CVE-2026-57053Public exploit

IDN result corruption via unchecked prefix offset

Published Jun 23, 2026 · Updated Jun 23, 2026

Out-of-bounds reads in GNU Libidn before 1.44 allow local users to alter IDN conversion results via crafted Punycode labels. In idna_to_unicode_internal, round-trip verification skips four bytes of a re-encoded label without confirming that the xn-- prefix is present. Exploitation depends on stack layout and an application passing attacker-controlled labels to a ToUnicode API; outcomes include invalid-label acceptance or a process crash.

CVSS severity4.0
Medium
EPSS probability0.15%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Out-of-bounds reads in GNU Libidn before 1.44 allow local users to alter IDN conversion results via crafted Punycode labels. In idna_to_unicode_internal, round-trip verification skips four bytes of a re-encoded label without confirming that the xn-- prefix is present. Exploitation depends on stack layout and an application passing attacker-controlled labels to a ToUnicode API; outcomes include invalid-label acceptance or a process crash.

The record

CVE
CVE-2026-57053
Published
Jun 23, 2026
Updated
Jun 23, 2026
Vendor
The GnuPG Project
Product
Libidn
Classifications
CWE-1284, T1499
Attack vector
local
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jun 23, 2026CVE publishedPublication date reported by the CVE source.
  2. Jun 23, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=0 <1.44

What conditions does exploitation require?

Attack vectorlocal
Required privilegesunauthenticated

What is affected?

The GnuPG Project · Libidnversion=0 <1.44

Published CVSS scores

2.5NIST NVDCVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:L/A:N
4.0MITRECVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:L
5.3Amazon LinuxCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-1284Improper Validation of Specified Quantity in Input
T1499Endpoint Denial of Service

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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