Apache-AppSamurai: Predictable from Observable State (CVE-2026-19565)
Published Last modified Sources: CVE.org
What is affected, what to do
Apache::AppSamurai::Util versions through 1.01 for Perl generate predictable session authentication keys from the clock and process id in CreateSessionAuthKey. CreateSessionAuthKey runs five rounds of SHA-256, each over a fresh Time::HiRes reading formatted to six decimal places, the running digest, and the process id.
The available sources name no fixed version. Check the vendor guidance in the references below.
- Affected
- Apache-AppSamurai
lte *..1.01
- Apache-AppSamurai
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Metrics
3.7
Priority
XIEM Effective CVSS: highest available CVSS rating from NVD and vendor data.
Source: Vendor (CNA), CVSS v3
3.7
CVSS v3
Severity Low on the scale from 0 to 10.
Source: CVE.org
0.4 %
EPSS score
Low — model estimates < 1% exploitation likelihood.
Source: FIRST EPSS, percentile 34.2
Show all metrics
- Severity
- Low
Priority (0–325)
The priority score is a consolidated metric that condenses several individual signals into a single, action-guiding ranking: technical severity (CVSS), exploitation likelihood (EPSS), known-exploited status (KEV) and the context of the affected asset. The aim is to answer the only truly important question in vulnerability management: what first?
Read in glossary- 52.85 Methodology
Exploit maturity
An exploit is code or a technique that specifically uses a concrete vulnerability to force unintended behaviour — such as executing code or escalating privileges. It is the tool that turns a theoretical flaw into a practical attack.
Read in glossary- no public PoC known
XIEM Effective CVSS
XIEM® is the tiered managed-security operating model from NEOSEC and a registered trademark of NEOSEC GmbH. It extends classic SIEM — the central collection, normalisation and correlation of security-relevant events — with endpoint forensics, network visibility and deception technology, and consolidates them into three building tiers: Sentry, Orchestrate and Command.
Read in glossary- 3.7 Methodology
CVSS v3
CVSS is the globally established, open standard for assessing the technical severity of a vulnerability on a scale from 0 to 10. It describes how easily a flaw can be exploited and what damage it can cause — but not how likely its actual exploitation is. CVSS and the complementary EPSS deliberately answer different questions.
Read in glossary- 3.7
EPSS score
The EPSS score is the absolute model output for an individual vulnerability: the estimated probability of real-world exploitation within the next 30 days, expressed as a value between 0 and 1 (i.e. 0 % to 100 %). A score of 0.42 means „the model estimates a 42 % chance of real-world exploitation within 30 days“.
Read in glossary- 0.4 %
- Low — model estimates < 1% exploitation likelihood.
EPSS percentile
The EPSS percentile is the relative position of a vulnerability within all EPSS-scored CVEs, expressed as a value between 0 and 1. A percentile of 0.90 means „this CVE has a higher EPSS score than 90 % of all other scored CVEs“. Unlike the EPSS score, it is not a probability — but a positioning within a ranking.
Read in glossary- 34.2
- Elevated — this CVE ranks above at least 10% of all CVEs scored today.
KEV status
The KEV catalogue is a list maintained by the US authority CISA of vulnerabilities for which active exploitation in the wild has been confirmed. It answers not the question „how severe?“ but „is it already being attacked?“ — thereby sharply prioritising patching.
Read in glossary- —
- Published
CWE
CWE is a catalogue of typical weakness types in software and hardware — such as flawed input validation, unsafe memory handling or poor authentication. Where a CVE names a concrete vulnerability in a concrete product, a CWE describes the underlying class of defect.
Read in glossary- CWE-341
Detection rules
No NEOSEC detection rule is available for this vulnerability yet.
Classification under NIS2 and CRA
Rule-based classification from exploitation status and severity. It does not replace a case-by-case assessment.
NIS2
NIS2 is EU Directive (EU) 2022/2555 to raise the level of cybersecurity across the Union. It substantially broadens obligations compared with the first NIS directive: more sectors, mandatory risk management, staged reporting duties and personal accountability of senior management.
Read in glossary- Handle the vulnerability in regular vulnerability handling under Art. 21(2)(e) NIS2.
CRA
The CRA is EU Regulation (EU) 2024/2847 setting horizontal cybersecurity requirements for „products with digital elements“ — from industrial controllers and software to connected consumer devices. For the first time manufacturers must ensure security across the entire product lifecycle, handle vulnerabilities and provide security updates.
Read in glossary- From 11.12.2027, Annex I Part II CRA requires manufacturers of affected products with digital elements to handle vulnerabilities without delay and provide security updates.
ISO/IEC 27001
ISO/IEC 27001 is the internationally leading standard for an information security management system (ISMS). It describes a risk-based, process-oriented framework to systematically plan, implement, review and improve information security.
Read in glossary- Control A.8.8, management of technical vulnerabilities: assess relevance to your systems, plan remediation and keep evidence.
Description
Apache::AppSamurai::Util versions through 1.01 for Perl generate predictable session authentication keys from the clock and process id in CreateSessionAuthKey. CreateSessionAuthKey runs five rounds of SHA-256, each over a fresh Time::HiRes reading formatted to six decimal places, the running digest, and the process id. CreateSession calls it with an empty key source on every login, and the optional Keysource directive is the only route to the other branch. The result is 64 hex characters. The microsecond field of the first reading takes one of a million values, the later readings follow it within microseconds, and the process id is drawn from a small range. The key is returned to the browser as the session cookie, and is combined with the configured server key to compute the session id and to encrypt the stored session data. An attacker who knows the second in which a session was created and the process id of the worker that created it can enumerate candidate keys and recover the victim's cookie, bypassing authentication for the protected resources. Each candidate has to be tried against the server, which validates the cookie with a key the attacker does not hold.
Source: NVD (NIST), cvelistv5
Affected products
The following versions are affected. Older releases of the same product line are also vulnerable unless stated otherwise.
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| — | Apache-AppSamurai |
|
|
Weakness classes (CWE)
CWE-341Predictable from Observable State
Base
A number or object is predictable based on observations that the attacker can make about the state of the system or network, such as time, process ID, etc.
Entry at MITRE CWE-341
References & sources
- metacpan.orgrelease/PAULDOOM/Apache-AppSamurai-1.01/source/lib/Apache/AppSa…related
- metacpan.orgrelease/PAULDOOM/Apache-AppSamurai-1.01/source/lib/Apache/AppSa…related
- openwall.comlists/oss-security/2026/08/23/4
Reanalysis & status changes
Chronological NVD audit events for this CVE — reanalyses, CVSS updates, CPE diffs.
CVE Translatednvd@nist.gov
- Translation: after Title: Apache::AppSamurai::Util versions through 1.01 for Perl generate predictable session authentication keys from the clock and process id in CreateSessionAuthKey, Description: Las versiones de Apache::AppSamurai::Util hasta la 1.01 para Perl generan claves de autenticación de sesión predecibles a partir del reloj y el ID de proceso en CreateSessionAuthKey. CreateSessionAuthKey ejecuta cinco rondas de SHA-256, cada una sobre una lectura nueva de Time::HiRes formateada a seis decimales, el resumen en ejecución y el ID de proceso. CreateSession lo llama con una fuente de clave vacía en cada inicio de sesión, y la directiva opcional Keysource es la única ruta a la otra rama. El resultado son 64 caracteres hexadecimales. El campo de microsegundos de la primera lectura toma uno de un millón de valores, las lecturas posteriores lo siguen en microsegundos, y el ID de proceso se extrae de un rango pequeño. La clave se devuelve al navegador como la cookie de sesión, y se combina con la clave de servidor configurada para calcular el ID de sesión y para cifrar los datos de sesión almacenados. Un atacante que conoce el segundo en que se creó una sesión y el ID de proceso del trabajador que la creó puede enumerar claves candidatas y recuperar la cookie de la víctima, eludiendo la autenticación para los recursos protegidos. Cada candidato debe ser probado contra el servidor, que valida la cookie con una clave que el atacante no posee.
CVE Modifiedaf854a3a-2127-422b-91ae-364da2661108
- Reference: after http://www.openwall.com/lists/oss-security/2026/08/23/4
New CVE Received9b29abf9-4ab0-4765-b253-1875cd9b441e
- Affected: after …
- Description: after Apache::AppSamurai::Util versions through 1.01 for Perl generate predictable session authentication keys from the clock and process id in CreateSessionAuthKey. CreateSessionAuthKey runs five rounds of SHA-256, each over a fresh Time::HiRes reading formatted to six decimal places, the running digest, and the process id. CreateSession calls it with an empty key source on every login, and the optional Keysource directive is the only route to the other branch. The result is 64 hex characters. The microsecond field of the first reading takes one of a million values, the later readings follow it within microseconds, and the process id is drawn from a small range. The key is returned to the browser as the session cookie, and is combined with the configured server key to compute the session id and to encrypt the stored session data. An attacker who knows the second in which a session was created and the process id of the worker that created it can enumerate candidate keys and recover the victim's cookie, bypassing authentication for the protected resources. Each candidate has to be tried against the server, which validates the cookie with a key the attacker does not hold.
- CWE: after CWE-341
- Reference: after https://metacpan.org/release/PAULDOOM/Apache-AppSamurai-1.01/source/lib/Apache/AppSamurai.pm#L1446-1533
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<a href="https://intel.neosec.eu/en/cve/CVE-2026-19565"><img src="https://intel.neosec.eu/badge/cve/CVE-2026-19565.svg?lang=en" alt="CVE-2026-19565 – NEOSEC Intel" height="20"></a>