EUVD-2026-29850
GHSA-pxhc-h7q5-6qrg
Attack ChainAIDerived
Hypothetical attack flow derived from CVE metadata – not a confirmed exploit chain
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AccessAuthenticate with low-privilege account
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DeliveryAccess file upload endpoint
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ExploitSubmit crafted filename with '../' sequences
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Executionupload_file() writes outside storage dir
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PersistOverwrite executable/config file
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ImpactAchieve code execution or data tampering
Vulnerability Assessment
| Weakness |
CWE
OWASP Top 10:2025
A01:2025 - Broken Access Control
ASVS 5.0
V5 - File Handling Path canonicalization, traversal prevention
MITRE ATT&CK
2 techniques across 2 tactics: Discovery, Collection The technique list with ATT&CK links and the kill-chain view is part of the Basic plan and up. |
| Exploitation Conditions | Requires a valid authenticated Heym account (CVSS PR:L) able to reach the file upload endpoint, and the ability to control the filename parameter passed to the upload_file() handler with directory-traversal sequences (e.g. '../'). No user interaction is needed (UI:N) and the endpoint is network-reachable (AV:N). Limiting factors: exploitation is gated by authentication, so deployments that do not grant untrusted users upload accounts are far less exposed; impact severity also depends on the OS privileges of the Heym service account and which sensitive paths are writable. Fixed in 0.0.21, so patched instances are not exploitable. |
| Impact | The vendor CVSS 4.0 vector (AV:N/AC:L/AT:N/PR:L/UI:N, VC:L/VI:H/VA:L) scores 7.2 High and is internally consistent with the description: network-reachable, low-complexity, requires low-privilege authentication (PR:L), no user interaction, with high integrity impact (arbitrary file write) and lower confidentiality/availability impact (read/delete). SSVC aligns as Exploitation=poc, Automatable=no, Technical Impact=partial, meaning exploit code exists but the flow is not trivially scriptable at scale. EPSS is very low (0.04%, 11th percentile) and there is no KEV listing, so despite a High CVSS this is not evidence of active mass exploitation - realistic priority is moderate and gated by the need for valid credentials. The signals are broadly consistent; the main caveat is that real-world impact hinges on the privileges of the account running Heym and whether a low-privileged user should have upload rights at all. |
| Exploit ScenarioDerived | An attacker who holds or obtains a low-privileged Heym account submits an upload request with a filename like '../../../../etc/cron.d/evil' or an application config/startup file, causing the server to write attacker-controlled content outside the storage directory. By overwriting a script, configuration, or scheduled-task file that the service later executes, they escalate the file write into code execution or persistent tampering. Public exploit code is reported to exist (SSVC: poc), and the low attack complexity makes the write itself straightforward once authenticated. |
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Alert meAnalysisAIv1 – Jul 23, 2026
Arbitrary file write (and read/delete) in Heym before 0.0.21 lets an authenticated user escape the intended upload storage directory by embedding directory-traversal sequences in the filename parameter of the upload_file() handler. Because the filename is never validated, an attacker with valid credentials can plant, overwrite, or remove files anywhere the service account can reach, potentially leading to code execution or data tampering. Publicly available exploit code exists per SSVC (POC), but EPSS is very low (0.04%, 11th percentile) and it is not on CISA KEV, indicating no confirmed widespread exploitation.
RemediationAI
Vendor-released patch: upgrade to Heym 0.0.21 or later, which contains the 'contain stored upload paths' fix (PR #92, commit 835843e6d2bf7d018cbb8e50f28f0426eaa20c84) - see the release at https://github.com/heymrun/heym/releases/tag/v0.0.21. If immediate upgrade is not possible, reduce exposure by restricting who holds accounts able to reach the upload endpoint (since exploitation requires authentication), and place a reverse-proxy or WAF rule to reject upload requests whose filename parameter contains traversal sequences such as '../', '..\', encoded variants (%2e%2e), or absolute paths; note this filtering can break legitimate filenames and encoded uploads and is only a stopgap. Where feasible, run the Heym service under a low-privilege account with a chroot/jailed or read-only filesystem outside the upload directory to limit the blast radius of an arbitrary write, accepting that this may complicate legitimate file storage. Reference the VulnCheck advisory (https://www.vulncheck.com/advisories/heym-path-traversal-file-upload-via-upload-file) for details.
Affected VersionsENISA
Affected Packages
Source: OSV (Open Source Vulnerabilities)
Affects your stack
Affects 1 package in euvd
Checking this CVE against your own stacks and servers is part of the Basic plan and up.
Technical ContextAI · show details
Heym (vendor heymrun, CPE cpe:2.3:a:heymrun:heym) is an application exposing a file-upload endpoint. The flaw is a classic CWE-22 Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal'): the upload_file() handler concatenates a client-supplied filename onto the server-side storage path without canonicalizing or stripping '../' sequences, so the effective write destination resolves outside the intended directory. The upstream fix (PR #92, commit 835843e6d2bf7d018cbb8e50f28f0426eaa20c84, titled 'fix(files): contain stored upload paths') constrains resolved upload paths, which confirms the root cause was unbounded path resolution rather than a content or MIME issue.
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Severity by source
CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:L/VI:H/VA:L/SC:N/SI:N/SA:N
Network-reachable upload requiring a low-privilege authenticated account (PR:L, AC:L); arbitrary write drives high integrity, with lesser confidentiality/availability from read/delete; no scope change.
Primary rating from Vendor (VulnCheck).
CVSS VectorVendor: VulnCheck
Lifecycle Timeline
2DescriptionCVE.org
Heym before 0.0.21 contains a path traversal vulnerability in the file upload endpoint that allows authenticated users to write attacker-controlled files to arbitrary locations by supplying a crafted filename with traversal sequences. Attackers can exploit the unvalidated filename parameter in the upload_file() handler to bypass path restrictions and write, read, or delete files outside the intended storage directory.
Executive ViewAI
Heym before version 0.0.21 contains a critical file manipulation vulnerability that allows authenticated users to read, write, or delete files outside the intended storage directory, potentially enabling unauthorized code execution or data tampering. This vulnerability directly threatens service integrity and could compromise the confidentiality and availability of business data accessed by the affected Heym deployment.
Apply vendor patch: Upgrade Heym to version 0.0.21 or later. Interim: Restrict network access to Heym service to trusted internal subnets only, implement file integrity monitoring on directories accessible by the Heym service account, and enforce multi-factor authentication on all accounts with Heym access.
Threat Intelligence Overview
NVD
CVE.org
EPSS
Vulnrichment
VulDB
How this decision was reached
The engine reads each signal below and applies a fixed list of rules from top to bottom. The first rule that matches sets the recommended action – like a statement, every line is shown.
What every action level means
SSVC AssessmentENISA
Priority Score
Attack Technique
Path traversal exploits occur when applications use user-controlled input to construct file system paths without proper validation.
Malicious file upload attacks exploit insufficient validation when web applications accept user-provided files.
Authenticated users with workflow create/edit rights on self-hosted Heym deployments prior to 0.0.40 can escape the appl
Sandbox escape in the heym workflow platform before 0.0.91 allows an authenticated user who can author or edit workflow
Python eval()-based remote code execution in Heym (heymrun/heym) before 0.0.53 lets an authenticated user who can edit a
Sandbox escape in Heym's custom Python tool executor (versions before 0.0.21) allows authenticated workflow authors to b
Heym deployments prior to 0.0.53 leave their Telegram webhook endpoints without verification of the X-Telegram-Bot-Api-S
Forged Slack webhook events can trigger Heym workflows with the owner's credentials because Heym before 0.0.53 skips Sla
Non-blind server-side request forgery in heym (heymrun) before 0.0.109 lets any registered user redirect backend HTTP re
Authorization bypass in Heym's workflow execution engine (versions before 0.0.21) allows any authenticated user to run w
Credential exfiltration in Heym before version 0.0.106 allows an authenticated collaborator who has been granted shared
Cleartext storage and over-exposure of multiple capability secrets in Heym, a workflow automation platform, affects all
heym before 0.0.105 fails to enforce credential authorization in its Redis workflow node, letting an authenticated workf
Server-side request forgery in Heym 0.0.90 and earlier lets a caller-controlled workflow input steer an outbound HTTP fe
Exploit-DB