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CVE-2026-63388— Libevent: Heap out-of-bounds write in bufferevent_socket_set_conn_address_ reachable via AF_UNIX accept

Quick assessment

Affected
libevent libevent
Exploitation
Public or AI PoC available; prioritize validation
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Libevent 是一个事件通知库。在版本 2.1.13 之前以及 2.2.2-alpha 版本中，Libevent 存在一个堆越界写漏洞，位于 bufferevent_sock.c 文件中。当函数 将内核提供的 AF_UNIX 对等地址复制到 时，会发生堆越界写。 在启用 NDEBUG 的发布版本中， 长度检查机制被禁用。此时，HTTP 服务端（evhttp）的 accept 路径可能将 返回的 110 字节的 sockaddr 结构体写入仅有 28 字节长度的字段中。 任何未认证的本机对等方若能连接到 AF_U

CVSS 8.4 · High EPSS 0.14% · P4

Possible ATT&CK Techniques 1 AI

T1190 · Exploit Public-Facing Application

Affected Version Matrix 2

VendorProduct Version RangeStatus
libevent libevent < 2.1.13 affected
>= 2.2.0-alpha, < 2.2.2-alpha affected
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I. Basic Information for CVE-2026-63388

Vulnerability Information
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Vulnerability Title
Libevent: Heap out-of-bounds write in bufferevent_socket_set_conn_address_ reachable via AF_UNIX accept
Source: CVE Program / CVE List V5
Vulnerability Description
Libevent is an event notification library. Prior to 2.1.13 and 2.2.2-alpha, libevent has a heap out-of-bounds write in bufferevent_sock.c when bufferevent_socket_set_conn_address_ copies a kernel-supplied AF_UNIX peer address into bufferevent_private.conn_address. Release builds compiled with NDEBUG disable the EVUTIL_ASSERT length guard, and the evhttp accept path can pass a 110-byte sockaddr from accept() into the 28-byte field. An unauthenticated local peer able to connect to an AF_UNIX listener can overwrite the adjacent dns_request pointer and heap data, causing memory corruption with confidentiality, integrity, and availability impact. This issue is fixed in versions 2.1.13 and 2.2.2-alpha.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Source: CVE Program / CVE List V5
Vulnerability Type
可达断言
Source: CVE Program / CVE List V5

Affected Products

Vendor Product Affected Versions CPE Subscribe
libevent libevent < 2.1.13 -

II. Public POCs for CVE-2026-63388

# POC Description Source Link Shenlong Link
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Qwen3.6-35B-A3B · 14566 chars
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III. Intelligence Information for CVE-2026-63388

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Patches & Fixes for CVE-2026-63388 (2)

Vendor Advisories for CVE-2026-63388 (1)

Vendor Pages for CVE-2026-63388 (2)

Same Patch Batch · libevent · 2026-08-20 · 10 CVEs total

CVE-2026-63382 9.2 CRITICAL libevent evhttp: Multiple HTTP Parser Bugs Enable Request Smuggling
CVE-2026-63385 9.2 CRITICAL Libevent: HTTP header handling bugs create risk of access control bypass.
CVE-2026-63384 8.7 HIGH Libevent: `evtag_unmarshal_header()` decodes a wire `uint32` length into a signed `int` re
CVE-2026-63383 8.7 HIGH Libevent: decode_tag_internal() can lead to out-of-bounds read
CVE-2026-63495 7.5 HIGH Libevent: Unbounded memory accumulation in WebSocket server via fragmented frames
CVE-2026-63387 7.0 HIGH Libevent: Off-by-one stack buffer overflow in dnsname_to_labels via crafted DNS server res
CVE-2026-63379 6.3 MEDIUM Libevent: HTTP Header smuggling
CVE-2026-63381 5.8 MEDIUM Libevent: Dangling Pointer in `evbuffer_add_buffer_reference`
CVE-2026-63380 5.7 MEDIUM Libevent: Null Pointer Dereference in `evws_new_session`

IV. Related Vulnerabilities

Same product: libevent
Same vendor: libevent
Same weakness: CWE-617

V. Comments for CVE-2026-63388

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