# CVE-2026-123562: Devalue 5.8.0 before 5.9.3 Denial of Service via stringifyAsync Unhandled Rejection

Status: published. Published: 2026-11-08. Updated: 2026-11-09.

devalue (sveltejs/devalue) 5.8.0 before 5.9.3 contains an unhandled promise rejection in stringifyAsync: when serializing multiple promises, a later promise rejecting before an earlier one settles leaves an internal rejection unhandled, even if the caller catches the returned promise. An attacker able to influence the timing or failure of serialized asynchronous values can terminate the Node.js process.

## Remediation

- fix: devalue (npm): OSV reports a fixed version 5.9.3. Check the advisory for supported release branches. (source: OSV GHSA-x5rw-q4pp-hg5g) — https://github.com/advisories/GHSA-x5rw-q4pp-hg5g

## Affected products and versions

- sveltejs / devalue (devalue): ≥ 5.8.0; < 5.9.3 (affected, semver); 5.9.3 (unaffected, semver). Source: CNA: VulnCheck
-  / devalue (devalue): ≥ 5.8.0; < 5.9.3 (affected, semver); OSV events: introduced 5.8.0; fixed 5.9.3. Source: OSV GHSA-x5rw-q4pp-hg5g

## Severity and prioritization

- CVSS 4.0: 8.7 (high); CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N; source: CNA: VulnCheck

- CVSS 3.1: 7.5 (high); CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H; source: CNA: VulnCheck

- CVSS 4.0: 8.7 (high); CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X; source: NVD: disclosure@vulncheck.com

- CVSS 3.1: 7.5 (high); CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H; source: NVD: disclosure@vulncheck.com

- CISA KEV: No listing in collected sources

- EPSS: 0.34% as of 2026-11-08; percentile 28.07%

- SSVC: exploitation none; automatable yes; technical impact partial; source ADP: CISA-ADP

- Weaknesses: CWE-248

## Exploit evidence

No exploit evidence in collected sources. This is not proof of no exploitation.

## References

- https://github.com/sveltejs/devalue/security/advisories/GHSA-x5rw-q4pp-hg5g (CNA: VulnCheck; vendor-advisory)

- https://www.vulncheck.com/advisories/devalue-5.8.0-before-5.9.3-denial-of-service-via-stringifyasync-unhandled-rejection (CNA: VulnCheck; third-party-advisory)

- https://github.com/sveltejs/devalue/security/advisories/GHSA-x5rw-q4pp-hg5g (disclosure@vulncheck.com)

- https://www.vulncheck.com/advisories/devalue-5.8.0-before-5.9.3-denial-of-service-via-stringifyasync-unhandled-rejection (disclosure@vulncheck.com)

- https://github.com/advisories/GHSA-x5rw-q4pp-hg5g (OSV / GitHub Security Advisories; advisory)

- https://osv.dev/vulnerability/GHSA-x5rw-q4pp-hg5g (OSV / GitHub Security Advisories; osv)

## Provenance

- CNA: VulnCheck: https://www.cve.org/CVERecord?id=CVE-2026-123562; retrieved 2026-11-09; source updated 2026-11-09

- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-123562; retrieved 2026-11-08; source updated 2026-11-08

- OSV / GitHub Security Advisories: https://osv.dev/vulnerability/GHSA-x5rw-q4pp-hg5g; retrieved 2026-11-09; source updated 2026-11-08

- FIRST EPSS: https://api.first.org/data/v1/epss?cve=CVE-2026-123562; retrieved 2026-11-09; source updated Not reported

Revision: c8efea28ddfe3d7462dcf66bb617a52a17685805ca0dcc653138930c2cc37fdd

Canonical: https://y2.dev/cve/CVE-2026-123562

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