The remote Fedora 43 host has a package installed that is affected by multiple vulnerabilities as referenced in the FEDORA-2026-3170ee6a1c advisory.

    Update to 1.25.2 (rhbz#2506061)

    Security fixes:

    - Fix CVE-2026-14586, Assertion in libngtcp2 when under pressure in high concurrency DNS-over-QUIC     environments. Thanks to Kunta Chu, Kaihua Wang, and Jianjun Chen from Tsinghua University, for the report.
    - Fix CVE-2026-32665, Remote DNS-over-QUIC denial of service due to `quic-size` budget bypass. Thanks to     N0zoM1z0 (https://github.com/N0zoM1z0) for the report. In addition, thanks to Kunta Chu, Kaihua Wang, and     Jianjun Chen from Tsinghua University, for also reporting this issue. In addition, thanks to Qifan Zhang,     Palo Alto Networks, for also reporting this issue. In addition, thanks to Xuanchao Xie, for also reporting     this issue.
    - Fix CVE-2026-40691, Packet of death for DNSCrypt over TCP. Thanks to Qifan Zhang, Palo Alto Networks,     for the report. In addition, thanks to Trung Nguyen (@everping) of CyStack, for also reporting this issue.
    - Fix CVE-2026-41637, Degradation of resolution service from improperly accounted client-terminated DNS-     over-QUIC queries. Thanks to Qifan Zhang, Palo Alto Networks, for the report.
    - Fix CVE-2026-42955, Extra fix for CVE-2026-40622 to also clamp the TTL of A/AAAA records disallowing a     one-time 'ghost domain' delegation renewal via glue records. Thanks to Qifan Zhang, Palo Alto Networks,     for the report.
    - Fix CVE-2026-44621, Libunbound applications configured with 'unwanted-reply-threshold' could eventually     be abruptly terminated. Thanks to Qifan Zhang, Palo Alto Networks, for the report.
    - Fix CVE-2026-44687, Off-by-one error in 'harden-below-nxdomain' logic can shadow a stub/forward zone by     a legitimate parent's NXDOMAIN. Thanks to Qifan Zhang, Palo Alto Networks, for the report.
    - Fix CVE-2026-44690, Cross-zone wildcard cache poisoning via RRSIG.labels manipulation. Thanks to Qifan     Zhang, Palo Alto Networks, for the report.
    - Fix CVE-2026-46582, A wildcard replay, as another piece of data, triggers poisoning in the serve expired     reply path. Thanks to Qifan Zhang, Palo Alto Networks, for the report.
    - Fix CVE-2026-50045, 'max-global-quota' reset by DNSSEC validation restarts. Thanks to Kunjie Shang,     University of Science and Technology of China, for the report.
    - Fix CVE-2026-50046, Possible heap use-after-free in an error path when a DoT forwarded query is jostled     out. Thanks to Qifan Zhang, Palo Alto Networks, for the report.
    - Fix CVE-2026-50243, 'response-ip'/'rpz' can rewrite BOGUS answers instead of returning SERVFAIL. Thanks     to Qifan Zhang, Palo Alto Networks, for the report.
    - Fix CVE-2026-50248, BOGUS configured primary hostname accepted for XFR in auth/rpz zones. Thanks to     Qifan Zhang, Palo Alto Networks, for the report.
    - Fix CVE-2026-50251, Attacker supplied `0.0.0.0`/`::` glue triggers defensive full-cache flush. Thanks to     Qifan Zhang, Palo Alto Networks, for the report.
    - Fix CVE-2026-50252, Possible cache poisoning attack by mapping source port population per thread. Thanks     to Inbal Schussheim and Amit Klein, Hebrew University, for the report.
    - Fix CVE-2026-52863, Memory corruption could lead to crash and denial of service. Thanks to Qifan Zhang,     Palo Alto Networks, for the report.
    - Fix CVE-2026-54478, DNS Cookie bypass when combined with proxy-protocol use. Thanks to Qifan Zhang, Palo     Alto Networks, for the report.
    - Fix CVE-2026-55708, Privacy/configuration issue when adding local data in views through 'unbound-     control'. Thanks to Qifan Zhang, Palo Alto Networks, for the report.
    - Fix CVE-2026-55717, 'serve-expired-client-timeout' and 'response-ip' CNAME redirect could lead to a     crash. Thanks to Qifan Zhang, Palo Alto Networks, for the report. In addition, thanks to Xin Wang, Jiapeng     Li, and Jiajia Liu, Northwestern Polytechnical University, for also reporting this issue.
    - Fix CVE-2026-55973, 'dns-error-reporting: yes' leads to stack buffer overflow. Thanks to Qifan Zhang,     Palo Alto Networks, for the report.
    - Fix CVE-2026-55990, Packet of death for a DNSCrypt misconfigured Unbound. Thanks to Qifan Zhang, Palo     Alto Networks, for the report.
    - Fix CVE-2026-55991, Remote DNS-over-QUIC (DoQ) flow-control assertion failure in libngtcp2. Thanks to     Qifan Zhang, Palo Alto Networks, for the report. In addition, thanks to Xuanchao Xie, for also reporting     this issue.
    - Fix CVE-2026-56416, Possible heap buffer overflow when validator canonicalizes RDATA that contains     domain name. Thanks to Qifan Zhang, Palo Alto Networks, for the report.
    - Fix CVE-2026-56444, Degradation of resolution service when 'discard-timeout' and 'serve-expired-client-     timeout' are combined in unusual configuration. Thanks to Qifan Zhang, Palo Alto Networks, for the report.
    In addition, thanks to Xin Wang, Jiapeng Li, and Jiajia Liu, Northwestern Polytechnical University, for     also reporting this issue. In addition, thanks to Haruki Oyama (Waseda University), for also reporting     this issue.

    Source: https://nlnetlabs.nl/projects/unbound/download/#unbound-1-25-2



Tenable has extracted the preceding description block directly from the Fedora security advisory.

Note that Nessus has not tested for these issues but has instead relied only on the application's self-reported version number.

According to the versions of the unbound packages installed, the EulerOS Virtualization installation on the remote host is affected by the following vulnerabilities :

    In NLnet Labs Unbound 1.6.0 up to and including 1.25.1, the 'view_local_data' and 'view_local_datas'     commands of 'unbound-control' create a bare local zones tree for an already configured named view when the     view is configured with no local data to begin with. However, the creation through the control interface     omits adding the default-protected zones (e.g., RFC 1918 reverse, AS112 zones, .onion, .localhost). Once     the local zone tree exists without the defaults, every query for a default-protected name from a client     mapped to that view escapes to the public DNS via the iterator instead of being answered locally,     bypassing local policy expectations.(CVE-2026-55708)

    In NLnet Labs Unbound 1.4.22 up to and including 1.25.1, UDP source port is randomized and intended to     serve as a secret value that increases the entropy of DNS transactions. When resolver load balancing     policies depend on the source port while their outcome is revealed this secrecy is undermined. The     vulnerability arises when the load balancing policy is consistent with respect to the incoming source UDP     port and IP address while heavily depending on the incoming source UDP port as a randomization source.
    When the SO_REUSEPORT configuration option is enabled ('so-reuseport: yes') in Unbound (by default), it     meets these conditions, making it vulnerable for DNS cache poisoning attacks. Upon startup, Unbound     randomly partitions the available UDP source port space into disjoint subsets of (almost) equal size,     assigning each subset to a specific worker thread. When an incoming DNS query is received, the kernel's     SO_REUSEPORT load balancing mechanism deterministically assigns the query to a socket associated with a     particular thread. All outgoing DNS queries generated during the resolution of that request use source     ports selected exclusively from the port subset assigned to the corresponding thread. Since these port     subsets are disjoint across threads, the source port observed in a resolver's outgoing query to an     authoritative name server serves as a reliable indicator of the worker thread that processed the original     client query. A malicious actor can acquire the mapping between incoming UDP source ports (for a given     fixed source IP address) and Unbound worker threads and leverage it to conduct DNS cache poisoning attacks     by effectively lowering the random port population per thread.(CVE-2026-50252)

    In NLnet Labs Unbound 1.15.0 up to and including 1.25.1, the TLS server name used for DNS-over-TLS (DoT)     forwarded queries is tied to a struct's ('serviced_query') lifetime but also referenced by another struct     ('waiting_tcp'). When the owning struct is jostled out of the mesh while the DoT TCP stream is still     handshaking it frees the storage behind the referenced string and if the TLS stream then errors out, it     dereferences the freed pointer. The dereference is read-only and the practical impact is a daemon crash     resulting in denial of service. A malicious actor that knows a DoT forwarding/stub Unbound's configuration     could exploit the vulnerability by quering records in the appropriate zone while keeping Unbound uder     pressure so that the jostle logic kicks in. If answers for the vulnerable zone are slow, the likelihood of     jostling such queries is higher, although the timing of the jostle needs to be precise. Requirements for a     vulnerable Unbound is the existence of a stub/forward zone configured for DoT together with a configured     '#authname' suffix on the server identification. The connectivity to the server needs to exhibit a     transient failure at the correct time in order to kick off the vulnerable error path.(CVE-2026-50046)

    In NLnet Labs Unbound up to and including version 1.25.1, when the validator builds the canonical RDATA     form for an RRSIG-covered PX/RP/MINFO/SOA RRset, it computes the address of the second embedded domain     name as 'datstart + dname_valid(datstart, ...)' and passes it straight to 'query_dname_tolower()' without     checking that a second name is actually present in the RDATA. The wire-format parser accepts multi-dname     RRs whose RDATA ends after the first name, so an attacker who runs a DNSSEC-signed authoritative server     can deliver a record with an absent second domain name (e.g. SOA record) and cause 'query_dname_tolower()'     to walk label-by-label through stale bytes in the per-worker 'env-scratch_buffer', past the end of that     heap allocation if 'msg-buffer-size' has been lowered from the default. This leads to heap buffer overflow     and on a release build the outcome relies heavily on the contents of the buffer tail and the adjacent heap     chunk.(CVE-2026-56416)

    In NLnet Labs Unbound 1.16.2 up to and including 1.25.1, a similar vulnerability as with CVE-2026-40622 in     the 'ghost domain names' family of attacks was found in Unbound that could extend the ghost domain window     by up to one cached TTL configured value for A/AAAA glue records. Similar to other 'ghost domain names'     attacks, an adversary needs to control a (ghost) zone and be able to query a vulnerable Unbound. A single     client A/AAAA query can cause Unbound to overwrite the cached expired parent-side glue rrset and     essentially extend the ghost domain window by up to one cached TTL configured value ('cache-max-ttl'). In     configurations where 'harden-referral-path: yes' is used (non-default configuration), no client query is     required since Unbound implicitly performs that query. This is a variant of CVE-2026-40622 which only     addressed the NS query.(CVE-2026-42955)

    In NLnet Labs Unbound 1.6.2 up to and including 1.25.1, when Unbound is configured with the 'respip'     module in front of the validator together with a 'response-ip' redirect rule or an RPZ file with an RPZ-IP     trigger, the rewriting handler does not check the security status of the upstream answer and can instead     rewrite a BOGUS A/AAAA answer to point to an operator's configured IP. If the validator finds an expired     or otherwise invalid RRSIG on an answer whose A record falls within a 'response-ip'/RPZ configuration, the     answer is still rewritten and given a hard coded security level of INSECURE. This results in the client     receiving an INSECURE NOERROR reply rewritten by the operator's configured IP. A malicious actor can     exploit the possible poisonous effect by spoofing a BOGUS A/AAAA answer that falls inside the operator's     configured subnet rewrites. Such DNSSEC protected answers are then insecurely redirected to the operator's     configured target.(CVE-2026-50243)

    In NLnet Labs Unbound 1.7.0 up to and including 1.25.1, when the 'dnscrypt:' clause lists more 'dnscrypt-     provider-cert:' files than there are matching 'dnscrypt-secret-key:' files, Unbound fills only the matched     prefix and leaves the tail slots at the '0xdb' fill that libsodium's allocator writes into every     allocation. Unbound would then iterate over the number of cert files, not the actual slots, so it walks     into a slot with garbage data filled with '0xdb' bytes. Any unauthenticated client that sends one UDP     datagram of  68 bytes whose first 8 bytes are '0xdb' to 'dnscrypt-port' will use that garbage entry     which leads to a garbage dereference killing the server. This is a silent faulty configuration that goes     unnoticed until triggered with the right client query. Unbound needs to be compiled with DNSCrypt support     ('--enable-dnscrypt').(CVE-2026-55990)

    With NLnet Labs Unbound up to and including version 1.25.1, applications using libunbound and configured     with 'unwanted-reply-threshold', could eventually be abruptly terminated if the threshold is reached and     libunbound needs to call 'libworker_alloc_cleanup' since the function is absent from the function call     allow list. When an application using libunbound sets 'unwanted-reply-threshold' to any non-zero value and     the iterator queries an authoritative that replies with enough wrong-transaction-ID UDP datagrams to cross     the threshold, the 'libworker_alloc_cleanup' will eventually be called. Since the function is absent from     the function call allow list, this leads to a fatal exit of libunbound and eventual termination of the     embedding application.Unbound itself is not affected since its relevant function 'worker_alloc_cleanup' is     registed in the allow list and proceeds to perform the documented cache flush.(CVE-2026-44621)

    In NLnet Labs Unbound 1.13.2 up to and including 1.25.1, stub or forward zones where the name is below an     intermediate labed below a DNSSEC signed zone could be shadowed by the intermediate label's secure     NXDOMAIN answer from the parent. This is caused by an off-by-one error in 'harden-below-nxdomain' logic;
    enabled by default. It effectively bypasses the configuration and the configured stub/forward zone is     never contacted. 'harden-below-nxdomain' does an upward DNS cache walk together with a delegation point     guard that does not allow NXDOMAIN synthesis above stub/forward zones. The guard tests the domain name but     before stripping a label. This results in an iteration where the domain name equals the configured     stub/forward zone apex that passes the guard, strips one more label, and probes the cache at the apex's     immediate public parent. If that parent has a cached DNSSEC-secure NXDOMAIN, which it will for any private     namespace nested two or more labels under a signed public name, the walk returns it and the configured     stub/forward upstream is never contacted. This can only be triggered by the query for the intermediate     label (between the stub/forward apex and the DNSSEC parent zone).(CVE-2026-44687)

    In NLnet Labs Unbound 1.10.0 up to and including 1.25.1, when 'serve-expired: yes' is set together with a     'response-ip: net redirect' /'response-ip-data: net CNAME target' rule (or the RPZ 'rpz-     cname-override' equivalent), a remote client who controls any delegated domain can crash the daemon. The     serve-expired-client-timeout callback runs a two-pass loop to chase the respip-generated CNAME alias; on     the second pass it resets 'alias_rrset' but not 'partial_rep'. Later, this inconsistency leads to a NULL     pointer dereference and an eventual crash. A malicious actor can exploit the vulnerability by controlling     any zone that replies with an A/AAAA record that falls inside the configured response-ip/rpz subnet. By     delaying the answer when the previous record has expired, the vulnerable path of 'serve-expired-client-     timeout' is taken leading to denial of service via the server crash.(CVE-2026-55717)

    In NLnet Labs Unbound 1.6.0 up to and including 1.25.1, a replay of a wildcard rrset as another piece of     data, could be briefly considered DNSSEC secure based only on the RRSIG validation and stored into cache,     before later validation treats it as bogus based on NSEC validation. When the resolving thread puts secure     on the rrset, and another thread that is on the serve expired path then picks up the updated rrset     contents with the secure status for a reply, it can be used to change a specific record, next to a     wildcard that could be covered by the wildcard, into the wildcard. A malicious actor can exploit the     possible poisonous effect by having any DNSSEC-singed domain (irrelevant to the victim domain) and a CNAME     wrapper record that points to a record next to a wildcard (that could be covered by the wildcard). Then     quering Unbound for the wildcard sibling record would seed the secure message. A later (after expiry)     query for the CNAME wrapper would need to resolve the target sibling record. If the wildcard replay is     injected into the response, the wildcard rrset will update the expired sibling record with a secure status     before completing proper wildcard validation with NSEC records and eventually treating the CNAME wrapper     answer as bogus. The updated poisoned rrset is now secure and points to the wildcard. This vulnerability     is explicit for the serve expired path and needs injection of the signed wildcard rrset without the NSEC     accompanying rrset.(CVE-2026-46582)

    In NLnet Labs Unbound 1.7.0 up to and including 1.25.1, when an auth/rpz zone has a configured primary     hostname that resolves to BOGUS A/AAAA, it is still considered as a possible XFR endpoint. A malicious     actor that can spoof the hostname's A/AAAA record (no valid RRSIG required) becomes the zone's XFR primary     and can replaces the entire zone/the resolver's entire response policy.(CVE-2026-50248)

    In Unbound 1.9.0 up to and including 1.25.1, when a DNSCrypt query is received over TCP, the routine that     encrypts the reply in place fails to bound the reply length against the destination buffer size. The size     clamp that protects the UDP path is not applied on the TCP path, so a reply larger than 65504 bytes is     shifted forward by 48 bytes inside a buffer of capacity equal to 'msg-buffer-size', writing past the end     of the heap allocation. A single malicious encrypted query crashes the resolver and lead to denial of     service. This vulnerability needs Unbound to be compiled with DNSCrypt support ('--enable-dnscrypt') and     the 'dnscrypt:' clause to be configured and enabled for the listening interfaces.(CVE-2026-40691)

    In NLnet Labs Unbound 1.7.0 up to and including 1.25.1, insufficient validation of the RRSIG.Labels field     combined with premature cache writes during RFC 8198 aggressive NSEC processing leads to cache poisoning     that permits a malicious actor controlling a single delegated zone to poison arbitrary sibling zones under     NSEC-signed parent domains. A malicious actor with one registered domain under an NSEC-signed TLD can     serve malicious insecure DNS responses for unrelated sibling domains (sharing the same parent zone).
    Arbitrary delegations that do not exist under the parent domain and are covered by the parent's NSEC chain     can be brought into insecure existence by fraudulent wildcard DS records (less labels than expected,     unknown algorithm) from the malicious sibling domain. This allows the malicious actor to inject insecure     wildcard records for those delegations.(CVE-2026-44690)

    In NLnet Labs Unbound up to and including version 1.25.1, when 'unwanted-reply-threshold' is enabled (set     to any value greater than zero), glue records of 0.0.0.0/::0 can short-circuit Unbound, on systems that     can direct such traffic, by issuing DNS queries and receiving seemingly unwanted replies since the remote     IP does not match the original source IP of 0.0.0.0/::0. This behavior keeps on looping for the glue     records and pushing the counter to the configured 'unwanted-reply-threshold' that triggers a defensive     cache clear. A malicious actor who controls a delegation that returns in-bailiwick glue of 0.0.0.0/::0 can     drive the counter to the limit of 'unwanted-reply-threshold' to the threshold and trigger a cache clean of     the message and rrset caches; at will, indefinitely, without sending a single spoofed packet. The iterator     uses the 0.0.0.0/::0 glue, and a system that can route this (e.g., Linux kernel routes the datagram over     loopback), Unbound's own listener answers from 127.0.0.1. Because of the mismatch of 0.0.0.0 and     127.0.0.1, in this example, Unbound accounts the reply as an unwanted (probably spoofed) answer. The     counter resets to zero on every cache flush, so the attack loops forever.(CVE-2026-50251)

Tenable has extracted the preceding description block directly from the EulerOS Virtualization unbound security advisory.

Note that Nessus has not tested for these issues but has instead relied only on the application's self-reported version number.

ID	Name	Product	Family	Published	Updated	Severity
331344	Fedora 43 : unbound (2026-3170ee6a1c)	Nessus	Fedora Local Security Checks	7/31/2026	10/7/2026	high
377223	EulerOS Virtualization 2.15.0 : unbound (EulerOS-SA-2026-4857)	Nessus	Huawei Local Security Checks	11/7/2026	11/9/2026	high

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