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CVE-2026-63382— libevent evhttp: Multiple HTTP Parser Bugs Enable Request Smuggling

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Libevent evhttp解析器在处理重复的Transfer-Encoding头、逗号分隔的Transfer-Encoding值和块传输中的裸换行时存在不一致，可能导致未经身份验证的远程攻击者解同步请求边界并走私第二个请求，从而绕过访问控制或污染缓存。

CVSS 9.2 · Critical EPSS 0.78% · P55

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-2026-63382

Vulnerability Information
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Vulnerability Title
libevent evhttp: Multiple HTTP Parser Bugs Enable Request Smuggling
Source: CVE Program / CVE List V5
Vulnerability Description
Libevent is an event notification library. Prior to 2.1.13 and 2.2.2-alpha, the libevent evhttp parser in http.c inconsistently handles duplicate Transfer-Encoding headers, comma-separated Transfer-Encoding values, and bare line feeds in chunked framing. evhttp_find_header can select only the first header, evhttp_check_transfer_encoding_ was absent so the previous whole-string comparison fails to recognize valid lists ending in chunked, and evhttp_handle_chunked_read uses EVBUFFER_EOL_CRLF rather than EVBUFFER_EOL_CRLF_STRICT, accepting bare LF chunk terminators. When libevent is deployed behind a proxy that frames the same request differently, an unauthenticated remote attacker can desynchronize request boundaries and smuggle a second request, potentially bypassing access controls or poisoning caches. 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: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Libevent evhttp解析器在处理重复的Transfer-Encoding头、逗号分隔的Transfer-Encoding值和块传输中的裸换行时存在不一致，可能导致未经身份验证的远程攻击者解同步请求边界并走私第二个请求，从而绕过访问控制或污染缓存。
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-2026-63382

# POC Description Source Link Shenlong Link
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Qwen3.6-35B-A3B · 10946 chars
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III. Intelligence Information for CVE-2026-63382

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Patches & Fixes for CVE-2026-63382 (4)

Vendor Advisories for CVE-2026-63382 (1)

Vendor Pages for CVE-2026-63382 (2)

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

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-2026-63388 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-2026-63382

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