TI-2026-83258 Aliases CVE-2026-119764 GHSA-m857-xf4f-qjf2

Stored cross-site scripting in Mythic UI via downloaded file preview

HIGH 68CWE-79Published 2026-10-30 · Updated 2026-11-05

Key facts

Attack vector: Network
Privileges required: None
User interaction: Active
Attack complexity: Low
Attack requirements: Present
Impact type: Cross-site scripting
Confidentiality · integrity · availability: High · High · None
Fix status: No fix listed

Attack profile from CVSS 4.0 · CNA. Fix status from CNA. Impact type from CWE-79.

Summary

Mythic from 3.2.16 through 3.4.0.61 contains a stored cross-site scripting vulnerability (CWE-79). Attackers who control files on a target endpoint can plant HTML in files named with a .pdf extension. When an operator downloads such a file and clicks Preview Media, the HTML runs in the Mythic UI origin and can steal localStorage JWTs for full GraphQL and REST access.

Written with Claude Haiku 5.5 from the sources below · 2026-11-05

Description from the CNA

Mythic 3.2.16 through 3.4.0.61 contains a stored cross-site scripting vulnerability that allows attackers controlling target endpoint files to run JavaScript in the Mythic UI origin by planting HTML in .pdf-named files. When an operator downloads the file and clicks Preview Media, content-sniffed HTML from /direct/view renders same-origin, stealing localStorage JWTs for full GraphQL and REST access.

Why it matters now

Exploitation Proof of concept CISA SSVC · not in CISA KEV

EPSS 0.00317 24th percentileScored 2026-11-07

Fix No fix listed No fixed version in the sources yet

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation: Poc
Automatable: No
Technical impact: Total

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
its-a-feature	Mythic	3.2.16 – 3.4.0.61	—	No fix listed	CNA

Mythic Vendorits-a-feature Affected 3.2.16 – 3.4.0.61 Fixed in — No fix listed CNA

CPE names Threatist (inferred) · 1

Inferred from how NVD named this product before; not given by a source.

CPE	Versions	Role	Vendor
cpe:2.3:a:its-a-feature:mythic::::::::	—	—	its-a-feature

cpe:2.3:a:its-a-feature:mythic:*:*:*:*:*:*:*:* Versions — — ·its-a-feature

Remediation

The sources list no fixed version for Mythic.

Written with Claude Haiku 5.5 from the sources below · 2026-11-05

Timeline

2026-10-30 Threatist record created from CVE-2026-119764
2026-10-30 Alias added: GHSA-m857-xf4f-qjf2
2026-11-01 Priority changed: MEDIUM → LOW
2026-11-05 CISA SSVC decision points changed
2026-11-05 Priority changed: LOW → HIGH

References

Patch 1

https://github.com/its-a-feature/Mythic/commit/f06b3ed2d1de6577744cc0b3146966c625685859

Advisory 1

https://github.com/h00die/mythic_xss

Other 2

TI-2026-41717 Mythic < 3.4.0.60 - Broken Permission Filter in payload_build_step Table CVSS 4.0HIGH 7.1
TI-2026-41718 Mythic < 3.4.0.60 - Unauthorized C2 Profile Configuration Access via Unverified Payload UUID CVSS 4.0MEDIUM 6.0
TI-2026-41719 Mythic < 3.4.0.60 - Unauthorized Automation Workflow Modification via eventing_import_automatic_webhook Endpoint CVSS 4.0MEDIUM 5.3

Sources

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