CVSS 4.0
8.7 highCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:NCVE-2026-123565
High (8.7) in sveltejs devalue. EPSS 0.3% estimated probability of exploitation activity in the next 30 days. Fixed in devalue 5.9.3.
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Sveltejs devalue before 5.9.3 contains a resource exhaustion vulnerability where repeated primitive strings cause quadratic expansion in the uneval function. Attackers can supply a small crafted payload that is parsed and then passed to uneval, producing a very large serialized string that exhausts memory or CPU.
Severity
CVSS 3.1
7.5 highCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H- EPSS
- 0.3% estimated probability of exploitation activity in the next 30 days; 28th percentile. Scored 2026-11-10. A forecast for this CVE across the internet, not for your own systems.
- CWE
- CWE-400 Uncontrolled Resource Consumption
- Published
- NVD analysis
- Awaiting analysis
- Record from
- the NVD, synced
Ask an AI about this CVE
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Explain CVE-2026-123565 for an engineer deciding whether to act. Use https://cve.bz/api/public/cves/CVE-2026-123565?via=ask-ai-copy and https://cve.bz/cve/CVE-2026-123565?via=ask-ai-copy as the source of truth: what is affected and which versions fix it, whether it is in CISA KEV, public exploits, and its EPSS (an internet-wide 30-day estimate of exploitation activity, not a forecast for my systems). If they give no fixed versions, use the CVE record https://cveawg.mitre.org/api/cve/CVE-2026-123565 or the vendor advisory, not third-party mirrors. Tell me how to check whether I am affected and how to verify a fix. Cite the sources and say where they are uncertain.Opens a third-party assistant; its answer is its own, not cve.bz's. The prompt holds only this CVE's id and public links.
Affected
Versions
From the CNA's record in the CVE List.
| Product | Affected |
|---|---|
| sveltejs devalue | before 5.9.3 |
Packages (OSV)
| Advisory | Ecosystem | Package | Affected | Fixed in |
|---|---|---|---|---|
| GHSA-mcm9-63f2-9j32 | npm | devalue | <5.9.3 | 5.9.3 |
Attack patterns (CAPEC)
- CAPEC-147 XML Ping of the Death Likelihood: Low · Severity: Medium
- CAPEC-227 Sustained Client Engagement
- CAPEC-492 Regular Expression Exponential Blowup
The attack patterns MITRE's CAPEC relates to this record's weaknesses, as MITRE names them. Credits.