unbounded-spsc: Sender::send pointer-as-value transmute causes OOB read and fake-Arc drop under TX/RX race

published 2026-05-29 5 mo ago modified 2026-10-26 14 d ago also GHSA-6m57-8r3p-pqx6 , EUVD-2026-36469

cvss: 5.8; version 3.1, CNA
cisa kev: Not listed; not in CISA's catalog
epss: 0.1%; EPSS 0.1% chance of exploitation in 30 days, percentile 2%
public exploits: 0; none known

unbounded_spsc is an "unbounded" extension of bounded_spsc_queue. In versions 0.2.0 and prior, sender::send pointer-as-value transmute causes OOB read and fake-Arc drop under TX/RX race. At time of publication, there are no publicly available patches.

CISA SSVC

Exploitation: Proof of concept is public
Automatable: no
Technical impact: partial
Assessed: 4 mo ago (2026-06-12)

Exploit prediction

0.13% chance of exploitation in the next 30 days, higher than 2% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

github.com https://github.com/spearman/unbounded-spsc/security/advisories/GHSA-6m57-8r3p-pqx6 referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by	version	score	vector
CNA	3.1	5.8	CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:H
NVD	3.1	5.8	CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:H
GitHub	3.1	5.8	CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:H

Affected packages

ecosystem	package	affected	fixed in
crates.io	unbounded-spsc	<=0.2.0	no fix listed

Affected products

spearman unbounded-spsc

Classification

Weakness

CWE-125 Out-of-bounds Read
CWE-415 Double Free
CWE-704 Incorrect Type Conversion or Cast
CWE-787 Out-of-bounds Write

References

github.com /spearman/unbounded-spsc/security/advisories/GHSA-6m57-8r3p-pqx6
exploit, web, vendor-advisory
nvd.nist.gov /vuln/detail/CVE-2026-46690
advisory
github.com /spearman/unbounded-spsc
package

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

Summary