CVE-2026-63388Public exploit

Heap overwrite via AF_UNIX address copy

Published Aug 20, 2026 · Updated Aug 20, 2026

Heap out-of-bounds write in Libevent before 2.1.13 and 2.2.2-alpha allows local users to corrupt heap memory via AF_UNIX accept. In bufferevent_sock.c, bufferevent_socket_set_conn_address_ copies the kernel-reported peer sockaddr length into the 28-byte conn_address field with memcpy after an EVUTIL_ASSERT check that disappears in NDEBUG release builds. Exposure requires an AF_UNIX listener that reaches the evhttp accept path; a connecting local peer can overwrite the adjacent dns_request pointer and nearby heap data, causing a crash and potentially further memory-corruption impact.

CVSS severity8.4
High
EPSS probability0.14%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Heap out-of-bounds write in Libevent before 2.1.13 and 2.2.2-alpha allows local users to corrupt heap memory via AF_UNIX accept. In bufferevent_sock.c, bufferevent_socket_set_conn_address_ copies the kernel-reported peer sockaddr length into the 28-byte conn_address field with memcpy after an EVUTIL_ASSERT check that disappears in NDEBUG release builds. Exposure requires an AF_UNIX listener that reaches the evhttp accept path; a connecting local peer can overwrite the adjacent dns_request pointer and nearby heap data, causing a crash and potentially further memory-corruption impact.

The record

CVE
CVE-2026-63388
Published
Aug 20, 2026
Updated
Aug 20, 2026
Vendor
Libevent
Product
Libevent
Classifications
CWE-787, CWE-617
Attack vector
local
Privileges
unauthenticated

Timeline

How it unfolded

  1. Aug 20, 2026CVE publishedPublication date reported by the CVE source.
  2. Aug 20, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=< 2.1.13
  2. Affected versionversion=>= 2.2.0-alpha, < 2.2.2-alpha

What conditions does exploitation require?

Attack vectorlocal
Required privilegesunauthenticated

What is affected?

Libevent · Libeventversion=< 2.1.13; version=>= 2.2.0-alpha, < 2.2.2-alpha

Published CVSS scores

8.4GitHubCVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-787Out-of-bounds Write
CWE-617Reachable Assertion

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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