Quick answers
- Is CVE-2026-123569 exploited in the wild?
- No. Junglewise Threat Intelligence has no report of CVE-2026-123569 being exploited in the wild.
- How severe is CVE-2026-123569?
- High severity, with a CVSS score of 7.5, published 8 November 2026.
- Which products and versions are affected?
- Sveltejs Devalue before 5.6.3.
- Is there a fix for CVE-2026-123569?
- Yes: fixed in 5.6.3. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
- How is CVE-2026-123569 attacked?
- It is attacked over the network.
- Am I affected by CVE-2026-123569?
- Check whether you run Sveltejs Devalue at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.
How to fix
- Fixed in: 5.6.3
Technical details
A resource exhaustion vulnerability in the devalue package's uneval and stringify functions fails to handle sparse arrays efficiently, leading to CPU and memory amplification. The attack requires an attacker to create a sparse array on the server-side and trigger its serialization, which is difficult in practice since mainstream wire formats do not support sparse arrays. A fix is available in version 5.6.3.
Affected products
- sveltejs devalue before 5.6.3
Timeline
- 2026-02-18: disclosed
- 2026-11-08: advisory