CVE-2026-74757 Apache Software Foundation CVE debrief

Who should care

System administrators and security teams responsible for Apache bRPC deployments should assess exposure and verify the fix to prevent potential denial-of-service attacks. This includes reviewing the current deployment configurations, identifying potential vulnerabilities, and implementing necessary mitigations. Additionally, security teams should monitor for suspicious activity and review compensating controls for exposed systems while remediation is being

Why it matters

Defenders should prioritize upgrading to Apache bRPC version 1.18.0 or applying the provided patch to prevent potential denial-of-service attacks. System administrators and security teams responsible for bRPC deployments should assess exposure and verify the fix.

• Potential denial-of-service attacks through memory exhaustion
• Verification of fix required to prevent exploitation
• Upgrade or patching necessary to mitigate vulnerability
• Monitoring for suspicious activity recommended

Technical summary

The Apache bRPC mcpack2pb parser trusts the item count stored in the mcpack array header without validating it against the actual payload size. This allows remote attackers to make the server allocate a large amount of memory via a crafted mcpack request with a huge array item count. The vulnerability affects Apache bRPC servers that use a NsheadService with UbrpcMcpack2Adaptor and parse requests with code generated by the mcpack2pb protoc plugin. A crafted request can force the server to preallocate about 16GB of virtual memory, potentially aborting the process on memory-constrained hosts.

Defensive priority

Defenders should prioritize upgrading to Apache bRPC version 1.18.0 or applying the provided patch to prevent potential denial-of-service attacks. System administrators and security teams responsible for bRPC deployments should assess exposure and verify the fix.

Recommended defensive actions

• Upgrade to Apache bRPC version 1.18.0
• Apply the provided patch
• Assess exposure and verify the fix
• Monitor for potential denial-of-service attacks
• Review compensating controls for exposed systems while remediation is scheduled and verified
• Check relevant monitoring, detection, and logs for exposed assets that need extra review
• Track exceptions, retest remediated assets, and close the item only after evidence is documented

Evidence notes

The CVE record and source item provide details on the vulnerability, including the root cause, affected scenarios, and recommended fixes. However, there is limited information on actual exploitation or victim impact.

Sources and references

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.