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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 是一个事件通知库。在 2.1.13 和 2.2.2-alpha 版本之前，Libevent 中位于 http.c 的 evhttp 解析器在处理重复的 Transfer-Encoding 头、以逗号分隔的 Transfer-Encoding 值以及分块传输编码中出现的裸换行符（bare line feeds）时行为不一致。evhttp_find_header 函数只能选择第一个头字段；evhttp_check_transfer_encoding_ 函数缺失，导致之前的完整字符串比较无法识别以 “c

CVSS 9.2 · Critical EPSS 0.59% · 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-2026-63382

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

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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