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CVE-2026-63384— Libevent: `evtag_unmarshal_header()` decodes a wire `uint32` length into a signed `int` return value.

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 和 2.2.2-alpha 之前，libevent 在 event_tagging.c 中存在一个不正确的整数转换漏洞。当 evtag_unmarshal_header 调用 evtag_decode_int 来解码攻击者控制的 uint32 类型负载长度，并将其作为 signed int 返回时，会出现问题。当值超过 INT_MAX 时，结果会变成负数或被截断。随后，evtag_unmarshal_string 可能会在分配内存大小计算中使用该转换后的值，

CVSS 8.7 · High EPSS 0.38% · P32

Possible ATT&CK Techniques 1 AI

T1496 · Resource Hijacking

Affected Version Matrix 2

VendorProduct Version RangeStatus
libevent libevent >= 2.2.0-alpha, < 2.2.2-alpha affected
< 2.1.13 affected
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I. Basic Information for CVE-2026-63384

Vulnerability Information
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Vulnerability Title
Libevent: `evtag_unmarshal_header()` decodes a wire `uint32` length into a signed `int` return value.
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 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.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
Source: CVE Program / CVE List V5
Vulnerability Type
整数溢出或超界折返
Source: CVE Program / CVE List V5

Affected Products

Vendor Product Affected Versions CPE Subscribe
libevent libevent >= 2.2.0-alpha, < 2.2.2-alpha -

II. Public POCs for CVE-2026-63384

# POC Description Source Link Shenlong Link
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Qwen3.6-35B-A3B · 12598 chars
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III. Intelligence Information for CVE-2026-63384

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Patches & Fixes for CVE-2026-63384 (2)

Vendor Advisories for CVE-2026-63384 (1)

Vendor Pages for CVE-2026-63384 (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-2026-63383 8.7 HIGH Libevent: decode_tag_internal() can lead to out-of-bounds read
CVE-2026-63388 8.4 HIGH Libevent: Heap out-of-bounds write in bufferevent_socket_set_conn_address_ reachable via A
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-190

V. Comments for CVE-2026-63384

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