CVE-2026-56444— BIND9 解析服务降级漏洞
Possible ATT&CK Techniques 1AI
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I. CVE-2026-56444の基本情報
脆弱性情報
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脆弱性タイトル
Degradation of resolution service when 'discard-timeout' and 'serve-expired-client-timeout' are combined in unusual configuration
ソース: NVD (National Vulnerability Database)
脆弱性説明
In NLnet Labs Unbound 1.20.0 up to and including 1.25.1, when Unbound is configured with 'serve-expired: yes' and 'serve-expired-client-timeout > discard-timeout > 0' (contrary to the suggested values), the discard-timeout branch during the serve expired logic drops an aged client reply without performing the correct accounting for the number of reply addresses for the query. Other identical branches outside of serve expired perform the correct decrement. Since the counter is never decremented in such scenario, it can reach the maximum limit and new clients for duplicate in-flight queries are silently dropped resulting in degradation of resolution service. A malicious actor can exploit the vulnerability by querying the resolver for a client-controlled slow-on-demand authoritative zone that can drive the counter past the threshold. Shipped defaults for 'serve-expired-client-timeout: 1800' and 'discard-timeout: 1900' make the branch unreachable.
ソース: NVD (National Vulnerability Database)
CVSS情報
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
ソース: NVD (National Vulnerability Database)
脆弱性タイプ
对已超过有效生命周期的资源丧失索引
ソース: NVD (National Vulnerability Database)
影響を受ける製品
| ベンダー | プロダクト | 影響を受けるバージョン | CPE | 購読 |
|---|---|---|---|---|
| NLnet Labs | Unbound | 1.20.0 ~ 1.25.2 | - |
II. CVE-2026-56444の公開POC
| # | POC説明 | ソースリンク | Shenlongリンク |
|---|
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CVE-2026-56444 厂商安全公告 (1)
Same Patch Batch · NLnet Labs · 2026-07-22 · 24 CVEs total
| CVE-2026-55973 | 7.5 HIGH | 'dns-error-reporting: yes' leads to stack buffer overflow |
| CVE-2026-44690 | 7.5 HIGH | Cross-zone wildcard cache poisoning via RRSIG.labels manipulation |
| CVE-2026-32665 | 7.5 HIGH | Remote DNS-over-QUIC denial of service due to `quic-size` budget bypass |
| CVE-2026-40691 | 7.5 HIGH | Packet of death for DNSCrypt over TCP |
| CVE-2026-50248 | 6.5 MEDIUM | BOGUS configured primary hostname accepted for XFR in auth/rpz zones |
| CVE-2026-50046 | 5.9 MEDIUM | Possible heap use-after-free in an error path when a DoT forwarded query is jostled out |
| CVE-2026-55717 | 5.9 MEDIUM | 'serve-expired-client-timeout' and 'response-ip' CNAME redirect could lead to a crash |
| CVE-2026-55991 | 5.9 MEDIUM | Remote DNS-over-QUIC (DoQ) flow-control assertion failure in libngtcp2 |
| CVE-2026-55990 | 5.9 MEDIUM | Packet of death for a DNSCrypt misconfigured Unbound |
| CVE-2026-44621 | 5.9 MEDIUM | Libunbound applications configured with 'unwanted-reply-threshold' could eventually be abr |
| CVE-2026-52863 | 5.9 MEDIUM | Memory corruption could lead to crash and denial of service |
| CVE-2026-14586 | 5.9 MEDIUM | Assertion in libngtcp2 when under pressure in high concurrency DNS-over-QUIC environments |
| CVE-2026-50251 | 5.3 MEDIUM | Attacker supplied '0.0.0.0'/'::' glue triggers defensive full-cache flush |
| CVE-2026-50045 | 5.3 MEDIUM | 'max-global-quota' reset by DNSSEC validation restarts |
| CVE-2026-56416 | 4.8 MEDIUM | Possible heap buffer overflow when validator canonicalizes RDATA that contains domain name |
| CVE-2026-42955 | 3.7 LOW | Extra fix for CVE-2026-40622 to also clamp the TTL of A/AAAA records disallowing a one-tim |
| CVE-2026-54478 | 3.7 LOW | DNS Cookie bypass when combined with proxy-protocol use |
| CVE-2026-44687 | 3.7 LOW | Off-by-one error in 'harden-below-nxdomain' logic can shadow a stub/forward zone by a legi |
| CVE-2026-46582 | 3.7 LOW | A wildcard replay, as another piece of data, triggers poisoning in the serve expired reply |
| CVE-2026-41637 | 3.7 LOW | Degradation of resolution service from improperly accounted client-terminated DNS-over-QUI |
Showing 20 of 24 CVEs. View all on vendor page →
IV. 関連脆弱性
同じ製品: Unbound
- CVE-2026-56416
Possible heap buffer overflow when validator canonicalizes R - CVE-2026-55991
Remote DNS-over-QUIC (DoQ) flow-control assertion failure in - CVE-2026-55990
Packet of death for a DNSCrypt misconfigured Unbound - CVE-2026-55973
'dns-error-reporting: yes' leads to stack buffer overflow - CVE-2026-55717
'serve-expired-client-timeout' and 'response-ip' CNAME redir
同じベンダー: NLnet Labs
- CVE-2026-56416
Possible heap buffer overflow when validator canonicalizes R - CVE-2026-55991
Remote DNS-over-QUIC (DoQ) flow-control assertion failure in - CVE-2026-55990
Packet of death for a DNSCrypt misconfigured Unbound - CVE-2026-55973
'dns-error-reporting: yes' leads to stack buffer overflow - CVE-2026-55717
'serve-expired-client-timeout' and 'response-ip' CNAME redir
同じ弱点: CWE-772
- CVE-2026-41637
Degradation of resolution service from improperly accounted - CVE-2026-15713
Libsoup: soupcache: libsoup: http/2 frame window exhaustion - CVE-2026-54786
Wasmtime: Leak in WASIp1 `fd_renumber` implementation - CVE-2026-13351
net: Maliciously fragmented IPv6 packets can prevent receivi - CVE-2026-45287
OpenTelemetry-Go's Schema ParseFile leaks file descriptors o
V. CVE-2026-56444へのコメント
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