CVE-2026-12043 - Heap double-free in AWS Common Runtime aws-c-http

unknownCVE-2026-12043

Bulletin ID: 2026-043-AWS Scope: AWS Content Type: Important (requires attention) Publication Date: 06/12/2026 11:45 AM PDT Description: AWS Common Runtime aws-c-http is a HTTP client library used by AWS SDKs for handling http requests to AWS services. We identified CVE-2026-12043, an issue where improper handling of HPACK dynamic table size updates in the AWS Common Runtime aws-c-http library might allow a remote actor operating a server to cause memory corruption on a connecting client application, potentially leading to arbitrary code execution, via a crafted sequence of HTTP/2 HEADERS frames. Impacted versions: aws-c-http >= 0.4.22 AND <= 0.10.15 Exposed in following sdk versions: - aws-sdk-cpp >= 1.11.41, <= 1.11.814 - aws-sdk-java-v2 >= 2.44.27, <= 2.44.14 Please refer to the article below for the most up-to-date and complete information related to this AWS Security Bulletin.

CSIRTS triage

vendor: AWS product: aws-c-http Memory corruption Remote code executionaffected: >= 0.4.22 AND <= 0.10.15

What: Improper handling of HPACK dynamic table size updates may lead to memory corruption and potential arbitrary code execution.
Who is affected: Users of aws-c-http within the specified version range.
Urgency: Remediation is urgent due to the potential for remote code execution.
Action: Update aws-c-http to a version outside the affected range.

AI-assisted analysis generated from the source advisory — verify against the original.

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Details

Source: AWS Security Bulletins (INTL · vendor-psirt · site)
Severity: unknown
Published: 2026-08-20
Exploitation: Not in CISA KEV at last sync

Original advisory: https://aws.amazon.com/security/security-bulletins/rss/2026-043-aws/

Exploitation outlook

EPSS (FIRST.org) estimates each CVE’s probability of exploitation in the next 30 days — here is the CSIRTS.com read on those numbers.

Low exploitation riskCVE-2026-120430.35% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 28% of all EPSS-scored CVEs.

Referenced CVEs

CVE	CSIRTS overview	External
CVE-2026-12043	coverage & exploitation status	NVD · CVE.org

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