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.
Published: 2026-11-09
Score: n/a
EPSS: n/a
KEV: No
Impact: Inaccurate key derivation resulting in identical keys
Action: Assess and Fix
AI Analysis

Impact

The Blake3 class in Apache Commons Codec incorrectly documents that consecutive doFinalize calls produce different results, while the implementation returns the same output each time. Code that expects new derived keys after each doFinalize therefore obtains identical keys, breaking separation between keys. This flaw can compromise confidentiality by providing attackers with predictable or duplicate keys derived from secrets.

Affected Systems

Apache Commons Codec library versions ranging from 1.16.0 up to, but not including, 1.23.0 are impacted. The defect exists in the implementation regardless of the host platform or programming language. Users employing these versions within any application that performs repeated doFinalize calls on the same Blake3 instance are potentially affected.

Risk and Exploitability

The vulnerability is a logical design flaw and does not expose a traditional attack vector such as remote code execution. No exploitation metrics like CVSS or EPSS are available, and the issue is not listed in the KEV catalog. The primary risk arises from developers incorrectly using the API, leading to identical keys and weakened cryptographic safeguards.

Generated by OpenCVE AI on November 9, 2026 at 21:17 UTC.

Remediation

No solution or workaround provided in the CVE record.

OpenCVE Recommended Actions

  • Examine your code for repeated doFinalize calls on a single Blake3 instance and modify logic to request a combined length in one call, then split the resulting output into separate keys as shown in the updated Javadoc. Alternatively instantiate a new Blake3 object for each key derivation.
  • Upgrade Apache Commons Codec to version 1.23.0 or later; note that upgrading alone does not fix affected code, so also apply the logic changes above.
  • Verify that derived keys are distinct by performing cryptographic checks or tests; add unit tests to assert that successive keys differ when derived from the same input data.

Generated by OpenCVE AI on November 9, 2026 at 21:17 UTC.

Tracking

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History

Mon, 09 Nov 2026 20:15:00 +0000

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

Subscriptions

No data.

cve-icon MITRE

Status: PUBLISHED

Assigner: apache

Published:

Updated: 2026-11-09T20:11:12.230Z

Reserved: 2026-10-29T13:10:03.787Z

Link: CVE-2026-119078

cve-icon Vulnrichment

No data.

cve-icon NVD

Status : Received

Published: 2026-11-09T20:18:04.697

Modified: 2026-11-09T20:18:04.697

Link: CVE-2026-119078

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

Updated: 2026-11-09T21:30:11Z

Weaknesses
  • CWE-1068

    Inconsistency Between Implementation and Documented Design

  • CWE-684

    Incorrect Provision of Specified Functionality