libmojo-jwt-perl — security advisory
Mojo::JWT versions before 1.02 for Perl verify HMAC signatures with a non-constant-time string comparison. The decode() method compares the supplied signature to the recomputed HMAC with Perl's eq operator, which stops at the first differing byte, so the comparison time varies with the number of matching leading bytes. A caller that decodes attacker supplied tokens leaks the expected signature through this timing variation, which can be aggregated over many requests to recover the signature and forge a token.
- Products
- libmojo-jwt-perl
- Affected versions
- 0.09-1, 1.01-1, 1.02-1
- Fixed versions
- 1.02-1
- CVEs
- CVE-2026-9537
- Confirmed fixed CVEs
- Not specified
- Updated in this feed
- 1 Nov 2026, 09:53 UTC · Revision 2
Source evidence
Mojo::JWT versions before 1.02 for Perl verify HMAC signatures with a non-constant-time string comparison. The decode() method compares the supplied signature to the recomputed HMAC with Perl's eq operator, which stops at the first differing byte, so the comparison time varies with the number of matching leading bytes. A caller that decodes attacker supplied tokens leaks the expected signature through this timing variation, which can be aggregated over many requests to recover the signature and forge a token.
osv:DEBIAN-CVE-2026-9537
libmojo-jwt-perl
Fixed versions: Not specified
libmojo-jwt-perl
Fixed versions: Not specified
libmojo-jwt-perl
Fixed versions: 1.02-1
Complete source record
{
"id": "967fc79daea340019e77e1cffb12fb4cc90f3372b3678f5966a9f3cf8bc8aa58",
"url": "https://osv.dev/vulnerability/DEBIAN-CVE-2026-9537",
"method": "structured",
"payload": {
"kind": "advisory",
"title": "DEBIAN-CVE-2026-9537",
"summary": "Mojo::JWT versions before 1.02 for Perl verify HMAC signatures with a non-constant-time string comparison. The decode() method compares the supplied signature to the recomputed HMAC with Perl's eq operator, which stops at the first differing byte, so the comparison time varies with the number of matching leading bytes. A caller that decodes attacker supplied tokens leaks the expected signature through this timing variation, which can be aggregated over many requests to recover the signature and forge a token.",
"evidence": "osv:DEBIAN-CVE-2026-9537",
"products": [
{
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"value": "libmojo-jwt-perl",
"evidence": "/affected/0/package/name"
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"value": "0.09-1",
"evidence": "/affected/0/versions"
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{
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"evidence": "/affected/0/versions"
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{
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{
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"aliases": [
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"metrics": [
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"type": "CVSS_V3",
"score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N"
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"versions": [
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"ecosystem_specific": {
"urgency": "not yet assigned"
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{
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"package": {
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"purl": "pkg:deb/debian/libmojo-jwt-perl?arch=source&distro=trixie",
"ecosystem": "Debian:13"
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"versions": [
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"database_specific": {
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{
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"package": {
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"purl": "pkg:deb/debian/libmojo-jwt-perl?arch=source&distro=forky",
"ecosystem": "Debian:14"
},
"versions": [
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"database_specific": {
"source": "https://storage.googleapis.com/debian-osv/debian-cve-osv/DEBIAN-CVE-2026-9537.json"
},
"ecosystem_specific": {
"urgency": "not yet assigned"
}
}
],
"modified": "2026-10-25T09:47:33.818694669Z",
"provider": "osv",
"upstream": [
"CVE-2026-9537"
],
"references": [
"https://security-tracker.debian.org/tracker/CVE-2026-9537"
]
},
"related_cves": [
{
"value": "CVE-2026-9537",
"evidence": "/upstream"
}
],
"security_relevant": true,
"severity_evidence": "/severity/0/score"
},
"source_id": "core-osv",
"document_id": 445208,
"published_at": "2026-07-17T16:17:20.417+00:00"
}