Cap'n Proto is a data interchange format and capability-based RPC system. In versions 1.0 and 1.0.1, when using the KJ HTTP library with WebSocket compression enabled, a buffer underrun can be caused by a remote peer. The underrun always writes a constant value that is not attacker-controlled, likely resulting in a crash, enabling a remote denial-of-service attack. Most Cap'n Proto and KJ users are unlikely to have this functionality enabled and so unlikely to be affected. Maintainers suspect only the Cloudflare Workers Runtime is affected. If KJ HTTP is used with WebSocket compression enabled, a malicious peer may be able to cause a buffer underrun on a heap-allocated buffer. KJ HTTP is an optional library bundled with Cap'n Proto, but is not directly used by Cap'n Proto. WebSocket compression is disabled by default. It must be enabled via a setting passed to the KJ HTTP library via `HttpClientSettings` or `HttpServerSettings`. The bytes written out-of-bounds are always a specific c…

Cap'n Proto is a data interchange format and remote procedure call (RPC) system. Cap'n Proro prior to versions 0.7.1, 0.8.1, 0.9.2, and 0.10.3, as well as versions of Cap'n Proto's Rust implementation prior to 0.13.7, 0.14.11, and 0.15.2 are vulnerable to out-of-bounds read due to logic error handling list-of-list. This issue may lead someone to remotely segfault a peer by sending it a malicious message, if the victim performs certain actions on a list-of-pointer type. Exfiltration of memory is possible if the victim performs additional certain actions on a list-of-pointer type. To be vulnerable, an application must perform a specific sequence of actions, described in the GitHub Security Advisory. The bug is present in inlined code, therefore the fix will require rebuilding dependent applications. Cap'n Proto has C++ fixes available in versions 0.7.1, 0.8.1, 0.9.2, and 0.10.3. The `capnp` Rust crate has fixes available in versions 0.13.7, 0.14.11, and 0.15.2.

Sandstorm Cap'n Proto before 0.4.1.1 and 0.5.x before 0.5.1.1 allows remote peers to cause a denial of service (CPU and possibly general resource consumption) via a list with a large number of elements.

Integer overflow in layout.c++ in Sandstorm Cap'n Proto before 0.4.1.1 and 0.5.x before 0.5.1.1 allows remote peers to cause a denial of service or possibly obtain sensitive information from memory via a crafted message, related to pointer validation.

Integer underflow in Sandstorm Cap'n Proto before 0.4.1.1 and 0.5.x before 0.5.1.1 might allow remote peers to cause a denial of service or possibly obtain sensitive information from memory or execute arbitrary code via a crafted message.

Sandstorm Cap'n Proto before 0.4.1.1 and 0.5.x before 0.5.1.2, when an application invokes the totalSize method on an object reader, allows remote peers to cause a denial of service (CPU consumption) via a crafted small message, which triggers a "tight" for loop. NOTE: this vulnerability exists because of an incomplete fix for CVE-2015-2312.

Sandstorm Cap'n Proto before 0.5.3.1 allows remote crashes related to a compiler optimization. A remote attacker can trigger a segfault in a 32-bit libcapnp application because Cap'n Proto relies on pointer arithmetic calculations that overflow. An example compiler with optimization that elides a bounds check in such calculations is Apple LLVM version 8.1.0 (clang-802.0.41). The attack vector is a crafted far pointer within a message.