---
id: GO-2026-5048
aliases:
  - GHSA-mx64-mj3q-7prj
title: >-
  Denial of service via unbounded map allocations in
  github.com/iskorotkov/avro/v2 and github.com/hamba/avro/v2
summary: >-
  Denial of service via unbounded map allocations in
  github.com/iskorotkov/avro/v2 and github.com/hamba/avro/v2
severity: none
vendor: iskorotkov
product: github.com/iskorotkov/avro/v2
ecosystem: go
affected:
  - github.com/iskorotkov/avro/v2 < 2.33.0
  - github.com/hamba/avro/v2
patched:
  - github.com/iskorotkov/avro/v2 2.33.0
published: '2026-07-27'
updated: '2026-07-27'
source: OSV
sourceUrl: 'https://osv.dev/vulnerability/GO-2026-5048'
references:
  - url: 'https://github.com/iskorotkov/avro/security/advisories/GHSA-mx64-mj3q-7prj'
  - url: >-
      https://github.com/iskorotkov/avro/commit/5192df96a158999344ac96ebcb1f7461d626f6d7
tags:
  - osv
  - go
ingestedAt: '2026-07-27T19:08:55.723Z'
---

## Overview

The Avro map decoder accepts attacker-controlled block-element counts from the wire format and grows the destination map without enforcing an upper bound. A producer can declare an arbitrarily large map (in one block, or chunked across many sub-limit blocks) and exhaust process memory until the OOM killer fires.

The fix introduces Config.MaxMapAllocSize with cumulative enforcement across block boundaries. The new limit is opt-in: the field defaults to zero, which preserves the previous unbounded behavior for backward compatibility. Upgrading to v2.33.0 alone does not mitigate the issue; consumers of untrusted Avro data must explicitly set MaxMapAllocSize on their avro.Config.

## Affected packages

- `github.com/iskorotkov/avro/v2 < 2.33.0`
- `github.com/hamba/avro/v2`

## Remediation

Upgrade to a patched release:

- `github.com/iskorotkov/avro/v2 2.33.0`