CVE-2023-2911

Exceeding the recursive-clients quota may cause named to terminate unexpectedly when stale-answer-client-timeout is set to 0

Description

If the `recursive-clients` quota is reached on a BIND 9 resolver configured with both `stale-answer-enable yes;` and `stale-answer-client-timeout 0;`, a sequence of serve-stale-related lookups could cause `named` to loop and terminate unexpectedly due to a stack overflow. This issue affects BIND 9 versions 9.16.33 through 9.16.41, 9.18.7 through 9.18.15, 9.16.33-S1 through 9.16.41-S1, and 9.18.11-S1 through 9.18.15-S1.

Remediation

Solution:

  • Upgrade to the patched release most closely related to your current version of BIND 9: 9.16.42, 9.18.16, 9.16.42-S1, or 9.18.16-S1.

Workaround:

  • Setting `stale-answer-client-timeout` to `off` or to a non-zero value prevents the issue. Users of versions 9.18.10, 9.16.36, 9.16.36-S1 or older who are unable to upgrade should set `stale-answer-client-timeout` to `off`; using a non-zero value with these older versions leaves `named` vulnerable to CVE-2022-3924. Although it is possible to set the `recursive-clients` limit to a high number to reduce the likelihood of this scenario, this is not recommended; the limit on `recursive-clients` is important for preventing exhaustion of server resources. The limit cannot be disabled entirely.

Category

7.5
CVSS
Severity: High
CVSS 3.1 •
EPSS 0.17%
Vendor Advisory isc.org
Affected: ISC BIND 9
Published at:
Updated at:

References

Link Tags
https://kb.isc.org/docs/cve-2023-2911 vendor advisory
http://www.openwall.com/lists/oss-security/2023/06/21/6 patch mailing list third party advisory
https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/U3K6AJK7RRSR53HRF5GGKPA6PDUDWOD2/ third party advisory mailing list
https://www.debian.org/security/2023/dsa-5439 third party advisory
https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/SEFCEVCTYEMKTWA7V7EYPI5YQQ4JWDLI/ third party advisory mailing list
https://security.netapp.com/advisory/ntap-20230703-0010/ third party advisory

Frequently Asked Questions

What is the severity of CVE-2023-2911?
CVE-2023-2911 has been scored as a high severity vulnerability.
How to fix CVE-2023-2911?
To fix CVE-2023-2911: Upgrade to the patched release most closely related to your current version of BIND 9: 9.16.42, 9.18.16, 9.16.42-S1, or 9.18.16-S1.
Is CVE-2023-2911 being actively exploited in the wild?
As for now, there are no information to confirm that CVE-2023-2911 is being actively exploited. According to its EPSS score, there is a ~0% probability that this vulnerability will be exploited by malicious actors in the next 30 days.
What software or system is affected by CVE-2023-2911?
CVE-2023-2911 affects ISC BIND 9.
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