CVE-2025-13151: Stack-based buffer overflow in libtasn1 version: v4.20.0

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HIGH 7.5REMOTEDOWNGRADE

CVE-2025-13151 is a high-severity flaw (CVSS 7.5) affecting libtasn1. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Stack-based buffer overflow in libtasn1 version: v4.20.0. The function fails to validate the size of input data resulting in a buffer overflow in asn1_expend_octet_string.

Why this priority

High severity
Remotely exploitable, no login, no user action

No fix is published yet: follow the downgrade or mitigation steps.

Risk facts

CVSS score	7.5 (High)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	1.4% (top 28%)
CISA exploited list	No
Weakness	CWE-787
Published	2026-01-07
Last modified	2026-06-17

Publisher (CNA): CERT/CC · Vendor: gnu

Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-01-07 22:15 UTCPublished CVE record published
2026-06-17 08:33 UTCUpdated Record last modified

gnu libtasn1 DOWNGRADE

Affected: 4.20.0

Fixed in: no fixed release known

Safe to downgrade to: a release before 4.20.0

1. Check installed version

apt-cache policy libtasn1 || rpm -q libtasn1 || libtasn1 --version

2. No fixed release: DOWNGRADE to a release before 4.20.0 (Debian / Ubuntu)

apt-cache madison libtasn1 sudo apt install libtasn1=<VERSION_BEFORE_4.20.0> sudo apt-mark hold libtasn1

2. No fixed release: DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list libtasn1 sudo dnf downgrade libtasn1-<VERSION_BEFORE_4.20.0> sudo dnf versionlock add libtasn1

Downgrade risk

Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.

After downgrade

Restart the service, and keep the package held until a fixed release ships.

Advisories and coverage

Official advisories

AlmaLinux Errata: [ALSA-2026:28253] Low: libtasn1 security update 2026-06-25

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-2025-13151?

libtasn1: downgrade or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2025-13151 being exploited?

CVE-2025-13151 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-2025-13151 affect?

CVE-2025-13151 affects libtasn1. Severity is high (CVSS 7.5). Stack-based buffer overflow in libtasn1 version: v4.20.0. The function fails to validate the size of input data resulting in a buffer overflow in asn1_expend_octet_string.

How urgent is CVE-2025-13151?

Priority 49/100. High severity; Remotely exploitable, no login, no user action

References

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