CVE-2018-1000654: GNU Libtasn1-4.13 libtasn1-4.13 version libtasn1-4.13, libtasn1-4.12 contains a DoS, specifically CPU usage wi

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MEDIUM 5.5DOWNGRADE

CVE-2018-1000654 is a medium-severity flaw (CVSS 5.5) affecting libtasn1. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

GNU Libtasn1-4.13 libtasn1-4.13 version libtasn1-4.13, libtasn1-4.12 contains a DoS, specifically CPU usage will reach 100% when running asn1Paser against the POC due to an issue in _asn1_expand_object_id(p_tree), after a long time, the program will be killed. This attack appears to be exploitable via parsing a crafted file.

Why this priority

Public exploit reference

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

Risk facts

CVSS score	5.5 (Medium)
Attack vector	Local
Attack complexity	Low
Privileges needed	None
User interaction	Required
EPSS exploit chance	2.0% (top 19%)
CISA exploited list	No
Published	2018-08-20
Last modified	2026-06-17

Publisher (CNA): MITRE · Vendor: gnu

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

Am I affected?

Timeline

2018-08-20 19:31 UTCPublished CVE record published
2026-06-17 01:33 UTCUpdated Record last modified

gnu libtasn1 DOWNGRADE

Affected: 4.12 · 4.13

Fixed in: no fixed release known

Safe to downgrade to: a release before 4.12

1. Check installed version

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

2. No fixed release: DOWNGRADE to a release before 4.12 (Debian / Ubuntu)

apt-cache madison libtasn1 sudo apt install libtasn1=<VERSION_BEFORE_4.12> sudo apt-mark hold libtasn1

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

dnf --showduplicates list libtasn1 sudo dnf downgrade libtasn1-<VERSION_BEFORE_4.12> 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.

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-2018-1000654?

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

Is CVE-2018-1000654 being exploited?

CVE-2018-1000654 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-2018-1000654 affect?

CVE-2018-1000654 affects libtasn1. Severity is medium (CVSS 5.5). GNU Libtasn1-4.13 libtasn1-4.13 version libtasn1-4.13, libtasn1-4.12 contains a DoS, specifically CPU usage will reach 100% when running asn1Paser against the POC due to an issue in _asn1_expand_object_id(p_tree), after a long time, the pro

How urgent is CVE-2018-1000654?

Priority 44/100. Public exploit reference

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References

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