# CVE-2026-46385: iskorotkov/avro: CPU Exhaustion in Avro Decoder

> A remote attacker can cause CPU exhaustion and denial of service by sending a crafted Avro payload with a large block count to applications using the vulnerable Go library.

- **Severity:** High 8.7 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 29 May 2026
- **Updated:** 9 Sep 2026
- **Also known as:** CLEANSTART-2026-FR69165, CLEANSTART-2026-JT88657, GHSA-w8j3-pq8g-8m7w, GO-2026-5046, MINI-259m-chq7-227q, MINI-2jgm-x8q5-pg42, MINI-36hr-c7m5-wxfc, MINI-3pgc-p7xc-ffp4, MINI-4fjm-6gxc-gqwg, MINI-69q8-v489-24vv, MINI-6fm5-fgr7-922q, MINI-73jf-fwjf-w3f4, MINI-752g-crmm-9fh8, MINI-8xgj-8w33-h66j, MINI-f623-hghh-h49h, MINI-j6jr-5cx2-qrxx, MINI-mrvx-4x4g-h9f7, MINI-q373-jcwv-fp4h, MINI-rhmw-324p-xhgm, ROOT-APP-GOBINARY-CVE-2026-46385

## What is CVE-2026-46385?

CVE-2026-46385 is a high-severity denial of service vulnerability in iskorotkov avro, published on 29 May 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

iskorotkov/avro is a fast Go Avro codec. Prior to 2.33.0, the Avro array and map decoders looped over an attacker-controlled block-count value without checking the underlying reader's error state inside the loop body. Reader.ReadBlockHeader returns the count as a Go int, which is 64-bit on amd64 / arm64 targets — so a producer can declare a block of up to math.MaxInt64 (~9.2 × 10¹⁸) elements followed by EOF (or any truncated payload), and the decoder will attempt that many no-op iterations before propagating the error. The realistic ceiling is "indefinite until the worker is killed externally" — a single hostile payload pins a CPU core until the process is OOM-killed, deadline-cancelled, or terminated. Remote, unauthenticated denial-of-service. This vulnerability is fixed in 2.33.0.

Weakness: CWE-835 (Loop with Unreachable Exit Condition), CWE-400 (Uncontrolled Resource Consumption)

## Which versions are affected by CVE-2026-46385?

4 open source packages ship an affected version, including github.com/iskorotkov/avro/v2 and github.com/hamba/avro/v2.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `github.com/iskorotkov/avro/v2` | Go | All versions | 2.33.0 |
| `github.com/iskorotkov/avro/v2` | Go | All versions | 2.33.0 |
| `github.com/iskorotkov/avro/v2` | Go | All versions | 2.33.0 |
| `github.com/hamba/avro/v2` | Go | All versions | None |

## How do I fix CVE-2026-46385?

Upgrade github.com/iskorotkov/avro/v2 to 2.33.0 or later.

## Is CVE-2026-46385 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-46385 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-46385 and fix it if it is affected.

What it is: CVE-2026-46385 is a high-severity denial of service vulnerability in iskorotkov avro, published on 29 May 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-46385 exists.

Affected packages and fixed versions:
- github.com/iskorotkov/avro/v2 (Go): affected all versions; fixed in 2.33.0
- github.com/iskorotkov/avro/v2 (Go): affected all versions; fixed in 2.33.0
- github.com/iskorotkov/avro/v2 (Go): affected all versions; fixed in 2.33.0
- github.com/hamba/avro/v2 (Go): affected all versions; no fix listed

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-46385/ (Markdown: https://insights.sbomify.com/CVE-2026-46385/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-46385
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-46385
- OSV: https://osv.dev/vulnerability/CVE-2026-46385

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-46385/
Summaries are generated and may contain mistakes; the official description above is the record.