UBUNTU-CVE-2026-52682
[A crafted DNS packet can cause increased memory and CPU consumption]
Published Updated
PatchFirst · Latest vulnerabilities
dnsdist vulnerabilities
Vulnerabilities published for dnsdist in the last 30 days: 0. Listed in the KEV catalogue: 0.
Vulnerabilities: 32
h2o has HTTP/2 state amplification
h2o is an HTTP server with support for HTTP/1.x, HTTP/2 and HTTP/3. Prior to commit 9265bdd, there is an HTTP/2 state amplification issue that combines HPACK decompression amplification with Slowloris-style stream stalling. Amplified decoded header state can be retained by stalled HTTP/2 streams, and depending on the configuration, additional limits are needed to bound decoded header state and prevent attack. This issue has been fixed by commit 9265bdd.
Published Updatedh2o is vulnerable to musl libc stack overflow
h2o is an HTTP server with support for HTTP/1.x, HTTP/2 and HTTP/3. Prior to commit 6b5370d, h2o is vulnerable to a Denial of Service attack when calling alloca under certain conditions. When serving static files, h2o builds the file path on stack, by calling alloca. The maximum size of the memory allocated using alloca can be as huge as ~600KB, which exceeds the default pthread stack size used by musl libc (128KB). If the amount of memory allocated by alloca exceeds the stack size, the h2o server crashes with a segmentation fault, while it tries to touch the guard page. This issue has been fixed by commit 6b5370d.
Published Updatedh2o is vulnerable to heap overrun
h2o is an HTTP server with support for HTTP/1.x, HTTP/2 and HTTP/3. Prior to commit 8dc37cb, when h2o receives a ClientHello message over TLS or QUIC and it contains a zero-length SNI extension, the h2o server runs over the zero-length hostname while trying to copy the hostname, assuming that it is NULL-terminated. This is a potential denial-of-service attack vector in sense that it might trigger segmentation violation. This issue has been fixed by commit 8dc37cb.
Published Updatedh2o: musl libc stack overflow (QPACK)
h2o is an HTTP server with support for HTTP/1.x, HTTP/2 and HTTP/3. Prior to commit edd7a120bfc4af11ac0cbebce2a43cc1f93f9af1, when h2o processes a QPACK instruction sent from the peer over HTTP/3, lib/http3/qpack.c might allocate an on-stack buffer as large as approximately 800 KB by calling alloca, which exceeds the default pthread stack size used by musl libc and causes the h2o server to crash with a segmentation fault while touching the guard page. This issue is fixed in commit edd7a120bfc4af11ac0cbebce2a43cc1f93f9af1.
Published UpdatedEDNS options smuggling
An attacker can send a crafted EDNS OPT record that will be ignored by DNSdist’s filtering rules, but will be rewritten as a valid OPT record when EDNS Client Subnet is inserted, causing the backend to see the EDNS option(s) that DNSdist did not filter.
Published UpdatedDenial of service via crafted DoH3 queries
An attacker can send crafted DNS over HTTP/3 queries, triggering an exception that prevents some buffer from being freed right away. The buffer will be freed at the end of the QUIC connection, but on some setups it might be possible to open enough concurrent DoH3 streams to trigger an out-of-memory condition, resulting in a denial of service.
Published UpdatedOut-of-bounds read in SetMacAddrAction
An out-of-bounds read might happen when SetMacAddrAction is used, potentially resulting in uninitialized memory being sent over the network or a crash.
Published UpdatedDenial of service via IXFR queries
An attacker might be able to cause outgoing TCP connections to backend to be stuck until a timeout occurs instead of being released immediately, by sending IXFR queries. This could be used to cause a denial of service if there is a limit to the number of concurrent connections to this backend, or if the process runs out of file descriptors.
Published UpdatedDenial of service via DoH3 queries
An attacker might be able to delay the processing of DoH3 queries by sending DoH3 GET queries with an invalid DATA frame.
Published UpdatedPrometheus denial of service via crafted DNS queries
An attacker sending a large number of crafted DNS queries might be able to trigger a dynamic block being inserted with a value causing invalid output to be produced in the prometheus endpoint. The prometheus endpoint will then be rejected by the scraper until the dynamic block expires.
Published UpdatedInsufficient input validation of internal web server
An attacker can send a web request that causes unlimited memory allocation in the internal web server, leading to a denial of service. The internal web server is disabled by default.
Published UpdatedDenial of service via crafted DNSCrypt query
A client can trigger a divide by zero error leading to crash by sending a crafted DNSCrypt query.
Published UpdatedOutgoing DoH excessive memory allocation
A client can trigger excessive memory allocation by generating a lot of queries that are routed to an overloaded DoH backend, causing queries to accumulate into a buffer that will not be released until the end of the connection.
Published UpdatedDoQ/DoH3 excessive memory allocation
A client can trigger excessive memory allocation by generating a lot of errors responses over a single DoQ and DoH3 connection, as some resources were not properly released until the end of the connection.
Published UpdatedPRSD detection denial of service
PRSD detection denial of service
Published UpdatedTCP backend stream ID overflow
A client might theoretically be able to cause a mismatch between queries sent to a backend and the received responses by sending a flood of perfectly timed queries that are routed to a TCP-only or DNS over TLS backend.
Published UpdatedOut-of-bounds read in cache inspection via Lua
A cached crafted response can cause an out-of-bounds read if custom Lua code calls getDomainListByAddress() or getAddressListByDomain() on a packet cache.
Published UpdatedOut-of-bounds read in service discovery
A rogue backend can send a crafted SVCB response to a Discovery of Designated Resolvers request, when requested via either the autoUpgrade (Lua) option to newServer or auto_upgrade (YAML) settings. DDR upgrade is not enabled by default.
Published UpdatedOff-by-one access when processing crafted UDP responses
A rogue backend can send a crafted UDP response with a query ID off by one related to the maximum configured value, triggering an out-of-bounds write leading to a denial of service.
Published Updated
Check your server
Check your installed stack and versions against the current vulnerability feeds.