Medium
Security advisory
In sig_verify() in x509.c in axTLS version 2.1.3 and before, the PKCS#1 v1.5 signature verification does not properly verify the ASN.1 metadata. Consequently, a remote attacker can forge signatures when small public exponents are being used, which could lead to impersonation through fake X.509 certificates. This is an even more permissive variant of CVE-2006-4790 and CVE-2014-1568.
- Products
- Not specified
- Affected versions
- Not specified
- Fixed versions
- Not specified
- CVEs
- CVE-2018-16253
- Confirmed fixed CVEs
- Not specified
- Updated in this feed
- 31 Oct 2026, 12:27 UTC · Revision 1
Source evidence
In sig_verify() in x509.c in axTLS version 2.1.3 and before, the PKCS#1 v1.5 signature verification does not properly verify the ASN.1 metadata. Consequently, a remote attacker can forge signatures when small public exponents are being used, which could lead to impersonation through fake X.509 certificates. This is an even more permissive variant of CVE-2006-4790 and CVE-2014-1568.
osv:CVE-2018-16253
Complete source record
{
"id": "4c266ecc1b0668b72cf121e1a18ae53739f2877563abeb7d80bda4960a666035",
"url": "https://osv.dev/vulnerability/CVE-2018-16253",
"method": "structured",
"payload": {
"kind": "advisory",
"title": "CVE-2018-16253",
"summary": "In sig_verify() in x509.c in axTLS version 2.1.3 and before, the PKCS#1 v1.5 signature verification does not properly verify the ASN.1 metadata. Consequently, a remote attacker can forge signatures when small public exponents are being used, which could lead to impersonation through fake X.509 certificates. This is an even more permissive variant of CVE-2006-4790 and CVE-2014-1568.",
"evidence": "osv:CVE-2018-16253",
"products": [],
"severity": "medium",
"structured": {
"id": "CVE-2018-16253",
"aliases": [
"CVE-2018-16253"
],
"metrics": [
{
"type": "CVSS_V3",
"score": "CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N"
}
],
"affected": [
{
"ranges": [
{
"repo": "https://github.com/igrr/axtls-8266",
"type": "GIT",
"events": [
{
"introduced": "0"
},
{
"fixed": "5efe2947ab45e81d84b5f707c51d1c64be52f36c"
}
],
"database_specific": {
"extracted_events": [
{
"range": [
{
"fixed": "5efe2947ab45e81d84b5f707c51d1c64be52f36c"
}
],
"source": "REFERENCES_COMMIT"
}
]
}
}
],
"database_specific": {
"source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2018-16253.json",
"vanir_signatures": [
{
"id": "CVE-2018-16253-3090bf7e",
"digest": {
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},
"source": "https://github.com/igrr/axtls-8266/commit/5efe2947ab45e81d84b5f707c51d1c64be52f36c",
"target": {
"file": "ssl/x509.c"
},
"deprecated": false,
"signature_type": "Line",
"signature_version": "v1"
},
{
"id": "CVE-2018-16253-94fc8e4b",
"digest": {
"length": 389,
"function_hash": "74073868604478741200156603912144804076"
},
"source": "https://github.com/igrr/axtls-8266/commit/5efe2947ab45e81d84b5f707c51d1c64be52f36c",
"target": {
"file": "ssl/x509.c",
"function": "get_signature"
},
"deprecated": false,
"signature_type": "Function",
"signature_version": "v1"
},
{
"id": "CVE-2018-16253-c256e85e",
"digest": {
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},
"source": "https://github.com/igrr/axtls-8266/commit/5efe2947ab45e81d84b5f707c51d1c64be52f36c",
"target": {
"file": "ssl/os_port.h"
},
"deprecated": false,
"signature_type": "Line",
"signature_version": "v1"
},
{
"id": "CVE-2018-16253-d6e58869",
"digest": {
"length": 702,
"function_hash": "232285230700911005501498625380349597162"
},
"source": "https://github.com/igrr/axtls-8266/commit/5efe2947ab45e81d84b5f707c51d1c64be52f36c",
"target": {
"file": "ssl/x509.c",
"function": "sig_verify"
},
"deprecated": false,
"signature_type": "Function",
"signature_version": "v1"
},
{
"id": "CVE-2018-16253-ec948ef3",
"digest": {
"length": 2514,
"function_hash": "47102076113973104952396175716829351788"
},
"source": "https://github.com/igrr/axtls-8266/commit/5efe2947ab45e81d84b5f707c51d1c64be52f36c",
"target": {
"file": "ssl/x509.c",
"function": "x509_verify"
},
"deprecated": false,
"signature_type": "Function",
"signature_version": "v1"
}
],
"vanir_signatures_modified": "2026-10-20T13:35:33Z"
}
}
],
"modified": "2026-10-20T13:35:33.186965926Z",
"provider": "osv",
"references": [
"https://github.com/igrr/axtls-8266/commit/5efe2947ab45e81d84b5f707c51d1c64be52f36c",
"https://sourceforge.net/p/axtls/mailman/message/36459928/"
],
"provider_metadata": {
"unresolved_ranges": [
{
"cpes": [
"cpe:2.3:a:axtls_project:axtls:*:*:*:*:*:*:*:*"
],
"vendor_product": "axtls_project:axtls",
"extracted_events": [
{
"range": [
{
"last_affected": "2.1.3"
}
],
"source": "CPE_RANGE"
}
]
},
{
"extracted_events": [
{
"range": [
{
"last_affected": "2.1.3"
}
],
"source": "DESCRIPTION"
}
]
}
]
}
},
"related_cves": [
{
"value": "CVE-2018-16253",
"evidence": "/id"
}
],
"security_relevant": true,
"severity_evidence": "/severity/0/score"
},
"source_id": "core-osv",
"document_id": 387851,
"published_at": "2018-11-07T20:29:00.667+00:00"
}