VulnerabilityPublished 13 May 2026

CVE-2026-8463: LEONT Crypt::Argon2 · Buffer Over-read

Affects LEONT Crypt::Argon2Source CVE Database V5

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Not known to be exploited · CVSS 5.3 Medium : upgrade to 0.031 when convenient.

Data as of 10 Nov 2026, 23:24 UTC

CVSS 3.1 base score

5.3Medium

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

EPSS: 0.3% chance of exploitation in 30 days – higher than 26% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in 0.031

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

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

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: None: There is no loss of confidentiality within the impacted component.
Integrity: None: There is no loss of integrity within the impacted component.
Availability: Low: Performance is reduced or there are interruptions in resource availability. Even if repeated exploitation of the vulnerability is possible, the attacker does not have the ability to completely deny service to legitimate users. The resources in the impacted component are either partially available all of the time, or fully available only some of the time, but overall there is no direct, serious consequence to the impacted component.

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 13 May 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 10 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 Crypt::Argon2 and Crypt-Argon2 to 0.031.

Affected software

Product	Affected	Fixed in
LEONTCrypt::Argon2	Affected >=0.017 <0.031	Fixed in 0.031
GitHubCrypt-Argon2`pkg:github/Crypt-Argon2`Other threats	Affected >=0.017 <0.031	Fixed in 0.031

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 invoking argon2_verify with potentially empty encoded input strings. Validate inputs before calling argon2_verify to ensure encoded strings are non-empty to prevent triggering the out-of-bounds read.

Description

CVE-2026-8463 is a medium severity vulnerability in LEONT's Crypt::Argon2 Perl module versions from 0.017 before 0.031. It involves a heap out-of-bounds read in the argon2_verify function when processing an empty encoded input string. This occurs because the function passes encoded_len - 1 to memchr without verifying that encoded_len is non-zero, causing an underflow and resulting in memory beyond the heap being read. This can lead to process crashes or unintended information disclosure related to adjacent memory content.

Impact

The vulnerability can cause a denial of service through process crashes due to out-of-bounds memory reads. Additionally, it may leak information about adjacent heap memory contents, specifically the position of a '$' byte, which could be used in further parsing or analysis. There is no indication of confidentiality, integrity, or availability impacts beyond these effects. No known exploits are reported in the wild.

Summary

The vulnerability in Crypt::Argon2 versions 0.017 up to but not including 0.031 arises from improper handling of empty encoded input in the argon2_verify function. Specifically, the function uses encoded_len - 1 as the length argument to memchr without checking if encoded_len is zero. When the encoded string is empty, this subtraction underflows to SIZE_MAX, causing memchr to scan out-of-bounds heap memory searching for a '$' separator byte. This can cause a heap out-of-bounds read, potentially crashing the process or leaking memory content related to the position of the '$' byte in adjacent memory. The issue is classified under CWE-126 (Buffer Over-read) and CWE-191 (Integer Underflow).

CWE-126Buffer Over-read (opens in a new tab)
Variant weakness
The product reads from a buffer using buffer access mechanisms such as indexes or pointers that reference memory locations after the targeted buffer.
OWASP Cheat Sheets
XML Security (opens in a new tab)
Mass Assignment (opens in a new tab)
OWASP ASVS 4.0.3
V13.3.1 (opens in a new tab)
V5.1.4 (opens in a new tab)
V5.1.3 (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).
CWE-191Integer Underflow (Wrap or Wraparound) (opens in a new tab)
Base weakness
The product subtracts one value from another, such that the result is less than the minimum allowable integer value, which produces a value that is not equal to the correct result.

References

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 20 May 2026, 19:16 UTC

WeaknessesCWE-126, CWE-191

Technical details

References

Community reviews

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