CVE-2026-5947
HighCVSS 7.5Exploitation Probability (EPSS)
Elevated risk70th percentile - higher than 70% of all known CVEs
Summary
A use-after-free vulnerability due to a race condition exists in BIND 9 versions 9.20.0 through 9.20.22, 9.21.0 through 9.21.21, and 9.20.9-S1 through 9.20.22-S1. During SIG(0) signature validation, if the 'recursive-clients' limit is reached and the message is discarded, validation may attempt to read the discarded message. Versions 9.18.28-9.18.49 and 9.18.28-S1-9.18.49-S1 are not affected.
Risk Assessment
An attacker can crash the BIND server, causing DNS service disruption and potential data leakage due to undefined behavior.
Recommendation
Upgrade BIND 9 to version 9.20.23 or later (or 9.21.22+), or switch to the unaffected 9.18.x branch.
Other vulnerabilities in BIND 9
See all- CVE-2026-77692High
An attacker can cause `named` to abort by sending a crafted DNS-over-HTTPS request with a cryptographically invalid SIG(0) record, and then closing the transport connection prematurely. This issue affects BIND 9 versions 9.20.0 through 9.20.27, 9.21.0 through 9.21.25, and 9.20.9-S1 through 9.20.27-S1.
- CVE-2025-13878High
Malformed BRID/HHIT records can cause `named` to terminate unexpectedly. This vulnerability affects specific versions of BIND 9.
- CVE-2000-0888Medium
named in BIND 8.2 through 8.2.2-P6 allows remote attackers to cause a denial of service by sending an SRV record to the server, aka the "srv bug."
- CVE-2000-0887Medium
named in BIND 8.2 through 8.2.2-P6 allows remote attackers to cause a denial of service by making a compressed zone transfer (ZXFR) request and performing a name service query on an authoritative record that is not cached, aka the "zxfr bug."
- CVE-1999-0024Medium
CVE-1999-0024 vulnerability involves a malicious attack on DNS cache via BIND, exploiting predictable query IDs.
- CVE-2026-97313High
A recursive BIND server that receives a query with recursion desired (RD=1) followed by a non-recursive query (RD=0) may exit with an assertion failure, resulting in a denial of service. To be vulnerable, the BIND server must allow recursive queries and have at least two RPZ zones configured: one with the default setting of "recursive-only yes", and the other with "recursive-only no". This issue affects BIND 9 versions 9.16.0 through 9.18.50, 9.20.0 through 9.20.29, 9.21.0 through 9.21.26, 9.11.3-S1 through 9.18.50-S1, and 9.20.9-S1 through 9.20.29-S1.
- CVE-2026-96888High
A BIND resolver that is configured with both a "redirect" zone and "qname-minimization strict" may abort with an assertion failure while processing the redirect. This issue affects BIND 9 versions 9.16.0 through 9.18.50, 9.20.0 through 9.20.29, 9.21.0 through 9.21.26, 9.16.8-S1 through 9.18.50-S1, and 9.20.9-S1 through 9.20.29-S1.
- CVE-2026-94300High
Replaying GSS-TSIG signed UDP messages can result in memory corruption in "named". An attacker who can capture a previously signed UDP message can replay it while the negotiated TSIG key is still valid, and by also sending crafted queries to a zone the attacker controls, may potentially achieve remote code execution.
- CVE-2026-19630High
In a BIND resolver, inbound DNS protocol messages with a particular structure will result in additional processing, with no limit imposed by BIND. A DNS message with a maliciously large number of such structures will cause BIND to consume disproportionate amounts of CPU time and memory during processing. This issue affects BIND 9 versions 9.11.0 through 9.18.50, 9.20.0 through 9.20.29, 9.21.0 through 9.21.26, 9.11.3-S1 through 9.18.50-S1, and 9.20.9-S1 through 9.20.29-S1.
- CVE-2026-80274High
If a BIND resolver sends a query for a DNSSEC-signed authoritative zone, and the authoritative server replies with a valid wildcard answer and signed NSEC3 proof, followed by an unsigned NSEC at the same owner name, it will trigger an unexpected program exit. This issue affects BIND 9 versions 9.11.0 through 9.18.50, 9.20.0 through 9.20.27, 9.21.0 through 9.21.25, 9.11.3-S1 through 9.18.50-S1, and 9.20.9-S1 through 9.20.27-S1.
Original NVD description (English source)
Undefined behavior may result due to a race condition leading to a use-after-free violation. If BIND receives an incoming DNS message signed with SIG(0), it begins work to validate that signature. If, during that validation, the "recursive-clients" limit is reached (as would occur during a query flood), and that same DNS message is discarded per the limit, there is a brief window of time while the SIG(0) validation may attempt to read the now-discarded DNS message. This issue affects BIND 9 versions 9.20.0 through 9.20.22, 9.21.0 through 9.21.21, and 9.20.9-S1 through 9.20.22-S1. BIND 9 versions 9.18.28 through 9.18.49 and 9.18.28-S1 through 9.18.49-S1 are NOT affected.
Vulnerability data from NVD (NIST) · CISA KEV · EPSS