CVE-2022-3924

named configured to answer from stale cache may terminate unexpectedly at recursive-clients soft quota

Description

This issue can affect BIND 9 resolvers with `stale-answer-enable yes;` that also make use of the option `stale-answer-client-timeout`, configured with a value greater than zero. If the resolver receives many queries that require recursion, there will be a corresponding increase in the number of clients that are waiting for recursion to complete. If there are sufficient clients already waiting when a new client query is received so that it is necessary to SERVFAIL the longest waiting client (see BIND 9 ARM `recursive-clients` limit and soft quota), then it is possible for a race to occur between providing a stale answer to this older client and sending an early timeout SERVFAIL, which may cause an assertion failure. This issue affects BIND 9 versions 9.16.12 through 9.16.36, 9.18.0 through 9.18.10, 9.19.0 through 9.19.8, and 9.16.12-S1 through 9.16.36-S1.

Remediation

Solution:

  • Upgrade to the patched release most closely related to your current version of BIND 9: 9.16.37, 9.18.11, 9.19.9, or 9.16.37-S1.

Workaround:

  • Disabling `stale-answer-client-timeout` entirely or setting the timeout value to zero prevents the problem. It is not possible to disable the limit on `recursive-clients`, though it could be set to a very high value in order to reduce the likelihood of encountering this scenario. However, this is not recommended as the limit on recursive clients is important for preventing exhaustion of server resources.

Category

7.5
CVSS
Severity: High
CVSS 3.1 •
EPSS 0.59%
Vendor Advisory isc.org
Affected: ISC BIND 9
Published at:
Updated at:

References

Link Tags
https://kb.isc.org/docs/cve-2022-3924 vendor advisory

Frequently Asked Questions

What is the severity of CVE-2022-3924?
CVE-2022-3924 has been scored as a high severity vulnerability.
How to fix CVE-2022-3924?
To fix CVE-2022-3924: Upgrade to the patched release most closely related to your current version of BIND 9: 9.16.37, 9.18.11, 9.19.9, or 9.16.37-S1.
Is CVE-2022-3924 being actively exploited in the wild?
As for now, there are no information to confirm that CVE-2022-3924 is being actively exploited. According to its EPSS score, there is a ~1% probability that this vulnerability will be exploited by malicious actors in the next 30 days.
What software or system is affected by CVE-2022-3924?
CVE-2022-3924 affects ISC BIND 9.
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