Denial of Service (DoS) vulnerability exists in the Protobuf PHP library during the parsing of untrusted input
Priority LOW 31CWE-20Published · Updated
Key facts
- Attack vector
- Network
- Privileges required
- None
- User interaction
- Passive
- Attack complexity
- Low
- Attack requirements
- None
- Impact type
- Denial of service
- Confidentiality · integrity · availability
- None · None · High
- Fix status
- Fixed
Attack profile from CVSS 4.0 · CNA. Fix status from CNA and GitHub. Impact type from CWE-400.
Summary
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 varints or deep recursion—can be used to crash the application, impacting service availability.
Why it matters now
Exploitation None reported CISA SSVC · not in CISA KEV
EPSS 0.0036 29th percentileScored 2026-11-07
Fix Fixed Protobuf-php (Pecl) (Protocol Buffers): 5.34.0-RC1, 4.33.6google/protobuf (Packagist): 4.33.6
SSVC decision points
CISA ADP · SSVC 2.0.3
- Exploitation
- None
- Automatable
- No
- Technical impact
- Partial
The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.
Affected products
| Vendor | Product | Affected versions | Fixed in | Status | Source |
|---|---|---|---|---|---|
| protocolbuffers | Protobuf-php (Pecl) | before 5.34.0-RC1; before 4.33.6 | 5.34.0-RC1, 4.33.6 | Patch available | CNA |
| — | google/protobuf (Packagist) | before 4.33.6 | 4.33.6 | Patch available | GHSA-p2gh-cfq4-4wjc |
- Protobuf-php (Pecl) Vendorprotocolbuffers Affected before 5.34.0-RC1; before 4.33.6 Fixed in 5.34.0-RC1, 4.33.6 Patch available CNA
- google/protobuf (Packagist) Vendor— Affected before 4.33.6 Fixed in 4.33.6 Patch available GHSA-p2gh-cfq4-4wjc
Remediation
- Fix · CNA Protobuf-php (Pecl) (Protocol Buffers) Fixed in 5.34.0-RC1, 4.33.6
- Fix · GHSA-p2gh-cfq4-4wjc google/protobuf (Packagist) Fixed in 4.33.6 Advisory →
Timeline
- 2026-10-02 Threatist record created from CVE-2026-6409
- 2026-10-03 Alias added: GHSA-p2gh-cfq4-4wjc
References
Other 6
- https://github.com/protocolbuffers/protobuf/security/advisories/GHSA-p2gh-cfq4-4wjc
- https://github.com/protocolbuffers/protobuf/issues/24159
- https://github.com/protocolbuffers/protobuf/issues/25067
- https://github.com/protocolbuffers/protobuf/commit/60e93d2d104f2af9cd345b1c6f3891d91430244a
- https://github.com/protocolbuffers/protobuf/commit/c8e9b27d95c6ab2d0668b5889e7dac2c477b7038
- https://github.com/protocolbuffers/protobuf
Sources
- CVE-2026-6409 · CVE Program
- CVE-2026-6409 · NVD
- FIRST EPSS
- GHSA-p2gh-cfq4-4wjc · GitHub Advisory Database · CC BY 4.0
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