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.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
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.
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 | 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.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2026-46385 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-46385 exists.
Sources
Also known as CLEANSTART-2026-FR69165, CLEANSTART-2026-JT88657, GHSA-w8j3-pq8g-8m7w, GO-2026-5046, MINI-259m-chq7-227q, MINI-2jgm-x8q5-pg42 and 14 more.