Goal Reached Thanks to every supporter — we hit 100%!

Goal: 1000 CNY · Raised: 1336 CNY

100%
Buy Us a Coffee

CVE-2026-63387— Libevent: Off-by-one stack buffer overflow in dnsname_to_labels via crafted DNS server response

CVSS 7.0 · High EPSS 0.35% · P28

Possible ATT&CK Techniques 1AI

T1203 · Exploitation for Client Execution

Affected Version Matrix 2

VendorProductVersion RangeStatus
libeventlibevent>= 2.2.0-alpha, < 2.2.2-alphaaffected
< 2.1.13affected
Get alerts for future matching vulnerabilitiesLog in to subscribe

I. Basic Information for CVE-2026-63387

Vulnerability Information
Have questions about the vulnerability? See if Shenlong's analysis helps!
View Shenlong Deep Dive ↗

Although we use advanced large model technology, its output may still contain inaccurate or outdated information.Shenlong tries to ensure data accuracy, but please verify and judge based on the actual situation.

Vulnerability Title
Libevent: Off-by-one stack buffer overflow in dnsname_to_labels via crafted DNS server response
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 off-by-one stack buffer overflow in evdns.c when dnsname_to_labels formats a name-bearing DNS record at the end of the 64 KB stack buffer allocated by evdns_server_request_format_response. The final-label check permits j plus label_len plus one to equal buf_len, after which the terminating null byte is written to buf[buf_len]. A crafted DNS server response containing PTR, CNAME, MX, NS, or SOA data can trigger the one-byte out-of-bounds write and crash or corrupt the process. This issue is fixed in versions 2.1.13 and 2.2.2-alpha.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:H
Source: CVE Program / CVE List V5
Vulnerability Type
栈缓冲区溢出
Source: CVE Program / CVE List V5

Affected Products

VendorProductAffected VersionsCPESubscribe
libeventlibevent >= 2.2.0-alpha, < 2.2.2-alpha -

II. Public POCs for CVE-2026-63387

#POC DescriptionSource LinkShenlong Link
AI-Generated POCPremium
Qwen3.6-35B-A3B · 13840 chars
Pro+ exclusive includes:
Vulnerability reproduction recording (real sandbox build + trigger, exclusive)
In-depth vulnerability mechanism
Trigger conditions & impact
Full executable POC code
Exploit chain & mitigation
POC zip download
100+ AI POC generations per month

III. Intelligence Information for CVE-2026-63387

请登录查看更多情报信息。

Vendor Advisories for CVE-2026-63387 (1)

Vendor Pages for CVE-2026-63387 (2)

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

CVE-2026-633829.2 CRITICALlibevent evhttp: Multiple HTTP Parser Bugs Enable Request Smuggling
CVE-2026-633859.2 CRITICALLibevent: HTTP header handling bugs create risk of access control bypass.
CVE-2026-633848.7 HIGHLibevent: `evtag_unmarshal_header()` decodes a wire `uint32` length into a signed `int` re
CVE-2026-633838.7 HIGHLibevent: decode_tag_internal() can lead to out-of-bounds read
CVE-2026-633888.4 HIGHLibevent: Heap out-of-bounds write in bufferevent_socket_set_conn_address_ reachable via A
CVE-2026-634957.5 HIGHLibevent: Unbounded memory accumulation in WebSocket server via fragmented frames
CVE-2026-633796.3 MEDIUMLibevent: HTTP Header smuggling
CVE-2026-633815.8 MEDIUMLibevent: Dangling Pointer in `evbuffer_add_buffer_reference`
CVE-2026-633805.7 MEDIUMLibevent: Null Pointer Dereference in `evws_new_session`

IV. Related Vulnerabilities

Same product: libevent
Same vendor: libevent
Same weakness: CWE-121

V. Comments for CVE-2026-63387

No comments yet

Leave a comment