CVE-2020-23776: A SSRF vulnerability exists in Winmail 6.5 in app.php in the key parameter when HTTPS is on

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HIGH 7.5REMOTEDOWNGRADE

CVE-2020-23776 is a high-severity flaw (CVSS 7.5) affecting winmail. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

A SSRF vulnerability exists in Winmail 6.5 in app.php in the key parameter when HTTPS is on. An attacker can use this vulnerability to cause the server to send a request to a specific URL. An attacker can modify the request header 'HOST' value to cause the server to send the request.

Why this priority

High severity
Public exploit reference
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	0.8% (top 44%)
CISA exploited list	No
Weakness	CWE-918
Published	2021-01-26
Last modified	2026-06-17

Publisher (CNA): MITRE · Vendor: winmail project

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

Am I affected?

Timeline

2021-01-26 22:15 UTCPublished CVE record published
2026-06-17 03:04 UTCUpdated Record last modified

winmail project winmail DOWNGRADE

Affected: 6.5

Fixed in: no fixed release known

Safe to downgrade to: a release before 6.5

1. Check installed version

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

2. No fixed release: DOWNGRADE to a release before 6.5 (Debian / Ubuntu)

apt-cache madison winmail sudo apt install winmail=<VERSION_BEFORE_6.5> sudo apt-mark hold winmail

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

dnf --showduplicates list winmail sudo dnf downgrade winmail-<VERSION_BEFORE_6.5> sudo dnf versionlock add winmail

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-2020-23776?

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

Is CVE-2020-23776 being exploited?

CVE-2020-23776 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-2020-23776 affect?

CVE-2020-23776 affects winmail. Severity is high (CVSS 7.5). A SSRF vulnerability exists in Winmail 6.5 in app.php in the key parameter when HTTPS is on. An attacker can use this vulnerability to cause the server to send a request to a specific URL. An attacker can modify the request header 'HOST' va

How urgent is CVE-2020-23776?

Priority 50/100. High severity; Public exploit reference; Remotely exploitable, no login, no user action

Software pages

PHP vulnerabilities

Related CVEs

CVE-2024-25501 HIGH 8.8 UPGRADE An issue WinMail v.7.1 and v.5.1 and before allows a remote attacker to execute arbitrary code via a crafted s
CVE-2020-23774 MEDIUM 6.1 DOWNGRADE A reflected XSS vulnerability exists in tohtml/convert.php of Winmail 6.5, which can cause JavaScript code to

References

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