TI-2024-21538 Aliases CVE-2024-32657

Hydra has persistent XSS vulnerability serving HTML build outputs

LOW 31CWE-79Published 2024-04-22 · Updated 2024-08-02

Key facts

Attack vector: Network
Privileges required: Low
User interaction: Required
Attack complexity: Low
Impact type: Cross-site scripting
Confidentiality · integrity · availability: Low · Low · None
Fix status: Fixed

Attack profile from CVSS 3.1 · NVD. Fix status from CNA. Impact type from CWE-79.

Summary

Hydra is a Continuous Integration service for Nix based projects. Attackers can execute arbitrary code in the browser context of Hydra and execute authenticated HTTP requests. The abused feature allows Nix builds to specify files that Hydra serves to clients. One use of this functionality is serving NixOS `.iso` files. The issue is only with html files served by Hydra. The issue has been patched on https://hydra.nixos.org around 2024-04-21 14:30 UTC. The nixpkgs package were fixed in unstable and 23.11. Users with custom Hydra packages can apply the fix commit to their local installations. The vulnerability is only triggered when opening HTML build artifacts, so not opening them until the vulnerability is fixed works around the issue.

Why it matters now

Exploitation None reported CISA SSVC · not in CISA KEV

EPSS 0.00467 40th percentileScored 2026-11-07

Fix Fixed hydra (NixOS): 23.11

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation: None
Automatable: Yes
Technical impact: Partial

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

Vendor	Product	Affected versions	Fixed in	Status	Source
NixOS	hydra	< b72528be5074f3e62e9ae2c2ae8ef9c07a0b4dd3; before 23.11	23.11	Patch available	CNA

hydra VendorNixOS Affected < b72528be5074f3e62e9ae2c2ae8ef9c07a0b4dd3; before 23.11 Fixed in 23.11 Patch available CNA

CPE configurations NVD · 1

CPE	Versions	Role	Vendor
cpe:2.3:a:nixos:hydra::::::::	before 23.11	Vulnerable	NixOS

cpe:2.3:a:nixos:hydra:*:*:*:*:*:*:*:* Versions before 23.11 Vulnerable ·NixOS

Remediation

Fix · CNA hydra (NixOS) Fixed in 23.11

Timeline

2026-10-02 Threatist record created from CVE-2024-32657

References

Patch 1

https://github.com/NixOS/hydra/commit/b72528be5074f3e62e9ae2c2ae8ef9c07a0b4dd3

Advisory 1

https://github.com/NixOS/hydra/security/advisories/GHSA-2p75-6g9f-pqgx

Other 2

TI-2024-30161 Nix Hydra Missing authentication when triggering evaluations CVSS 3.1HIGH 7.5
TI-2025-34598 Hydra missing authentication when triggering evaluations through GitHub and Gitea plugins CVSS 4.0MEDIUM 6.9
TI-2025-34554 Hydra persistent XSS in build metrics CVSS 4.0HIGH 7.1
TI-2025-23506 Hydra no restricted eval after nix-eval-jobs migration CVSS 3.1LOW 2.6

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences