CVE-2025-40909
MEDIUMDescription
Perl threads have a working directory race condition where file operations may target unintended paths. If a directory handle is open at thread creation, the process-wide current working directory is temporarily changed in order to clone that handle for the new thread, which is visible from any third (or more) thread already running. This may lead to unintended operations such as loading code or accessing files from unexpected locations, which a local attacker may be able to exploit. The bug was introduced in commit 11a11ecf4bea72b17d250cfb43c897be1341861e and released in Perl version 5.13.6
How to fix
This vulnerability affects an unusually large number of packages. The highest-confidence fixes are shown above; the full list is longer. Check the referenced advisories for complete coverage.
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Remediation is compiled from vendor and distribution security advisories. Always confirm against the linked source for your exact version and platform.
CVSS v3 Vector
Exploitability
Impact
CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L
Exploit Intelligence
Moderate risk: more likely to be exploited than 42% of all known CVEs.
References
Related Vulnerabilities
Other CWE-426 vulnerabilities, ordered by exploit likelihood. View all
| CVE | Severity | CVSS | EPSS | Exploited | Fix |
|---|---|---|---|---|---|
| CVE-2015-0096 | High | 9.3 | 71% | - | - |
| CVE-2016-10009 | High | 7.3 | 37% | - | Fix |
| CVE-2016-0016 | High | 7.8 | 30% | - | - |
| CVE-2012-1854 | High | 7.8 | 21% | KEV | - |
| CVE-2018-12589 | High | 7.8 | 20% | - | - |
| CVE-2022-22047 | High | 7.8 | 19% | KEV | Fix |
Common questions
How do I fix CVE-2025-40909?
Published advisories record a fix for 444 affected products. The "How to fix" section on this page lists the fixed version and source advisory for each one, so apply the entry matching what you actually run.
Is CVE-2025-40909 being actively exploited?
Not that we know of. CVE-2025-40909 is not in the CISA Known Exploited Vulnerabilities catalog. Its EPSS score of 0.50% is the estimated probability that it will be exploited in the next 30 days. That is higher than 42% of all scored CVEs.
How severe is CVE-2025-40909?
CVE-2025-40909 has a CVSS v3 base score of 5.9, rated medium. CVSS rates the technical impact if the vulnerability is exploited, not how likely that is, so weigh it alongside the exploit-prediction score when you decide what to patch first.
What does CVE-2025-40909 affect?
Published advisories record a fix for perl (Amazon), perl-Attribute-Handlers (Amazon), perl-AutoLoader (Amazon), perl-AutoSplit (Amazon), and 440 more. The list on this page is capped, so there may be more.
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Markdown
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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2026-06-17.