Protobuf: Denial of Service issue through malicious messages containing negative varints or deep recursion
### Impact A Denial of Service (DoS) vulnerability exists in the Protobuf PHP library during the parsing of untrusted input. Maliciously structured messages—specifically those containing negative `varint`s or deep recursion—can be used to crash the application, impacting service availability. ### Patches Patches have been released to 5.34.0-RC1 and 4.33.6.
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describes (1)
Related CVEs.
| ID | severity | exploitable | ||
|---|---|---|---|---|
| CVE-2026-6409US | — | — | ||
A Denial of Service (DoS) vulnerability exists in the Protobuf PHP library during the parsing of untrusted input. Maliciously structured messages—specifically those containing nega… | ||||
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references
External citations — patches, advisories, analysis.
- https://github.com/protocolbuffers/protobufPACKAGE
- https://github.com/protocolbuffers/protobuf/commit/60e93d2d104f2af9cd345b1c6f3891d91430244aWEB
- https://github.com/protocolbuffers/protobuf/commit/c8e9b27d95c6ab2d0668b5889e7dac2c477b7038WEB
- https://github.com/protocolbuffers/protobuf/issues/24159WEB
- https://github.com/protocolbuffers/protobuf/issues/25067WEB
- https://github.com/protocolbuffers/protobuf/security/advisories/GHSA-p2gh-cfq4-4wjcWEB
- https://nvd.nist.gov/vuln/detail/CVE-2026-6409ADVISORY
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