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CVE-2026-63385— Libevent: HTTP header handling bugs create risk of access control bypass.

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libevent组织的一个提供事件通知机制的网络开发库。 Libevent 2.1.13之前版本和2.2.2-alpha之前版本存在输入验证错误漏洞，该漏洞源于http.c文件中的evhttp_decode_uri_internal函数将百分号编码的%00字节解码为NUL字符，导致路径被截断并绕过验证，以及evhttp_header_is_valid_value函数接受包含回车或换行符的头值，可能导致头部注入或访问控制绕过。

CVSS 9.2 · Critical EPSS 0.55% · P45

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-2026-63385

Vulnerability Information
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Vulnerability Title
Libevent: HTTP header handling bugs create risk of access control bypass.
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 two HTTP parsing weaknesses in http.c. evhttp_decode_uri_internal decodes percent-encoded %00 bytes into literal NUL characters, which can cause downstream C string operations to truncate a path and bypass validation performed on a different representation. evhttp_header_is_valid_value also accepts obsolete line folding in header values containing carriage return or line feed characters, allowing a proxy and libevent to interpret headers differently and enabling header injection or access control bypass. The CRLF header acceptance is fixed in versions 2.1.13 and 2.2.2-alpha, but the reviewed patches do not clearly remediate the URI NUL-truncation condition.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:L/SC:L/SI:L/SA:N
Source: CVE Program / CVE List V5
Vulnerability Type
HTTP请求的解释不一致性(HTTP请求私运)
Source: CVE Program / CVE List V5
Vulnerability Title
Libevent 输入验证错误漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Libevent是libevent组织的一个提供事件通知机制的网络开发库。 Libevent 2.1.13之前版本和2.2.2-alpha之前版本存在输入验证错误漏洞，该漏洞源于http.c文件中的evhttp_decode_uri_internal函数将百分号编码的%00字节解码为NUL字符，导致路径被截断并绕过验证，以及evhttp_header_is_valid_value函数接受包含回车或换行符的头值，可能导致头部注入或访问控制绕过。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

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

II. Public POCs for CVE-2026-63385

# POC Description Source Link Shenlong Link
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Qwen3.6-35B-A3B · 9782 chars
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III. Intelligence Information for CVE-2026-63385

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Patches & Fixes for CVE-2026-63385 (2)

Vendor Advisories for CVE-2026-63385 (1)

Vendor Pages for CVE-2026-63385 (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-2026-63384 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-2026-63388 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-444

V. Comments for CVE-2026-63385

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