CAPTCHA bypass via predictable rand-generated challenges
Published Jul 17, 2026 · Updated Jul 17, 2026
Weak randomness in GD::SecurityImage 1.75 and earlier allows remote attackers to bypass CAPTCHA checks by predicting challenge text. The GD::SecurityImage::random routine samples characters with Perl's built-in rand to create a six-character default challenge, exposing a predictable and reversible value. Exploitation requires a consuming application to use the generated text for CAPTCHA validation; successful prediction permits unauthenticated automated submissions.
Summary
What happened
Weak randomness in GD::SecurityImage 1.75 and earlier allows remote attackers to bypass CAPTCHA checks by predicting challenge text. The GD::SecurityImage::random routine samples characters with Perl's built-in rand to create a six-character default challenge, exposing a predictable and reversible value. Exploitation requires a consuming application to use the generated text for CAPTCHA validation; successful prediction permits unauthenticated automated submissions.
The record
- CVE
- CVE-2026-13082
- Published
- Jul 17, 2026
- Updated
- Jul 17, 2026
- Vendor
- Burak Gürsoy
- Product
- GD::SecurityImage
- Classifications
- CWE-804, CWE-338
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Jul 17, 2026CVE publishedPublication date reported by the CVE source.
- Jul 17, 2026Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
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- Affected versionversion=0 <=1.75
What conditions does exploitation require?
What is affected?
Published CVSS scores
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Attacks
What attackers are doing with it
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Weakness, pattern, technique
Public exploit references
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Technologies
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Your stack
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