VulnerabilityPublished 22 Sep 2026

CVE-2026-87078: Net-IDN-Encode (Perl module) · Memory Leak

Affects Net-IDN-Encode (Perl module)Source CVE Database V5

Compare

Not known to be exploited · CVSS 9.1 Critical : upgrade to 2.590 as a priority.

Data as of 5 Nov 2026, 00:01 UTC

CVSS 3.1 base score

9.1Critical

How severe the flaw is on the 0–10 CVSS scale.

EPSS: 0.3% chance of exploitation in 30 days – higher than 33% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in 2.590

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H

Attack Vector: Network
Attack Complexity: Low
Privileges Required: None
User Interaction: None
Scope: Unchanged
Confidentiality: High
Integrity: None
Availability: High

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Network: The vulnerable component is bound to the network stack and the set of possible attackers extends beyond the other options listed, up to and including the entire Internet. Such a vulnerability is often termed 'remotely exploitable' and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers).
Attack Complexity: Low: Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success against the vulnerable component.
Privileges Required: None: The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files to carry out an attack.
User Interaction: None: The vulnerable system can be exploited without any interaction from any user.
Scope: Unchanged: An exploited vulnerability can only affect resources managed by the same security authority. In this case, the vulnerable component and the impacted component are either the same, or both are managed by the same security authority.
Confidentiality: High: There is total loss of confidentiality, resulting in all resources within the impacted component being divulged to the attacker. Alternatively, access to only some restricted information is obtained, but the disclosed information presents a direct, serious impact.
Integrity: None: There is no loss of integrity within the impacted component.
Availability: High: There is total loss of availability, resulting in the attacker being able to fully deny access to resources in the impacted component; this loss is either sustained (while the attacker continues to deliver the attack) or persistent (the condition persists even after the attack has completed). Alternatively, the attacker has the ability to deny some availability, but the loss of availability presents a direct, serious consequence to the impacted component (e.g., the attacker cannot disrupt existing connections, but can prevent new connections; the attacker can repeatedly exploit a vulnerability that, in each instance of a successful attack, leaks a only small amount of memory, but after repeated exploitation causes a service to become completely unavailable).

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 22 Sep 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 5 Nov 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponized: A Metasploit exploit module or Exploit-DB entry exists (Metasploit scanner modules do not count), or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Upgrade Net-IDN-Encode (Perl module) to 2.590.

Affected software

Product	Affected	Fixed in
CPANNet-IDN-Encode`pkg:cpan/Net-IDN-Encode`Other threats	Affected >=2.302 <2.590	Fixed in 2.590

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

If you cannot patch yet, avoid processing untrusted or malformed labels with the vulnerable versions of Net::IDN::Punycode. Consider using alternative implementations or applying input validation to limit label lengths before decoding.

Description

CVE-2026-87078 is a critical memory leak vulnerability in Net::IDN::Punycode Perl module versions from 2.302 up to but not including 2.590. The issue occurs in the XS backend during the decode_punycode function, where output buffers are allocated before input validation and only released on successful decoding. Invalid labels cause the buffers to remain allocated, leading to unbounded memory growth proportional to twice the label length per rejected call. This affects only the XS backend implementation.

Impact

An attacker who supplies invalid labels to the decode_punycode function can cause the affected process to leak memory at a rate proportional to twice the length of each rejected label. This can lead to denial of service through resource exhaustion due to unbounded memory growth. The vulnerability does not impact confidentiality or integrity but has a high impact on availability.

Summary

Net::IDN::Punycode versions >=2.302 and <2.590 for Perl contain a memory leak vulnerability (CWE-401) in the XS backend's decode_punycode function. The XS backend allocates a scalar buffer sized at twice the input length before validating the input label. If the label is invalid, the scalar and its buffer are not released due to the error handling path, causing memory to leak on each rejected label. The vulnerability arises because the 63-byte DNS label length limit is only enforced when converting to ASCII, not when converting to Unicode, allowing unbounded label lengths to cause excessive memory allocation. This can cause the process memory to grow significantly when invalid labels are repeatedly supplied.

CWE-401Missing Release of Memory after Effective Lifetime (opens in a new tab)
Variant weaknessLikelihood of exploit: Medium
The product does not sufficiently track and release allocated memory after it has been used, making the memory unavailable for reallocation and reuse.
Implementation · Libraries or Frameworks
Choose a language or tool that provides automatic memory management, or makes manual memory management less error-prone.
Architecture and Design
Use an abstraction library to abstract away risky APIs. Not a complete solution.
Architecture and Design · Build and Compilation
Consider using the Boehm-Demers-Weiser garbage collector (bdwgc), which can help avoid leaks.
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

References

Community reviews

Loading reviews…

Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 17 Oct 2026, 23:23 UTC

WeaknessesCWE-401

Technical details

References

Community reviews

Related threats