Bug 820563 – <net-dns/bind-9.16.22: Lame cache can be abused to severely degrade resolver performance (CVE-2021-25219)

• Status: RESOLVED FIXED
• Product: Gentoo Security

[Description Sam James 2021-10-28 01:39:25 UTC]

```
Exploitation of broken authoritative servers using a flaw in response processing can cause degradation in BIND resolver performance. The way the lame cache is currently designed makes it possible for its internal data structures to grow almost infinitely, which may cause significant delays in client query processing.

The purpose of a resolver's lame cache is to ensure that if an authoritative server responds to a resolver's query in a specific broken way, subsequent client queries for the same <QNAME, QTYPE> tuple do not trigger further queries to the same server for a configurable amount of time. The lame cache is enabled by setting the lame-ttl option in named.conf to a value greater than 0. That option is set to lame-ttl 600; in the default configuration, which means the lame cache is enabled by default.

Impact:

Authoritative-only BIND 9 servers are NOT vulnerable to this flaw.

A successful attack exploiting this flaw causes a named resolver to spend most of its CPU time on managing and checking the lame cache. This results in client queries being responded to with large delays, and increased likelihood of DNS timeouts on client hosts.
```

[Comment 1 Larry the Git Cow 2021-10-28 02:01:56 UTC]

The bug has been referenced in the following commit(s):

https://gitweb.gentoo.org/repo/gentoo.git/commit/?id=4ef29a2c6d73b51b46325a4070a79d4c4daaa969

commit 4ef29a2c6d73b51b46325a4070a79d4c4daaa969
Author:     Sam James <[e-mail]>
AuthorDate: 2021-10-28 02:01:07 +0000
Commit:     Sam James <[e-mail]>
CommitDate: 2021-10-28 02:01:39 +0000

    net-dns/bind-tools: add 9.16.22 (security bump)
    
    Bug: https://bugs.gentoo.org/820563
    Signed-off-by: Sam James <[e-mail]>

 net-dns/bind-tools/Manifest                  |   1 +
 net-dns/bind-tools/bind-tools-9.16.22.ebuild | 148 +++++++++++++++++++++++++++
 2 files changed, 149 insertions(+)

https://gitweb.gentoo.org/repo/gentoo.git/commit/?id=7916382847660dca423c35c199bbab7f2b5576c4

commit 7916382847660dca423c35c199bbab7f2b5576c4
Author:     Sam James <[e-mail]>
AuthorDate: 2021-10-28 01:58:50 +0000
Commit:     Sam James <[e-mail]>
CommitDate: 2021-10-28 02:01:38 +0000

    net-dns/bind: add 9.16.22 (security bump)
    
    Bug: https://bugs.gentoo.org/820563
    Signed-off-by: Sam James <[e-mail]>

 net-dns/bind/Manifest            |   1 +
 net-dns/bind/bind-9.16.22.ebuild | 373 +++++++++++++++++++++++++++++++++++++++
 2 files changed, 374 insertions(+)

[Comment 2 John Helmert III 2021-11-10 12:40:46 UTC]

Please cleanup.

[Comment 3 John Helmert III 2022-10-22 01:33:45 UTC]

GLSA request filed.

[Comment 4 Larry the Git Cow 2022-10-31 01:21:32 UTC]

The bug has been referenced in the following commit(s):

https://gitweb.gentoo.org/repo/gentoo.git/commit/?id=8bdc575dae63f16d44b926f18271d15d3173fc5f

commit 8bdc575dae63f16d44b926f18271d15d3173fc5f
Author:     John Helmert III <[e-mail]>
AuthorDate: 2022-10-31 01:19:33 +0000
Commit:     John Helmert III <[e-mail]>
CommitDate: 2022-10-31 01:20:11 +0000

    net-dns/bind: security cleanup
    
    Bug: https://bugs.gentoo.org/820563
    Bug: https://bugs.gentoo.org/835439
    Bug: https://bugs.gentoo.org/872206
    Acked-by: Patrick McLean <[e-mail]>
    Signed-off-by: John Helmert III <[e-mail]>

 net-dns/bind/Manifest                              |   5 -
 net-dns/bind/bind-9.16.27-r1.ebuild                | 375 --------------------
 net-dns/bind/bind-9.16.29-r1.ebuild                | 376 --------------------
 net-dns/bind/bind-9.16.29.ebuild                   | 375 --------------------
 net-dns/bind/bind-9.16.30.ebuild                   | 381 --------------------
 net-dns/bind/bind-9.16.31.ebuild                   | 382 ---------------------
 net-dns/bind/bind-9.16.32.ebuild                   | 382 ---------------------
 .../bind/files/bind-9.16.29-fortify-source-3.patch |  35 --
 8 files changed, 2311 deletions(-)

[Comment 5 Larry the Git Cow 2022-10-31 01:42:17 UTC]

The bug has been referenced in the following commit(s):

https://gitweb.gentoo.org/data/glsa.git/commit/?id=3ff54f9ebabdb1f657769518402d72abd34fbdcb

commit 3ff54f9ebabdb1f657769518402d72abd34fbdcb
Author:     GLSAMaker <[e-mail]>
AuthorDate: 2022-10-31 01:18:02 +0000
Commit:     John Helmert III <[e-mail]>
CommitDate: 2022-10-31 01:40:16 +0000

    [ GLSA 202210-25 ] ISC BIND: Multiple Vulnerabilities
    
    Bug: https://bugs.gentoo.org/820563
    Bug: https://bugs.gentoo.org/835439
    Bug: https://bugs.gentoo.org/872206
    Signed-off-by: GLSAMaker <[e-mail]>
    Signed-off-by: John Helmert III <[e-mail]>

 glsa-202210-25.xml | 63 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 63 insertions(+)

[Comment 6 John Helmert III 2022-10-31 02:22:12 UTC]

GLSA released, all done!