CVE-2026-119078

Apache Commons Codec: Blake3 doFinalize is stateless; the documented KDF example derives identical keys

Published Nov 9, 2026 CVSS 3.1 · 9.1 Critical EPSS < 1% KEV · Not listed
Description
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.

Remediation

No solution or workaround provided in the CVE record

Tracking

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Advisories

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History
Type Values Removed Values Added
Metrics cvssV3_1

{'score': 9.1, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N'}

Type Values Removed Values Added
First Time appeared Apache
Apache commons Codec
Vendors & Products Apache
Apache commons Codec
Type Values Removed Values Added
Description 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.
Title Apache Commons Codec: Blake3 doFinalize is stateless; the documented KDF example derives identical keys
Weaknesses CWE-1068
CWE-684
References
Weaknesses

Sources

Status
PUBLISHED
Assigner
apache
Published
Updated
Nov 12, 2026, 5:34 PM
Reserved
Oct 29, 2026, 1:10 PM
Status
Awaiting Analysis
Published
Nov 9, 2026, 8:18 PM
Modified
Nov 12, 2026, 6:17 PM