---
id: "CVE-2026-119078"
page: "https://infrastack.ai/live/CVE-2026-119078"
kind: "vulnerability"
aliases: ["CVE-2026-119078"]
title: "Apache Commons Codec: Blake3 key derivation returns identical keys on repeated calls"
severity: "low"
cvss: null
epss: null
exploited: false
status: "open"
category: "package"
products: []
ecosystems: []
tags: ["apache-commons-codec", "blake3", "java", "key-derivation", "package"]
not_affected_if: ["no-blake3-usage", "single-dofinalize-per-instance"]
published_at: "2026-11-09T20:18:04+00:00"
first_seen_at: "2026-11-09T20:48:12+00:00"
updated_at: "2026-11-09T20:50:05+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-119078", "first_seen_at": "2026-11-09T20:48:12+00:00"}]
exploit_sources: []
---

# Apache Commons Codec: Blake3 key derivation returns identical keys on repeated calls

Link for people: https://infrastack.ai/live/CVE-2026-119078 (this .md is for agents)

The Blake3 class in Apache Commons Codec documented that repeated doFinalize calls return different output, but they return the same bytes. An application that derives several keys with consecutive doFinalize calls ends up with identical keys, so the separation between them is lost.

_Summary, check and fix written by a model from the sources; labelled as such._

## How to check

- Search your code for `Blake3` and for more than one `doFinalize` call on the same instance.
- Check the Commons Codec version in your build file: affected range is `1.16.0` up to but not including `1.23.0`.

## Fix

- Apache Commons Codec: move to `1.23.0` or later, which corrects the documentation only.
- Upgrading alone does not fix affected code; derive multiple keys in one call with the combined length and split the output, as the updated Javadoc shows.

## Timeline

- 2026-11-09T20:48:12+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-119078

## From the sources

Apache Commons Codec's Blake3 class documented the output of its doFinalize methods as depending on any previously finalized bytes, so that consecutive calls would return different output. In fact, doFinalize does not change the hash state: calling it again without supplying more input returns the same bytes. The key-derivation example in the class Javadoc, shipped since 1.16.0, derives two keys with two consecutive doFinalize calls. Code that follows it gets identical keys, so the separation between the derived keys is lost. The same applies to any application that calls doFinalize more than once on one instance and expects new output each time.



This issue affects Apache Commons Codec from 1.16.0 before 1.23.0.



Version 1.23.0 corrects the documentation, but the behavior of doFinalize is unchanged. Upgrading alone does not fix affected code. Users should check their applications for repeated doFinalize calls on the same Blake3 instance and derive multiple keys by requesting the combined length in one call and splitting the output, as the updated Javadoc shows.

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