CVE-2026-63387

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Source
https://cve.org/CVERecord?id=CVE-2026-63387
Import Source
https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-63387.json
JSON Data
https://api.osv.dev/v1/vulns/CVE-2026-63387
Aliases
  • GHSA-58rx-7448-jw47
Downstream
Published
2026-08-20T17:53:41.863Z
Modified
2026-08-22T09:15:43.192418Z
Severity
  • 7.0 (High) CVSS_V3 - CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:H CVSS Calculator
Summary
Libevent: Off-by-one stack buffer overflow in dnsname_to_labels via crafted DNS server response
Details

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 dnsnametolabels formats a name-bearing DNS record at the end of the 64 KB stack buffer allocated by evdnsserverrequestformatresponse. The final-label check permits j plus labellen plus one to equal buflen, 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.

Database specific 
{
    "cwe_ids": [
        "CWE-121",
        "CWE-193",
        "CWE-787"
    ],
    "cna_assigner": "GitHub_M",
    "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/63xxx/CVE-2026-63387.json"
}
References

Affected packages

Git / github.com/libevent/libevent

Affected ranges

Type
GIT
Repo
https://github.com/libevent/libevent
Events
Introduced
0 Unknown introduced commit / All previous commits are affected
Fixed
df3ecad3a040fd6d4fad4287defe113395de6fd7
Fixed
79ddfb460847999b807cba76d04e73891f29c6ee
Database specific
Show details 
{
    "source": [
        "AFFECTED_FIELD",
        "REFERENCES"
    ],
    "extracted_events": [
        {
            "introduced": "2.2.0-alpha"
        },
        {
            "fixed": "2.2.2-alpha"
        },
        {
            "introduced": "0"
        },
        {
            "fixed": "2.1.13"
        }
    ]
}

Affected versions

release-1.*
release-1.1b
release-2.*
release-2.0.1-alpha
release-2.0.10-stable
release-2.0.3-alpha
release-2.0.4-alpha
release-2.0.5-beta
release-2.0.6-rc
release-2.0.7-rc
release-2.0.8-rc
release-2.0.9-rc
release-2.1.1-alpha
release-2.1.10-stable
release-2.1.11-stable
release-2.1.12-stable
release-2.1.2-alpha
release-2.1.3-alpha
release-2.1.4-alpha
release-2.1.5-beta
release-2.1.6-beta
release-2.1.7-rc
release-2.1.8-stable
release-2.1.9-beta
release-2.2.1-alpha

Database specific

source 
"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-63387.json"
vanir_signatures 
[
    {
        "signature_type": "Function",
        "digest": {
            "function_hash": "159443554126248192493229143747497657830",
            "length": 554.0
        },
        "target": {
            "function": "http_check_transfer_encoding_test",
            "file": "test/regress_http.c"
        },
        "source": "https://github.com/libevent/libevent/commit/df3ecad3a040fd6d4fad4287defe113395de6fd7",
        "signature_version": "v1",
        "id": "CVE-2026-63387-09212634",
        "deprecated": false
    },
    {
        "signature_type": "Line",
        "digest": {
            "threshold": 0.9,
            "line_hashes": [
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                "37564212311334647331345684303177453724",
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            ]
        },
        "target": {
            "file": "test/regress_http.c"
        },
        "source": "https://github.com/libevent/libevent/commit/df3ecad3a040fd6d4fad4287defe113395de6fd7",
        "signature_version": "v1",
        "id": "CVE-2026-63387-923050c6",
        "deprecated": false
    },
    {
        "signature_type": "Line",
        "digest": {
            "threshold": 0.9,
            "line_hashes": [
                "270762094980121927552802584929566056086",
                "37564212311334647331345684303177453724",
                "168570413533780985513641597969239978857"
            ]
        },
        "target": {
            "file": "test/regress_http.c"
        },
        "source": "https://github.com/libevent/libevent/commit/79ddfb460847999b807cba76d04e73891f29c6ee",
        "signature_version": "v1",
        "id": "CVE-2026-63387-979e5bed",
        "deprecated": false
    },
    {
        "signature_type": "Function",
        "digest": {
            "function_hash": "159443554126248192493229143747497657830",
            "length": 554.0
        },
        "target": {
            "function": "http_check_transfer_encoding_test",
            "file": "test/regress_http.c"
        },
        "source": "https://github.com/libevent/libevent/commit/79ddfb460847999b807cba76d04e73891f29c6ee",
        "signature_version": "v1",
        "id": "CVE-2026-63387-ebc5ab94",
        "deprecated": false
    }
]
vanir_signatures_modified 
"2026-08-22T09:15:43Z"