WebDyne Perl Framework Remote Code Execution Vulnerability due to Missing Regex Anchor (CVE-2026-78191)
Executive & SecOps Summary
SECOPS ASSESSMENTPerl-based web applications utilizing WebDyne versions 2.031 through 3.021
Remote attackers can bypass file upload restrictions using double extensions (e.g., .psp.pdf) to execute arbitrary Perl code on the server, leading to full system compromise
Immediately upgrade the WebDyne framework to the patched version 3.022 or higher
Affected Products & Version Scope
Remediation & Live Workaround Commands
PATCH & WORKAROUND1. Official Patch & Version Upgrade Commands
WebDyne has released version 3.022 to resolve this regular expression flaw. Upgrade your WebDyne module using CPAN or cpanm.
# Upgrade WebDyne module via CPAN shell
perl -MCPAN -e 'install ASPEER/WebDyne-3.022'
# Alternatively, use cpanm for a quick installation
cpanm WebDyne2. Temporary Workaround & Hardening Configuration
If an immediate upgrade is not feasible, configure your reverse proxy or web server to block requests containing .psp in the middle of the path, especially within upload directories.
# Nginx configuration: Block any requests containing '.psp' in the upload directory
location ~* ^/uploads/.*\.psp {
deny all;
return 403;
}3. Log Audit & IoC Verification Commands
Use the following commands to check the installed WebDyne version and scan web server access logs for potential exploitation attempts.
# 1. Verify the currently installed WebDyne version
perl -MWebDyne -e 'print $WebDyne::VERSION . "\
"'
# 2. Scan access logs for suspicious double-extension requests containing .psp
grep -Ei '\.psp\.[a-zA-Z0-9]+' /var/log/nginx/access.log /var/log/apache2/access.logBlock Exploits Instantly with Managed Virtual Patching Rules
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Technical Root Cause & Exploitation Mechanics
1. Vulnerability Overview & Root Cause
This vulnerability (CVE-2026-78191) exists in the request-handling logic of WebDyne, a Perl-based web framework. WebDyne determines whether to execute a requested file as a Perl page by matching its filename against the internal regular expression WEBDYNE_PSP_EXT_RE. Because this regular expression lacks an end anchor (such as '$'), any file containing '.psp' anywhere in its name is incorrectly identified and executed as a Perl script.
2. Exploitation Mechanics & Attack Scenario
The vulnerability is highly exploitable in environments where the application's file upload feature only validates the final extension of a file.
- An attacker crafts a malicious file containing Perl web shell code and names it with a double extension, such as
report.psp.pdf. - The application's upload filter permits the upload because it only checks the final extension (
.pdf). - Once uploaded, the attacker requests the file directly via its URL (e.g.,
/uploads/report.psp.pdf). - Due to the missing regex anchor, WebDyne matches the
.pspsubstring in the middle of the filename and executes the embedded Perl code on the server.
3. Infrastructure & Business Impact
With a CVSS score of 9.8, this vulnerability poses a critical threat. Successful exploitation allows unauthenticated remote attackers to execute arbitrary system commands under the privileges of the web server process, potentially leading to data exfiltration, lateral movement, ransomware deployment, and complete infrastructure takeover.
Official Vendor Advisories & References
WebDyne versions from 2.031 before 3.022 for Perl execute files with .psp anywhere in the name as Perl pages. WebDyne decides whether to run a requested file as a page by matching its name against WEBDYNE_PSP_EXT_RE, which has no end anchor. An application that accepts uploads by checking only the final extension lets a remote attacker upload a file such as report.psp.pdf and run its embedded Perl by requesting it.
Frequently Asked SecOps Questions (CVE-2026-78191)
FAQQ1. How critical is CVE-2026-78191 and is it actively exploited in the wild?
CVE-2026-78191 is rated CVSS 9.8 (CRITICAL) with a 30-day EPSS exploitation probability of 0.4%. Organizations running affected versions should prioritize patching based on network exposure.
Q2. Which vendors and products are affected by CVE-2026-78191?
Primary impacted vendors include aspeer across webdyne. Scope summary: WebDyne versions 2.031 before 3.022
Q3. What temporary mitigations or workarounds exist for CVE-2026-78191 before patching?
[Mitigation] Immediately upgrade the WebDyne framework to the patched version 3.022 or higher Follow the CLI remediation commands and interactive SecOps checklist on this page to restrict exposure prior to your maintenance window.
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🔗 Related Advisories in Similar Stack (aspeer)
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