxy" "Set block_ipv6 to false to disable that feature"
signal.c:97: REQUIRE(((signal) != ((void *)0) && ((const isc__magic_t
*)(signal))->magic == ((('S') << 24 | ('I') << 16 | ('G') << 8 | ('
'))))) failed, back trace
/lib/x86_64-linux-gnu/libisc-9.20.15-1~deb13u1-Debian.so(+0x3568f)
[0x7648119af68f]
/lib/x86_64-linux-gnu/libisc-9.20.15-1~deb13u1-Debian.so(isc_assertion_failed+0x10)
[0x7648119af5d0]
/lib/x86_64-linux-gnu/libisc-9.20.15-1~deb13u1-Debian.so(isc_signal_start+0x4e)
[0x7648119d251e]
/lib/x86_64-linux-gnu/libisc-9.20.15-1~deb13u1-Debian.so(isc_loopmgr_nonblocking+0x1e)
[0x7648119c4a4e]
nslookup(+0x7591) [0x5adfb03a3591]
/lib/x86_64-linux-gnu/libisc-9.20.15-1~deb13u1-Debian.so(+0x61c94)
[0x7648119dbc94]
/lib/x86_64-linux-gnu/libuv.so.1(+0xb7e5) [0x7648110ca7e5]
/lib/x86_64-linux-gnu/libc.so.6(+0x92b7b) [0x76481150ab7b]
/lib/x86_64-linux-gnu/libc.so.6(+0x1107b8) [0x7648115887b8]
Aborted

After the second query, the > prompt does NOT appear until hitting enter.
Hitting enter a second time after this > prompt does appear results in
the crash.
Running a single lookup and exiting nslookup works normally.

dig @127.0.0.1 -p 5053 google.com AAAA +noall +answer +ttlunits
google.com.             1d      IN      HINFO   "AAAA queries have
been locally blocked by dnscrypt-proxy" "Set block_ipv6 to false to
disable that feature"