CVE-2026-81721: openssl_encrypt before 1.4.9 fails to validate KDF cost parameters in encrypted file metadata and keystore hea

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HIGH 7.5REMOTEWATCHLISTUPGRADE

CVE-2026-81721 is a high-severity flaw (CVSS 7.5) affecting openssl encrypt. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

openssl_encrypt before 1.4.9 fails to validate KDF cost parameters in encrypted file metadata and keystore headers, allowing attackers to trigger unbounded memory allocation. Attackers can craft malicious encrypted files declaring arbitrarily large Argon2, scrypt, or balloon KDF parameters to exhaust system memory and crash the process without authentication.

Why this priority

High severity
Remotely exploitable, no login, no user action
On your watchlist

A fixed release or distro patch exists.

Risk facts

CVSS score	7.5 (High)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	0.6% (top 53%)
CISA exploited list	No
Weakness	CWE-400
Published	2026-08-27
Last modified	2026-09-02

Publisher (CNA): VulnCheck · Vendor: jahlives

Last updated 2026-09-02 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-08-27 17:21 UTCPublished CVE record published
2026-09-02 13:15 UTCUpdated Record last modified

jahlives openssl encrypt UPGRADE

Affected: < 1.4.9

Fixed in: 1.4.9

Safe to downgrade to: no unaffected older release

1. Check installed version

pip show openssl-encrypt

2. UPGRADE to 1.4.9

pip install --upgrade "openssl-encrypt>=1.4.9"

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-2026-81721?

openssl encrypt: upgrade to 1.4.9. Exact commands for each OS are on this page.

Is CVE-2026-81721 being exploited?

CVE-2026-81721 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-2026-81721 affect?

CVE-2026-81721 affects openssl encrypt. Severity is high (CVSS 7.5). openssl_encrypt before 1.4.9 fails to validate KDF cost parameters in encrypted file metadata and keystore headers, allowing attackers to trigger unbounded memory allocation. Attackers can craft malicious encrypted files declaring arbitrari

How urgent is CVE-2026-81721?

Priority 48/100. High severity; Remotely exploitable, no login, no user action; On your watchlist

Software pages

OpenSSL vulnerabilities

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References

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