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  5. GHSA-5w5r-mf82-595p

GHSA-5w5r-mf82-595p: Cap'n Proto has Undefined Behavior in constant::Reader and StructSchema

January 28, 2026

The safe API functions constant::Reader::get and StructSchema::new rely on PointerReader::get_root_unchecked, which can cause undefined behavior (UB) by constructing arbitrary words or schemas.

References

  • github.com/advisories/GHSA-5w5r-mf82-595p
  • github.com/capnproto/capnproto-rust
  • github.com/capnproto/capnproto-rust/commit/7b981f4c75a975c80444cd38729bcdf12bf3eabf
  • github.com/capnproto/capnproto-rust/commit/e3aeec213e6d1b30a182bf61682a370f20d8a02c
  • github.com/capnproto/capnproto-rust/issues/605
  • rustsec.org/advisories/RUSTSEC-2025-0143.html

Code Behaviors & Features

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Affected versions

All versions before 0.24.0

Fixed versions

  • 0.24.0

Solution

Upgrade to version 0.24.0 or above.

Impact 9.8 CRITICAL

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

Learn more about CVSS

Weakness

  • CWE-758: Reliance on Undefined, Unspecified, or Implementation-Defined Behavior

Source file

cargo/capnp/GHSA-5w5r-mf82-595p.yml

Spotted a mistake? Edit the file on GitLab.

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