In Vinyl Cache before 9.0,2, workspace buffer overflow vulnerability was found in the .upper() and .lower() string type methods of VCL. This can be used as a remote denial of service (DoS) vector to make the child process segfault or assert, and then restart. Effectively exploiting this vulnerability requires prior knowledge about the VCL in use and the ability to craft a request that contains a string that is long enough to fill the remaining workspace at the call site while staying under the different request size limits (http_req_size, http_req_hdr_len, etc.).
In Vinyl Cache before 9.0.1 and Varnish Cache before 9.0.3, a deficiency in HTTP/2 request parsing can be exploited to launch a backend request desync
attack (request smuggling), which in turn can be used for cache poisoning,
authentication bypass, or possibly even information disclosure and manipulation. The attack vector only exists if HTTP/2 support is enabled by setting the
feature parameter to contain +http2. HTTP/2 support is disabled by
default.
Varnish Cache 9 before 9.0.1 allows a "workspace overflow" denial of service (daemon panic) after timeout_linger. A malicious client could send an HTTP/1 request, wait long enough until the session releases its worker thread (timeout_linger) and resume traffic before the session is closed (timeout_idle) sending more than one request at once to trigger a pipelining operation between requests. This vulnerability affecting Varnish Cache 9.0.0 emerged from a port of the Varnish Enterprise non-blocking architecture for HTTP/2. New code was needed to adapt to a more recent workspace API that formalizes the pipelining operation. In addition to the w
Varnish Enterprise before 6.0.16r12 allows a "workspace overflow" denial of service (daemon panic) for shared VCL. The headerplus.write_req0() function from vmod_headerplus updates the underlying req0, which is normally the original read-only request from which req is derived (readable and writable from VCL). This is useful in the active VCL, after amending req, to prepare a refined req0 before switching to a different VCL with the return (vcl(<label>)) action. This is for example how the Varnish Controller operates shared VCL deployments. If the amended req contained too many header fields for req0, this would have resulted in a workspace ov
Varnish Cache 9 before 9.0.1 and Varnish Enterprise before 6.0.16r11 allows a "workspace overflow" denial of service (daemon panic) for certain amounts of prefetched data. The setup of an HTTP/2 session starts with a speculative HTTP/1 transport, and upon upgrading to h2 the HTTP/1 request is repurposed as stream zero. During the upgrade, a buffer allocation is made to reserve space to send frames to the client. This allocation would split the original workspace, and depending on the amount of prefetched data, the next fetch could perform a pipelining operation that would run out of workspace.
Media · CVSS 5.4EPSS 0,21%Sin corrección publicada
CVE-2026-34475
Varnish Cache before 8.0.1 and Varnish Enterprise before 6.0.16r12, in certain unchecked req.url scenarios, mishandle URLs with a path of / for HTTP/1.1, potentially leading to cache poisoning or authentication bypass.
A mismatch caused by client-triggered server-sent stream resets between HTTP/2 specifications and the internal architectures of some HTTP/2 implementations may result in excessive server resource consumption leading to denial-of-service (DoS). By opening streams and then rapidly triggering the server to reset them—using malformed frames or flow control errors—an attacker can exploit incorrect stream accounting. Streams reset by the server are considered closed at the protocol level, even though backend processing continues. This allows a client to cause the server to handle an unbounded number of concurrent streams on a single connection. Th
Media · CVSS 5.4EPSS 0,37%Sin corrección publicada
CVE-2025-47905
Varnish Cache before 7.6.3 and 7.7 before 7.7.1, and Varnish Enterprise before 6.0.13r14, allow client-side desync via HTTP/1 requests, because the product incorrectly permits CRLF to be skipped to delimit chunk boundaries.
In Varnish Cache before 6.6.2 and 7.x before 7.0.2, Varnish Cache 6.0 LTS before 6.0.10, and and Varnish Enterprise (Cache Plus) 4.1.x before 4.1.11r6 and 6.0.x before 6.0.9r4, request smuggling can occur for HTTP/1 connections.
Varnish 3.x before 3.0.7, when used in certain stacked installations, allows remote attackers to inject arbitrary HTTP headers and conduct HTTP response splitting attacks via a header line terminated by a \r (carriage return) character in conjunction with multiple Content-Length headers in an HTTP request.
Crítica · CVSS 9.8EPSS 13%Código de explotación públicoSin corrección publicada
CVE-2009-4488
Varnish 2.0.6 writes data to a log file without sanitizing non-printable characters, which might allow remote attackers to modify a window's title, or possibly execute arbitrary commands or overwrite files, via an HTTP request containing an escape sequence for a terminal emulator. NOTE: the vendor disputes the significance of this report, stating that "This is not a security problem in Varnish or any other piece of software which writes a logfile. The real problem is the mistaken belief that you can cat(1) a random logfile to your terminal safely.