CVE-2026-29795

Workarounds

Validate the byte length of string input before calling StringM::from_str, or construct StringM values via StringM::try_from(s.as_bytes().to_vec()) which correctly enforces the length constraint.

References

• Issue: https://github.com/stellar/rs-stellar-xdr/issues/499
• Fix: https://github.com/stellar/rs-stellar-xdr/pull/500

StringM::from_str does not validate that the input length is within the declared maximum (MAX). Calling StringM::<N>::from_str(s) where s is longer than N bytes succeeds and returns an Ok value instead of Err(Error::LengthExceedsMax), producing a StringM that violates its length invariant.

This affects any code that constructs StringM values from string input using FromStr (including str::parse), and relies on the type's maximum length constraint being enforced. An oversized StringM could propagate through serialization, validation, or other logic that assumes the invariant holds.

All published versions of the stellar-xdr crate up to and including v25.0.0 are affected.

The application allocates resources such as memory, threads, or file descriptors based on untrusted input without enforcing a cap. Typical impact: resource exhaustion leading to denial of service.

CVE-2026-29795 has a CVSS score of 4.0 (Medium). The vector is requires local access, no privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (25.0.1); upgrading removes the vulnerable code path.

Kodem intelligence

The fix is merged in #500. It replaces the direct Ok(Self(b)) construction with b.try_into(), which routes through TryFrom<Vec<u8>> and properly validates the length, matching the pattern already used by BytesM::from_str.

Users should upgrade to the first release containing this fix once published (the next release after v25.0.0).

1. What is CVE-2026-29795? CVE-2026-29795 is a medium-severity allocation of resources without limits or throttling vulnerability in stellar-xdr (rust), affecting versions <= 25.0.0. It is fixed in 25.0.1. The application allocates resources such as memory, threads, or file descriptors based on untrusted input without enforcing a cap.
2. How severe is CVE-2026-29795? CVE-2026-29795 has a CVSS score of 4.0 (Medium). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
3. Which versions of stellar-xdr are affected by CVE-2026-29795? stellar-xdr (rust) versions <= 25.0.0 is affected.
4. Is there a fix for CVE-2026-29795? Yes. CVE-2026-29795 is fixed in 25.0.1. Upgrade to this version or later.
5. Is CVE-2026-29795 exploitable, and should I be worried? Whether CVE-2026-29795 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
6. What actually determines whether CVE-2026-29795 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
7. How do I fix CVE-2026-29795? Upgrade stellar-xdr to 25.0.1 or later.