Vulnerability in Tokio-Rs Bytes
CVE-2026-25541
Bytes is a utility library for working with bytes. From version 1.2.1 to before 1.11.1, Bytes is vulnerable to integer overflow in BytesMut::reserve. In the unique reclaim path of BytesMut::reserve, if the condition "v_capacity >= new_cap + offset" uses an unchecked addition. When new_cap + offset overflows usize in release builds, this condition may incorrectly pass, causing self.cap to be set to a value that exceeds the actual allocated capacity. Subsequent APIs such as spare_capacity_mut() then trust this corrupted cap value and may create out-of-bounds slices, leading to UB. This behavior is observable in release builds (integer overflow wraps), whereas debug builds panic due to overflow checks. This issue has been patched in version 1.11.1.
Published · last modified .
CVSS v3 metric
CVSS v3 base score 7.5 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H.
EPSS exploit prediction
EPSS: 0.006 (47.1th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 47th percentile — 47.1% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.006 · newest: 0.006 · change: +0.000
Affected products
- Tokio-Rs Bytes — versions >= 1.2.1, < 1.11.1
Weakness classification (CWE)
Public proof-of-concept exploits
References
- github.com/tokio-rs/bytes/security/advisories/GHSA-434x-w66g-qw3r (Exploit, Vendor Advisory)
- github.com/tokio-rs/bytes/commit/d0293b0e35838123c51ca5dfdf468ecafee4398f (Patch)
- github.com/tokio-rs/bytes/releases/tag/v1.11.1 (Product, Release Notes)
- rustsec.org/advisories/RUSTSEC-2026-0007.html (Exploit, Third Party Advisory)
Frequently asked questions
- What is CVE-2026-25541?
- CVE-2026-25541 is a high-severity vulnerability in Tokio-Rs Bytes, classified under Integer Overflow to Buffer Overflow. CVSS score: 7.5/10. Published 2026-02-04.
- How severe is CVE-2026-25541?
- High severity. CVSS v3 base score is 7.5 out of 10.
- Is CVE-2026-25541 known to be exploited?
- 2 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.