Distribution advisory
This page covers CVE-2026-42256 as tracked by Ubuntu, for the package jruby. The fix is available in version 3.3.8-2ubuntu3.1; earlier versions remain affected.
How this vulnerability can be exploited
This issue can be reached over the network, attack complexity is low, an attacker needs no privileges on the target. A user must be tricked into taking some action. The scope is unchanged, so the impact stays within the vulnerable component. Rated impact: confidentiality none, integrity none, availability high.
CVSS metrics in full
The score comes from this vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H
- Attack vector: Network — reachable from anywhere that can route to the service.
- Attack complexity: Low — the attack works reliably, with no preparation.
- Privileges required: None — an unauthenticated stranger can try it.
- User interaction: Required — someone has to click, open or visit something.
- Scope: Unchanged — the damage stays inside the vulnerable component.
- Confidentiality impact: None.
- Integrity impact: None.
- Availability impact: High — total loss, or loss the attacker controls.
Weakness class
UBUNTU-CVE-2026-42256 is classified as CWE-1322: Use of Blocking Code in Single-threaded, Non-blocking Context. The product uses a non-blocking model that relies on a single threaded process for features such as scalability, but it contains code that can block when it is invoked.
Affected software
UBUNTU-CVE-2026-42256 is recorded against 2 packages.
- jruby
- ruby3.3 (fixed in 3.3.8-2ubuntu3.1)
Timeline and source
Published on 9 May 2026 and last revised on 6 July 2026. No public exploit is currently recorded for this entry. Record sourced from OSV.
References
ubuntu.com (Report)
www.cve.org (Report)
github.com (Report)
github.com (Report)
github.com (Report)
github.com (Report)
github.com (Report)
github.com (Report)
github.com (Report)
ubuntu.com (Advisory)
Other advisories for this package
jruby has other advisories on record. If you are patching this one, these are worth checking on the same host:
Same weakness in other software
These advisories are the same class of weakness (CWE-1322: Use of Blocking Code in Single-threaded, Non-blocking Context) in other software:
