CVE-2013-1623: The TLS and DTLS implementations in wolfSSL CyaSSL before 2.5.0 do not properly consider timing side-channel a

Q: How do I fix CVE-2013-1623?

cyassl: upgrade to newer than 2.4.6. Exact commands for each OS are on this page.

Q: Is CVE-2013-1623 being exploited?

CVE-2013-1623 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-2013-1623 affect?

CVE-2013-1623 affects cyassl. Severity is medium (CVSS 4.3). The TLS and DTLS implementations in wolfSSL CyaSSL before 2.5.0 do not properly consider timing side-channel attacks on a noncompliant MAC check operation during the processing of malformed CBC padding, which allows remote attackers to cond

Q: How urgent is CVE-2013-1623?

Priority 36/100. No elevated risk signals yet.

Routine

MEDIUM 4.3UPGRADE

CVE-2013-1623 is a medium-severity flaw (CVSS 4.3) affecting cyassl. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

The TLS and DTLS implementations in wolfSSL CyaSSL before 2.5.0 do not properly consider timing side-channel attacks on a noncompliant MAC check operation during the processing of malformed CBC padding, which allows remote attackers to conduct distinguishing attacks and plaintext-recovery attacks via statistical analysis of timing data for crafted packets, a related issue to CVE-2013-0169.

Why this priority

No elevated risk signals yet

A fixed release or distro patch exists.

Risk facts

CVSS score	4.3 (Medium)
EPSS exploit chance	2.4% (top 16%)
CISA exploited list	No
Weakness	CWE-310
Published	2013-02-08
Last modified	2026-06-16

Publisher (CNA): MITRE · Vendor: yassl

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

Am I affected?

Timeline

2013-02-08 19:55 UTCPublished CVE record published
2026-06-16 23:51 UTCUpdated Record last modified

yassl cyassl UPGRADE

Affected: <= 2.4.6 · 0.2.0 · 0.3.0 · 0.4.0 · 0.5.0 · 0.5.5 · 0.6.0 · 0.6.2

Fixed in: newer than 2.4.6

Safe to downgrade to: no unaffected older release

1. Check installed version

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

2. UPGRADE to newer than 2.4.6 (Debian / Ubuntu)

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

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade cyassl

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-2013-1623?

cyassl: upgrade to newer than 2.4.6. Exact commands for each OS are on this page.

Is CVE-2013-1623 being exploited?

CVE-2013-1623 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-2013-1623 affect?

CVE-2013-1623 affects cyassl. Severity is medium (CVSS 4.3). The TLS and DTLS implementations in wolfSSL CyaSSL before 2.5.0 do not properly consider timing side-channel attacks on a noncompliant MAC check operation during the processing of malformed CBC padding, which allows remote attackers to cond

How urgent is CVE-2013-1623?

Priority 36/100. No elevated risk signals yet.

Software pages

wolfSSL vulnerabilities

Related CVEs

CVE-2014-2900 MEDIUM 5.8 UPGRADE wolfSSL CyaSSL before 2.9.4 does not properly validate X.509 certificates with unknown critical extensions, wh
CVE-2014-2899 MEDIUM 5.0 UPGRADE wolfSSL CyaSSL before 2.9.4 allows remote attackers to cause a denial of service (NULL pointer dereference) vi

References

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