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CVE-2018-0500: Curl_smtp_escape_eob in lib/smtp.c in curl 7.54.1 to and including curl 7.60.0 has a heap-based buffer overflo

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CRITICAL 9.8REMOTEWATCHLISTUPGRADEMITIGATE

CVE-2018-0500 is a critical-severity flaw (CVSS 9.8) affecting curl, ubuntu linux. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Curl_smtp_escape_eob in lib/smtp.c in curl 7.54.1 to and including curl 7.60.0 has a heap-based buffer overflow that might be exploitable by an attacker who can control the data that curl transmits over SMTP with certain settings (i.e., use of a nonstandard --limit-rate argument or CURLOPT_BUFFERSIZE value).

Why this priority

  • Critical severity
  • EPSS top 6%: very likely to be exploited
  • Public exploit reference
  • Remotely exploitable, no login, no user action
  • On your watchlist

A fixed release or distro patch exists.

Risk facts

CVSS score9.8 (Critical)
Attack vectorNetwork (remote)
Attack complexityLow
Privileges neededNone
User interactionNone
EPSS exploit chance6.4% (top 6%)
CISA exploited listNo
WeaknessCWE-787
Published2018-07-11
Last modified2026-06-17
Publisher (CNA): Debian GNU/Linux · Vendor: canonical · haxx

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

Am I affected?

Timeline

haxx curl UPGRADE
Affected: >= 7.54.1 and <= 7.60.0
Fixed in: newer than 7.60.0
Safe to downgrade to: a release before 7.54.1
1. Check installed version
apt-cache policy curl || rpm -q curl || curl --version
2. UPGRADE to newer than 7.60.0 (Debian / Ubuntu)
sudo apt update && sudo apt install --only-upgrade curl
2. UPGRADE (RHEL / Amazon Linux / Fedora)
sudo dnf upgrade curl
Note
Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.
3. If no update is available yet, DOWNGRADE to a release before 7.54.1 (Debian / Ubuntu)
apt-cache madison curl sudo apt install curl=<VERSION_BEFORE_7.54.1> sudo apt-mark hold curl
3. If no update is available yet, DOWNGRADE (RHEL / Amazon Linux / Fedora)
dnf --showduplicates list curl sudo dnf downgrade curl-<VERSION_BEFORE_7.54.1> sudo dnf versionlock add curl
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.
canonical ubuntu linux MITIGATE
Affected: 17.10 · 18.04
Fixed in: no fixed release known
Safe to downgrade to: a release before 17.10
Check your OS release
cat /etc/os-release; uname -r
Debian / Ubuntu
sudo apt update && sudo apt full-upgrade
RHEL / Amazon Linux / Fedora
sudo dnf upgrade --refresh
Windows
Install the latest cumulative update from Windows Update
If no patch exists yet
OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.

Exact fixes by distribution

A distro patch exists: prefer upgrading over downgrading.
Fedora 46 · root · FIXED · 6.40.04-6.fc46 · FEDORA-2026-deac340022 · source
sudo dnf upgrade --advisory=FEDORA-2026-deac340022
Fedora ELN · man-pages · FIXED · 6.20-1.eln159 · FEDORA-2026-f1f5fb11b4 · source
sudo dnf upgrade --advisory=FEDORA-2026-f1f5fb11b4
Debian 12 · curl · FIXED · 7.61.0-1
sudo apt update && sudo apt install --only-upgrade curl dpkg --compare-versions "$(dpkg-query -W -f='${Version}' curl)" ge "7.61.0-1" && echo PATCHED || echo STILL-VULNERABLE
Debian 13 · curl · FIXED · 7.61.0-1
sudo apt update && sudo apt install --only-upgrade curl dpkg --compare-versions "$(dpkg-query -W -f='${Version}' curl)" ge "7.61.0-1" && echo PATCHED || echo STILL-VULNERABLE
RHEL 5 · curl · NOT AFFECTED
RHEL 6 · curl · NOT AFFECTED
RHEL 7 · curl · NOT AFFECTED
RHEL 8 · curl · NOT AFFECTED
Alpine 3.20 · curl · FIXED · curl-7.61.0-r0
apk add --upgrade curl apk info -v curl
Alpine 3.21 · curl · FIXED · curl-7.61.0-r0
apk add --upgrade curl apk info -v curl
Alpine 3.22 · curl · FIXED · curl-7.61.0-r0
apk add --upgrade curl apk info -v curl
Alpine 3.23 · curl · FIXED · curl-7.61.0-r0
apk add --upgrade curl apk info -v curl
Amazon Linux 2 · see advisory · FIXED · ALAS2-2018-1052 · source
sudo yum update --advisory=ALAS2-2018-1052
Amazon Linux 1 · see advisory · FIXED · ALAS-2019-1151 · source
sudo yum update --advisory=ALAS-2019-1151
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-2018-0500?

curl: upgrade to newer than 7.60.0; ubuntu linux: mitigate or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2018-0500 being exploited?

CVE-2018-0500 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-2018-0500 affect?

CVE-2018-0500 affects curl, ubuntu linux. Severity is critical (CVSS 9.8). Curl_smtp_escape_eob in lib/smtp.c in curl 7.54.1 to and including curl 7.60.0 has a heap-based buffer overflow that might be exploitable by an attacker who can control the data that curl transmits over SMTP with certain settings (i.e., use

How urgent is CVE-2018-0500?

Priority 73/100. Critical severity; EPSS top 6%: very likely to be exploited; Public exploit reference; Remotely exploitable, no login, no user action; On your watchlist

Software pages

Ubuntu vulnerabilities · curl vulnerabilities

Related CVEs

References

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