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CVE-2026-63380— Libevent: Null Pointer Dereference in `evws_new_session`

Quick assessment

Affected
libevent libevent
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
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 2.2.2-alpha 版本之前，当 进入错误路径时（即 成功返回，但 失败），libevent 在 中可能解引用无效的列表指针。此时， 检查到一个非空的 ，并无条件地调用 ，尽管该会话从未被插入到 中。本地攻击者若能诱发此类分配失败或锁定失败，即可导致进程崩溃。此问题已在 2.2.2-alpha 版本中得到修复。

CVSS 5.7 · Medium EPSS 0.11% · P2

Affected Version Matrix 1

VendorProduct Version RangeStatus
libevent libevent < 2.2.2-alpha affected
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I. Basic Information for CVE-2026-63380

Vulnerability Information
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Vulnerability Title
Libevent: Null Pointer Dereference in `evws_new_session`
Source: CVE Program / CVE List V5
Vulnerability Description
Libevent is an event notification library. Prior to 2.2.2-alpha, libevent can dereference invalid list pointers in ws.c when evws_new_session enters its error path after evhttp_start_ws_ succeeds but bufferevent_enable_locking_ fails. evws_connection_free sees a non-null http_server and unconditionally calls TAILQ_REMOVE even though the session was never inserted into http_server->ws_sessions. A local caller able to induce this allocation or locking failure can crash the process. This issue is fixed in version 2.2.2-alpha.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:4.0/AV:L/AC:H/AT:P/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
Source: CVE Program / CVE List V5
Vulnerability Type
释放后使用
Source: CVE Program / CVE List V5

Affected Products

Vendor Product Affected Versions CPE Subscribe
libevent libevent < 2.2.2-alpha -

II. Public POCs for CVE-2026-63380

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III. Intelligence Information for CVE-2026-63380

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Patches & Fixes for CVE-2026-63380 (1)

Vendor Advisories for CVE-2026-63380 (1)

Vendor Pages for CVE-2026-63380 (1)

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-2026-63388 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`

IV. Related Vulnerabilities

Same product: libevent
Same vendor: libevent
Same weakness: CWE-416

V. Comments for CVE-2026-63380

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