What’s Vulnerable › Vulnerabilities

CVE-2020-8929: Ciphertext integrity weakness in Tink

• Severity: medium (CVSS 5.3 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.5% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2020-10-19 · updated 2026-06-17
• Weakness: CWE-176

Description

A mis-handling of invalid unicode characters in the Java implementation of Tink versions prior to 1.5 allows an attacker to change the ID part of a ciphertext, which result in the creation of a second ciphertext that can decrypt to the same plaintext. This can be a problem with encrypting deterministic AEAD with a single key, and rely on a unique ciphertext-per-plaintext.

Affected products

• Google LLC Tink: before 1.5.0 — fixed in 1.5.0

How to fix

Upgrade to a fixed version: Google LLC Tink 1.5.0. Check the vendor advisory for mitigations.

References

• https://github.com/google/tink/commit/93d839a5865b9d950dffdc9d0bc99b71280a8899
• https://github.com/google/tink/security/advisories/GHSA-g5vf-v6wf-7w2r
• https://github.com/google/tink/commit/93d839a5865b9d950dffdc9d0bc99b71280a8899
• https://github.com/google/tink/security/advisories/GHSA-g5vf-v6wf-7w2r

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