Focus on capnproto vulnerabilities and metrics.
Last updated: 29 Mar 2026, 22:25 UTC
This page consolidates all known Common Vulnerabilities and Exposures (CVEs) associated with capnproto. We track both calendar-based metrics (using fixed periods) and rolling metrics (using gliding windows) to give you a comprehensive view of security trends and risk evolution. Use these insights to assess risk and plan your patching strategy.
For a broader perspective on cybersecurity threats, explore the comprehensive list of CVEs by vendor and product. Stay updated on critical vulnerabilities affecting major software and hardware providers.
Total capnproto CVEs: 9
Earliest CVE date: 17 Apr 2017, 21:59 UTC
Latest CVE date: 12 Mar 2026, 20:16 UTC
Latest CVE reference: CVE-2026-32240
30-day Count (Rolling): 2
365-day Count (Rolling): 2
Calendar-based Variation
Calendar-based Variation compares a fixed calendar period (e.g., this month versus the same month last year), while Rolling Growth Rate uses a continuous window (e.g., last 30 days versus the previous 30 days) to capture trends independent of calendar boundaries.
Month Variation (Calendar): 0%
Year Variation (Calendar): 0%
Month Growth Rate (30-day Rolling): 0.0%
Year Growth Rate (365-day Rolling): 0.0%
Average CVSS: 3.83
Max CVSS: 7.8
Critical CVEs (≥9): 0
| Range | Count |
|---|---|
| 0.0-3.9 | 4 |
| 4.0-6.9 | 2 |
| 7.0-8.9 | 3 |
| 9.0-10.0 | 0 |
These are the five CVEs with the highest CVSS scores for capnproto, sorted by severity first and recency.
Cap'n Proto is a data interchange format and capability-based RPC system. Prior to 1.4.0, when using Transfer-Encoding: chunked, if a chunk's size parsed to a value of 2^64 or larger, it would be truncated to a 64-bit integer. In theory, this bug could enable HTTP request/response smuggling. This vulnerability is fixed in 1.4.0.
Cap'n Proto is a data interchange format and capability-based RPC system. Prior to 1.4.0, a negative Content-Length value was converted to unsigned, treating it as an impossibly large length instead. In theory, this bug could enable HTTP request/response smuggling. This vulnerability is fixed in 1.4.0.
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 constant 4-byte string `{ 0x00, 0x00, 0xFF, 0xFF }`. Because this string is not controlled by the attacker, maintainers believe it is unlikely that remote code execution is possible. However, it cannot be ruled out. This functionality first appeared in Cap'n Proto 1.0. Previous versions are not affected. This issue is fixed in Cap'n Proto 1.0.1.1.
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 0.5.1.2, 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 0.4.1.1 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 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.
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.
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.