Metalama allows local code execution through DLL planting in shared temporary directories (CVE-2026-62847)
Published Last modified Sources: CVE.org, OSV, Hersteller
What is affected, what to do
Metalama is a Roslyn-based open-source patterns and architecture toolkit for C#. Prior to 2025.1.18, 2026.0.25 and 2026.1.19, Metalama.Framework and Metalama.Tool load and execute compile-time assemblies, auxiliary executable tools and embedded helper assemblies from predictable temporary directories.
Update Metalama to version 2025.1.18.
- Affected
- Metalama
gte 2025.2.0-preview, <= 2025.2.5-rc..* - Metalama
lt *..2025.1.18
- Metalama
- Fixed in
- Metalama
2025.1.18
- Metalama
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Metrics
8.2
Priority
XIEM Effective CVSS: highest available CVSS rating from NVD and vendor data.
Source: Vendor (CNA), CVSS v3
8.2
CVSS v3
Severity High on the scale from 0 to 10.
Source: CVE.org, OSV, Hersteller
0.2 %
EPSS score
Low — model estimates < 1% exploitation likelihood.
Source: FIRST EPSS, percentile 4.3
Show all metrics
- Severity
- High
Priority (0–325)
The priority score is a consolidated metric that condenses several individual signals into a single, action-guiding ranking: technical severity (CVSS), exploitation likelihood (EPSS), known-exploited status (KEV) and the context of the affected asset. The aim is to answer the only truly important question in vulnerability management: what first?
Read in glossary- 71.15 Methodology
Exploit maturity
An exploit is code or a technique that specifically uses a concrete vulnerability to force unintended behaviour — such as executing code or escalating privileges. It is the tool that turns a theoretical flaw into a practical attack.
Read in glossary- no public PoC known
XIEM Effective CVSS
XIEM® is the tiered managed-security operating model from NEOSEC and a registered trademark of NEOSEC GmbH. It extends classic SIEM — the central collection, normalisation and correlation of security-relevant events — with endpoint forensics, network visibility and deception technology, and consolidates them into three building tiers: Sentry, Orchestrate and Command.
Read in glossary- 8.2 Methodology
CVSS v3
CVSS is the globally established, open standard for assessing the technical severity of a vulnerability on a scale from 0 to 10. It describes how easily a flaw can be exploited and what damage it can cause — but not how likely its actual exploitation is. CVSS and the complementary EPSS deliberately answer different questions.
Read in glossary- 8.2
EPSS score
The EPSS score is the absolute model output for an individual vulnerability: the estimated probability of real-world exploitation within the next 30 days, expressed as a value between 0 and 1 (i.e. 0 % to 100 %). A score of 0.42 means „the model estimates a 42 % chance of real-world exploitation within 30 days“.
Read in glossary- 0.2 %
- Low — model estimates < 1% exploitation likelihood.
EPSS percentile
The EPSS percentile is the relative position of a vulnerability within all EPSS-scored CVEs, expressed as a value between 0 and 1. A percentile of 0.90 means „this CVE has a higher EPSS score than 90 % of all other scored CVEs“. Unlike the EPSS score, it is not a probability — but a positioning within a ranking.
Read in glossary- 4.3
- Low — this CVE sits in the lower 10% of all CVEs scored today.
KEV status
The KEV catalogue is a list maintained by the US authority CISA of vulnerabilities for which active exploitation in the wild has been confirmed. It answers not the question „how severe?“ but „is it already being attacked?“ — thereby sharply prioritising patching.
Read in glossary- —
- Published
- CISA assessment (SSVC)
- Exploitation: none known · not automatable · Technical impact: total
- Source: CISA Vulnrichment, as of 30 October 2026
CWE
CWE is a catalogue of typical weakness types in software and hardware — such as flawed input validation, unsafe memory handling or poor authentication. Where a CVE names a concrete vulnerability in a concrete product, a CWE describes the underlying class of defect.
Read in glossary- CWE-377, CWE-427
Detection rules
No NEOSEC detection rule is available for this vulnerability yet.
Classification under NIS2 and CRA
Rule-based classification from exploitation status and severity. It does not replace a case-by-case assessment.
NIS2
NIS2 is EU Directive (EU) 2022/2555 to raise the level of cybersecurity across the Union. It substantially broadens obligations compared with the first NIS directive: more sectors, mandatory risk management, staged reporting duties and personal accountability of senior management.
Read in glossary- High technical severity: assess and remediate the vulnerability in vulnerability handling under Art. 21(2)(e) NIS2 and document the decision.
CRA
The CRA is EU Regulation (EU) 2024/2847 setting horizontal cybersecurity requirements for „products with digital elements“ — from industrial controllers and software to connected consumer devices. For the first time manufacturers must ensure security across the entire product lifecycle, handle vulnerabilities and provide security updates.
Read in glossary- From 11.12.2027, Annex I Part II CRA requires manufacturers of affected products with digital elements to handle vulnerabilities without delay and provide security updates.
ISO/IEC 27001
ISO/IEC 27001 is the internationally leading standard for an information security management system (ISMS). It describes a risk-based, process-oriented framework to systematically plan, implement, review and improve information security.
Read in glossary- Control A.8.8, management of technical vulnerabilities: assess relevance to your systems, plan remediation and keep evidence.
Description
Metalama is a Roslyn-based open-source patterns and architecture toolkit for C#. Prior to 2025.1.18, 2026.0.25 and 2026.1.19, Metalama.Framework and Metalama.Tool load and execute compile-time assemblies, auxiliary executable tools and embedded helper assemblies from predictable temporary directories. On `Linux` and `macOS`, the default `Path.GetTempPath()` location is world-writable, and existing artifacts are trusted based on sentinel or `.completed` marker files rather than integrity verification. A local unprivileged user on a shared machine or CI/build agent can pre-create the deterministic directory structure and plant a malicious DLL with the matching sentinel. When a higher-privileged developer or build account subsequently builds, Metalama skips regeneration and executes the planted artifact in the compiler, IDE or MSBuild process as the building user. This permits cross-user privilege escalation, reading source and secrets, supply-chain tampering with build output, or disrupting builds. Default Windows per-user temporary directories are protected by ACLs and are not affected. Deployer-selected insecure cache locations are outside the vulnerability's scope. This issue is fixed in versions 2025.1.18, 2026.0.25 and 2026.1.19.
Source: cvelistv5, NVD (NIST), CVE.org (MITRE), OSV (Open Source Vulnerabilities), GitHub Security Advisories
Affected products
The following versions are affected. Older releases of the same product line are also vulnerable unless stated otherwise.
| Affected versions | Fixed in | ||
|---|---|---|---|
| metalama | Metalama |
|
|
| nuget | metalama.framework |
|
|
Weakness classes (CWE)
CWE-377Insecure Temporary File
Class
Creating and using insecure temporary files can leave application and system data vulnerable to attack.
Entry at MITRE CWE-377CWE-427Uncontrolled Search Path Element
Base
The product uses a fixed or controlled search path to find resources, but one or more locations in that path can be under the control of unintended actors.
Entry at MITRE CWE-427
References & sources
- github.commetalama/Metalama/security/advisories/GHSA-m6wq-39m7-9xppweb, x_refsource_CONFIRM
- github.commetalama/Metalama/pull/1719web
- github.commetalama/Metalama/commit/09911349a916e82194b1cfaa6d0a38acad928f…web, x_refsource_MISC
- github.commetalama/Metalama/commit/92c4feecfce86d18fcb007ab6d3a1b4383326a…web, x_refsource_MISC
- github.commetalama/Metalama/commit/ab9407263203c66d7c5680a34c28dba31f9951…web
- github.commetalama/Metalamapackage
- github.commetalama/Metalama/pull/1650x_refsource_MISC
- github.commetalama/Metalama/releases/tag/release/2025.1.18x_refsource_MISC
- github.commetalama/Metalama/releases/tag/release/2026.0.25x_refsource_MISC
- github.commetalama/Metalama/releases/tag/release/2026.1.19x_refsource_MISC
Changes to this CVE
Who changed this CVE and when: NVD (analysis, affected products, CVSS), the CVE publisher (CNA) and additional providers such as CISA (ADP).
Record modifiedCISA ADP
CISA assessment (SSVC): exploitation: none known, automatable: no
Show the original change
Individual changes of this event as published by NVD Type Action Before After SSVC assessment added —{"id":"CVE-2026-62847","role":"CISA Coordinator","options":[{"exploitation":"none"},{"automatable":"no"},{"technicalImpact":"total"}],"version":"2.0.3","timestamp":"2026-10-30T21:21:14.933972Z"}Source identifier: 134c704f-9b21-4f2e-91b3-4a467353bcc0
ReceivedGitHub
CVSS V3.1: AV:L/AC:L/PR:L/UI:R/S:C/C:H/I:H/A:H
Weakness type: CWE-427, CWE-377
Description added or changed
New references:- https://github.com/metalama/Metalama/commit/09911349a916e82194b1cfaa6d0a38acad928fc9
- https://github.com/metalama/Metalama/commit/92c4feecfce86d18fcb007ab6d3a1b4383326a2e
- https://github.com/metalama/Metalama/pull/1650
- https://github.com/metalama/Metalama/releases/tag/release/2025.1.18
and 3 more references
Show 12 original changes
Individual changes of this event as published by NVD Type Action Before After Description added —Metalama is a Roslyn-based open-source patterns and architecture toolkit for C#. Prior to 2025.1.18, 2026.0.25 and 2026.1.19, Metalama.Framework and Metalama.Tool load and execute compile-time assemblies, auxiliary executable tools and embedded helper assemblies from predictable temporary directories. On `Linux` and `macOS`, the default `Path.GetTempPath()` location is world-writable, and existing artifacts are trusted based on sentinel or `.completed` marker files rather than integrity verification. A local unprivileged user on a shared machine or CI/build agent can pre-create the deterministic directory structure and plant a malicious DLL with the matching sentinel. When a higher-privileged developer or build account subsequently builds, Metalama skips regeneration and executes the planted artifact in the compiler, IDE or MSBuild process as the building user. This permits cross-user privilege escalation, reading source and secrets, supply-chain tampering with build output, or disrupting builds. Default Windows per-user temporary directories are protected by ACLs and are not affected. Deployer-selected insecure cache locations are outside the vulnerability's scope. This issue is fixed in versions 2025.1.18, 2026.0.25 and 2026.1.19.CVSS added —AV:L/AC:L/PR:L/UI:R/S:C/C:H/I:H/A:HWeakness type (CWE) added —CWE-427Weakness type (CWE) added —CWE-377Affected versions (publisher) added —New affected value received. <a href="https://github.com/CVEProject/cvelistV5/blob/main/cves/2026/62xxx/CVE-2026-62847.json">CVE-2026-62847</a>Reference added —https://github.com/metalama/Metalama/commit/09911349a916e82194b1cfaa6d0a38acad928fc9Reference added —https://github.com/metalama/Metalama/commit/92c4feecfce86d18fcb007ab6d3a1b4383326a2eReference added —https://github.com/metalama/Metalama/pull/1650Reference added —https://github.com/metalama/Metalama/releases/tag/release/2025.1.18Reference added —https://github.com/metalama/Metalama/releases/tag/release/2026.0.25Reference added —https://github.com/metalama/Metalama/releases/tag/release/2026.1.19Reference added —https://github.com/metalama/Metalama/security/advisories/GHSA-m6wq-39m7-9xppSource identifier: security-advisories@github.com
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