CVE-2006-3251: Heap-based buffer overflow in the array_push function in hashcash.c for Hashcash before 1.21 might allow attac

Q: How do I fix CVE-2006-3251?

hashcash: upgrade to newer than 1.20. Exact commands for each OS are on this page.

Q: Is CVE-2006-3251 being exploited?

CVE-2006-3251 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2006-3251 affect?

CVE-2006-3251 affects hashcash. Severity is high (CVSS 7.5). Heap-based buffer overflow in the array_push function in hashcash.c for Hashcash before 1.21 might allow attackers to execute arbitrary code via crafted entries.

This month

HIGH 7.5UPGRADE

CVE-2006-3251 is a high-severity flaw (CVSS 7.5) affecting hashcash. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Heap-based buffer overflow in the array_push function in hashcash.c for Hashcash before 1.21 might allow attackers to execute arbitrary code via crafted entries.

Why this priority

High severity

A fixed release or distro patch exists.

Risk facts

CVSS score	7.5 (High)
EPSS exploit chance	3.7% (top 10%)
CISA exploited list	No
Weakness	CWE-119
Published	2006-06-27
Last modified	2026-06-16

Publisher (CNA): MITRE · Vendor: hashcash

Last updated 2026-06-16 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2006-06-27 18:05 UTCPublished CVE record published
2026-06-16 22:26 UTCUpdated Record last modified

hashcash hashcash UPGRADE

Affected: <= 1.20 · 1.00 · 1.01 · 1.02 · 1.03 · 1.04 · 1.05 · 1.06

Fixed in: newer than 1.20

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy hashcash || rpm -q hashcash || hashcash --version

2. UPGRADE to newer than 1.20 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade hashcash

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade hashcash

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2006-3251?

hashcash: upgrade to newer than 1.20. Exact commands for each OS are on this page.

Is CVE-2006-3251 being exploited?

CVE-2006-3251 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2006-3251 affect?

CVE-2006-3251 affects hashcash. Severity is high (CVSS 7.5). Heap-based buffer overflow in the array_push function in hashcash.c for Hashcash before 1.21 might allow attackers to execute arbitrary code via crafted entries.

How urgent is CVE-2006-3251?

Priority 49/100. High severity

Related CVEs

CVE-2012-4469 LOW 2.6 DOWNGRADE Cross-site scripting (XSS) vulnerability in the Hashcash module 6.x-2.x before 6.x-2.6 and 7.x-2.x before 7.x-
CVE-2006-3750 MEDIUM 6.8 DOWNGRADE PHP remote file inclusion vulnerability in server.php in the Hashcash Component (com_hashcash) 1.2.1 for Jooml
CVE-2005-0687 HIGH 7.5 DOWNGRADE Format string vulnerability in Hashcash 1.16 allows remote attackers to cause a denial of service (memory cons

References

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