GHSA-g5vf-v6wf-7w2r is a medium-severity (CVSS 5.3) CWE-176 vulnerability in com.google.crypto.tink:tink. A fix is available for com.google.crypto.tink:tink — see the affected versions and patch details below.
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
GHSA-g5vf-v6wf-7w2r by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.
Where this sits among everything scored
Of 385,386 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.
Real-World Exposure
com.google.crypto.tink:tinkReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects Maven packages — download data is not available via public APIs for these ecosystems.
Description
Impact
Tink's Java version before 1.5 under some circumstances allowed attackers to change the key ID part of the ciphertext, resulting in the attacker creating a second ciphertext that will decrypt to the same plaintext. This can be a problem in particular in the case of encrypting with a deterministic AEAD with a single key, and relying on the fact that there is only a single valid ciphertext per plaintext.
No loss of confidentiality or loss of plaintext integrity occurs due to this problem, only ciphertext integrity is compromised.
Patches
The issue was fixed in this pull request.
Workarounds
The only workaround is to backport the fixing pull request.
Details
Tink uses the first five bytes of a ciphertext for a version byte and a four byte key ID. Since each key has a well defined prefix, this extends non-malleability properties (but technically not indistinguishability). However, in the Java version this prefix lookup used a hash map indexed by unicode strings instead of the byte array, which means that invalid Unicode characters would be replaced by U+FFFD by the Java API's default behavior. This means several different values for the five bytes would result in the same hash table key, which allows an attacker to exchange one invalid byte sequence for another, creating a mutated ciphertext that still decrypts (to the same plaintext).
Acknowledgements
We'd like to thank Peter Esbensen for finding this issue and raising it internally.
For more information
If you have any questions or comments about this advisory:
- Open an issue in Tink
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| ☕Maven | com.google.crypto.tink:tink | all versions | 1.5.0com.google.crypto.tink:tink:1.5.0 |
Affected Products
tink javagoogleDetection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for com.google.crypto.tink:tink, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update com.google.crypto.tink:tink to 1.5.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-g5vf-v6wf-7w2r is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
Frequently Asked Questions
Is GHSA-g5vf-v6wf-7w2r in your dependencies?
Find it across Maven, including transitive dependencies.