CVE-2026-50046— Possible heap use-after-free in an error path when a DoT forwarded query is jostled out

Possible heap use-after-free in an error path when a DoT forwarded query is jostled out

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.

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H

释放后使用

NLnet Labs Unbound 资源管理错误漏洞

NLnet Labs Unbound是荷兰NLnet Labs组织的域名系统解析服务器。 NLnet Labs Unbound 1.15.0版本至1.25.1版本存在资源管理错误漏洞，该漏洞源于释放后重用，当拥有结构中TCP流仍在握手时被移出网格，释放了引用字符串后的存储，从而读取释放后指针，导致守护进程崩溃，造成拒绝服务。

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