CVE-2026-63384
Received Received - Intake

Integer Overflow in Libevent Leading to Denial of Service

Publication date: 2026-08-20

Last updated on: 2026-08-20

Assigner: GitHub, Inc.

Description
Libevent is an event notification library. Prior to 2.1.13 and 2.2.2-alpha, libevent has an incorrect integer conversion in event_tagging.c when evtag_unmarshal_header uses evtag_decode_int to decode an attacker-controlled uint32 payload length and returns it as a signed int. Values above INT_MAX become negative or truncated, and evtag_unmarshal_string can use the converted value in allocation sizing, producing a wrapped large allocation request and denial of service. This issue is fixed in versions 2.1.13 and 2.2.2-alpha.

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Meta Information

Published
2026-08-20
Last Modified
2026-08-20
Generated
2026-08-20
AI Q&A
2026-08-20
EPSS Evaluated
N/A
NVD
CVE-2026-63384
EUVD
EUVD-2026-63507

Affected Vendors & Products

Showing 3 associated CPEs
Vendor Product Version / Range
libevent libevent to 2.1.13 (exc)
libevent libevent to 2.2.2-alpha (exc)
libevent libevent to 2.1.13|end_excluding=2.2.2-alpha (exc)

Helpful Resources

Exploitability

CWE
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KEV
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CWE ID Description
CWE-190 The product performs a calculation that can produce an integer overflow or wraparound when the logic assumes that the resulting value will always be larger than the original value. This occurs when an integer value is incremented to a value that is too large to store in the associated representation. When this occurs, the value may become a very small or negative number.

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Executive Summary

CVE-2026-63384 is an integer overflow vulnerability in the libevent library. It occurs in the evtag_unmarshal_header function when decoding a uint32 payload length into a signed int. If the payload length exceeds INT_MAX, the function returns a negative or truncated value. This incorrect value is then used in memory allocation calculations, potentially leading to massive allocation requests and denial of service.

Detection Guidance

To detect this vulnerability, check the installed version of libevent on your system. Run: libevent_version or check package managers like apt list --installed | grep libevent or rpm -qa | grep libevent. If the version is below 2.1.13 or 2.2.2-alpha, the system is vulnerable.

Impact Analysis

This vulnerability can cause denial of service by triggering excessive memory allocation requests. Attackers could craft malicious headers with payload lengths exceeding INT_MAX to crash applications using vulnerable libevent versions. Systems running 32-bit platforms are particularly affected due to the integer overflow behavior.

Compliance Impact

This vulnerability primarily causes denial-of-service conditions due to improper memory allocation, which could disrupt system availability. While it does not directly expose or leak data, prolonged downtime may impact compliance with availability requirements in standards like GDPR (Article 32) or HIPAA (Security Rule). However, no evidence suggests this CVE violates confidentiality or integrity requirements.

Mitigation Strategies

Immediately upgrade libevent to version 2.1.13 or 2.2.2-alpha or later. If upgrading is not possible, apply the patch from the official libevent repository or disable services using libevent until patched.

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