Quick answers
- Is This vulnerability exploited in the wild?
- No. Junglewise Threat Intelligence has no report of This vulnerability being exploited in the wild.
- How severe is This vulnerability?
- High severity, with a CVSS score of 7.5, published 18 May 2026.
- Which products and versions are affected?
- github.com/iskorotkov/avro/v2 (Go) < 2.33.0; Hamba Avro/V2 <= v2.31.0.
- Is there a fix for This vulnerability?
- A patch was published on 2026-04-30: Fix introduced in PR #5 Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
- How is This vulnerability attacked?
- It is attacked over the network, in a software library.
- Am I affected?
- Check whether you run github.com/iskorotkov/avro/v2 (Go) or Hamba Avro/V2 at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.
Technical details
The Avro map decoder in `codec_map.go` (specifically `mapDecoder.Decode` and `mapDecoderUnmarshaler.Decode`) fails to enforce an upper bound on attacker-controlled block-element counts. An attacker can provide a large element count in a single block or across multiple chunked blocks, causing the decoder to pre-allocate or grow a map until the process exhausts available memory (OOM). The vulnerability is present in the archived `hamba/avro` and its fork `iskorotkov/avro`. The fix in `iskorotkov/avro` v2.33.0 introduces `Config.MaxMapAllocSize` to track cumulative entry counts, but this protection is opt-in and must be explicitly configured to a non-zero value to mitigate the risk.
Affected products
- hamba avro/v2 <= v2.31.0
- iskorotkov avro/v2 < v2.33.0
Timeline
- 2026-04-30: patched: Fix introduced in PR #5
- 2026-05-06: advisory: v2.33.0 released
- 2026-05-07: disclosed: Initial advisory publication