GHSA-hx4r-w6wj-j8fg: devalue: Residual sparse-array CPU amplification in uneval

October 1, 2026

uneval performs synchronous work proportional to a sparse array’s declared length. An application that passes attacker-influenced sparse values to uneval can suffer event-loop blocking. Since attacker-controlled creation of sparse arrays is so difficult, this vulnerability is very difficult to exploit.

References

github.com/advisories/GHSA-hx4r-w6wj-j8fg
github.com/sveltejs/devalue/commit/6861dbbb7e548849e48bce718e88747a298f7250
github.com/sveltejs/devalue/releases/tag/v5.9.3
github.com/sveltejs/devalue/security/advisories/GHSA-hx4r-w6wj-j8fg

Code Behaviors & Features

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