Bug 2570553 (CVE-2026-119078)

Summary: CVE-2026-119078 commons-codec/commons-codec: commons-codec: Cryptographic key reuse via repeated Blake3 finalization
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
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A flaw was found in Apache Commons Codec. Misleading documentation and examples in the Blake3 cryptographic hashing component incorrectly suggest that consecutive finalization calls produce distinct output. In practice, calling the finalization method repeatedly without supplying new data returns identical bytes. Applications relying on this pattern to derive multiple secret keys generate duplicate keys instead, which can allow attackers to compromise cryptographic protections and gain unauthorized access to encrypted data.
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Description OSIDB Bzimport 2026-11-10 20:06:35 UTC 
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.