Add NULL checks to prevent segfaults when Kafka metadata contains NULL by k-raina · Pull Request #428 · confluentinc/confluent-kafka-javascript

Kaushik Raina (k-raina) · 2026-01-06T16:57:17Z

Problem

Application crashes with segmentation fault when calling AdminClient.describeTopics() during Kafka broker restarts. The crash occurs when converting node metadata to JavaScript objects.

Root Cause: During broker restarts, Kafka metadata can contain NULL node pointers or NULL host fields. The code dereferenced these NULL pointers without checks, causing segfaults.

Replication steps

Docker Compose environment: Start 3 Kafka brokers + ZooKeeper
Start Client which continuously calls describeTopics() every 500ms on 10 test topics
Run Chaos scripts ( like restart-brokers.sh) to trigger broker restarts/kills
During restarts: Kafka sends metadata updates with changing node information
When brokers go offline: node structures have NULL host fields
Native code converts nodes to JavaScript without NULL checks → segfault

Solution

Added defensive NULL checks in two functions:

ToV8Object() - Check if node pointer and host field are NULL before accessing
FromDescribeTopicsResult() - Check leader, ISR, and replica nodes for NULL before conversion

NULL values are now safely converted to JavaScript null instead of crashing.

Testing

Without Fix

➜  JavaScript_1_3_1_SEG_Fault_Repro-Modifie-2 cat client/logs/stderr.log
=========== Caught a Segmentation Fault [pid=76203] ===========
-----[ Native Stacktraces ]-----
Cannot unwind stacktraces: Feature disabled / Missing libunwind on your system

---[ V8 JavaScript Stacktraces ]---
============================================================

With Fix

  ➜  JavaScript_1_3_1_SEG_Fault_Repro-Modifie-2 cat client/logs/stderr.log
➜  JavaScript_1_3_1_SEG_Fault_Repro-Modifie-2

No segfault noticed

…L values during broker restarts

Copilot

Pull request overview

Adds NULL pointer checks to prevent segmentation faults when Kafka metadata contains NULL values during broker restarts or metadata updates.

Adds NULL checks for node pointers and host fields in ToV8Object()
Adds NULL checks for leader, ISR, and replica nodes in FromDescribeTopicsResult()
Fixes memory leaks by destroying partition lists when validation fails

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Copilot · 2026-01-06T16:57:57Z

src/common.cc

+    if (offsetValue->IsObject()) {
+      v8::Local<v8::Object> offsetObject = offsetValue.As<v8::Object>();
+      int64_t offset = GetParameter<int64_t>(offsetObject, "timestamp", 0);
+      toppar->offset = offset;
+    } else {
+      toppar->offset = 0;
+    }


The logic extracts a 'timestamp' parameter from the offset object but assigns it to toppar->offset. This is confusing - if the parameter name is 'timestamp', consider renaming the local variable to timestamp for clarity, or verify that 'timestamp' is the correct parameter name to extract.

great, it solves an unhandled exception in case you pass an object without the offset property.

…L values during broker restarts

types/kafkajs.d.ts

types/rdkafka.d.ts

Pratyush Ranjan (PratRanj07)

LGTM!

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

Emanuele Sabellico (emasab)

Thanks both! Sent these comments.

types/kafkajs.d.ts

types/rdkafka.d.ts

src/common.cc

types/rdkafka.d.ts

Emanuele Sabellico (emasab) · 2026-02-26T11:11:41Z

src/common.cc

+    if (offsetValue->IsObject()) {
+      v8::Local<v8::Object> offsetObject = offsetValue.As<v8::Object>();
+      int64_t offset = GetParameter<int64_t>(offsetObject, "timestamp", 0);
+      toppar->offset = offset;
+    } else {
+      toppar->offset = 0;
+    }


great, it solves an unhandled exception in case you pass an object without the offset property.

lib/kafkajs/_admin.js

Emanuele Sabellico (emasab)

LGTM. Thanks Kaushik, just run the linter as it's failing in the CI.

Pratyush Ranjan (PratRanj07)

LGTM! Thanks Kaushik Raina (@k-raina) !

add NULL checks to prevent segfaults when Kafka metadata contains NUL…

11a32f8

…L values during broker restarts

Kaushik Raina (k-raina) requested a review from a team as a code owner January 6, 2026 16:57

Copilot AI review requested due to automatic review settings January 6, 2026 16:57

Kaushik Raina (k-raina) requested a review from a team as a code owner January 6, 2026 16:57

Copilot AI reviewed Jan 6, 2026

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Kaushik Raina (k-raina) added 2 commits January 8, 2026 20:23

add NULL checks to prevent segfaults when Kafka metadata contains NUL…

16a22a8

…L values during broker restarts

Add null types to TS

83ed71d

airlock-confluentinc bot force-pushed the kraina-fix-segfault-during-metadata branch from efdc2cf to 83ed71d Compare February 17, 2026 12:40

Pratyush Ranjan (PratRanj07) requested changes Feb 24, 2026

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types/kafkajs.d.ts Outdated Show resolved Hide resolved

types/rdkafka.d.ts Outdated Show resolved Hide resolved

Implement feedback

6bed25e

Pratyush Ranjan (PratRanj07) approved these changes Feb 25, 2026

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Add CHANGELOG entry for v1.8.1 segfault fix

9febe2c

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

Emanuele Sabellico (emasab) requested changes Feb 26, 2026

View reviewed changes

Address feedbacks

6b2c74d

Kaushik Raina (k-raina) requested a review from Emanuele Sabellico (emasab) February 26, 2026 12:52

Emanuele Sabellico (emasab) approved these changes Feb 26, 2026

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Fix lint

ac2d8b1

Pratyush Ranjan (PratRanj07) approved these changes Feb 26, 2026

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Kaushik Raina (k-raina) merged commit b7d191e into master Feb 26, 2026
2 checks passed

Kaushik Raina (k-raina) deleted the kraina-fix-segfault-during-metadata branch February 26, 2026 15:38

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Problem

Replication steps

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Kaushik Raina (k-raina) commented Jan 6, 2026 •

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