CVE-2020-35865
os_str_bytes relies on undefined behavior of `char::from_u32_unchecked`
An issue was discovered in the os_str_bytes crate before 2.0.0 for Rust. It has false expectations about char::from_u32_unchecked behavior.
Attack profile
How easy it is to exploit
- Attack vector
- Network
- Complexity
- Low
- Privileges needed
- None
- User interaction
- None
What an attacker can affect
- Confidentiality
- None
- Integrity
- None
- Availability
- High
Exploit likelihood
What each source reports
NVD Score used
An issue was discovered in the os_str_bytes crate before 2.0.0 for Rust. It has false expectations about char::from_u32_unchecked behavior.
- Record
CVE-2020-35865- CVSS 3.1
- 7.5 High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H - CVSS 2.0
- 5.0 Medium
AV:N/AC:L/Au:N/C:N/I:N/A:P - Updated
- 2026-11-02
CVE List No score
An issue was discovered in the os_str_bytes crate before 2.0.0 for Rust. It has false expectations about char::from_u32_unchecked behavior.
- Record
CVE-2020-35865- Updated
- 2026-11-02
EUVDEUVD-2021-1837 No score
An issue was discovered in the os_str_bytes crate before 2.0.0 for Rust. It has false expectations about char::from_u32_unchecked behavior.
- Record
EUVD-2021-1837- Updated
- 2026-11-03
GitHub AdvisoriesGHSA-q948-x8rf-888m
os_str_bytes relies on undefined behavior of `char::from_u32_unchecked`
The Windows implementation of this crate relied on the behavior of std::char::from_u32_unchecked when its safety clause is violated. Even though this worked with Rust versions up to 1.42 (at least), that behavior could change with any new Rust version, possibly leading a security issue.
The flaw was corrected in version 2.0.0.
- Record
GHSA-q948-x8rf-888m- CVSS 3.1
- 7.5 High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H - Weakness
- CWE-704
- Updated
- 2026-11-02
OSV
An issue was discovered in the os_str_bytes crate before 2.0.0 for Rust. It has false expectations about char::from_u32_unchecked behavior.
- Record
CVE-2020-35865- CVSS 3.1
- 7.5 High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H - Updated
- 2026-11-02
OSVGHSA-q948-x8rf-888m
os_str_bytes relies on undefined behavior of `char::from_u32_unchecked`
The Windows implementation of this crate relied on the behavior of std::char::from_u32_unchecked when its safety clause is violated. Even though this worked with Rust versions up to 1.42 (at least), that behavior could change with any new Rust version, possibly leading a security issue.
The flaw was corrected in version 2.0.0.
- Record
GHSA-q948-x8rf-888m- CVSS 3.1
- 7.5 High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H - Weakness
- CWE-704
- Updated
- 2026-11-02
OSVRUSTSEC-2020-0012
Relies on undefined behavior of `char::from_u32_unchecked`
The Windows implementation of this crate relied on the behavior of
std::char::from_u32_unchecked when its safety clause is violated.
Even though this worked with Rust versions up to 1.42 (at least),
that behavior could change with any new Rust version, possibly leading
a security issue.
The flaw was corrected in version 2.0.0.
- Record
RUSTSEC-2020-0012- CVSS 3.1
- 7.5 High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H - Updated
- 2026-11-02
Affected products
Affected packages
| Package | Affected | Fixed |
|---|---|---|
os_str_bytescrates.io |
before 2.0.0 | 2.0.0 |
os_str_bytescrates.io |
0.0.0-0 up to 2.0.0 | 2.0.0 |
History
| Recorded | Changed | Sources |
|---|---|---|
| facts | ||
| aliases | EUVD | |
| first indexed | CVE List, GitHub Advisories, NVD, OSV |
Dates are when Every CVE recorded each change. Upstream dates may differ.
In short
CVE-2020-35865 is a high vulnerability (CVSS 7.5) in Os Str Bytes Project Str Bytes, published April 24, 2020. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 1.35%, the 71st percentile. Fixed in os_str_bytes 2.0.0.