CVE-2018-20503: Allied Telesis 8100L/8 devices allow XSS via the edit-ipv4_interface.php vlanid or subnet_mask parameter.

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MEDIUM 6.1MITIGATE

CVE-2018-20503 is a medium-severity flaw (CVSS 6.1) affecting 8100l\/8 firmware. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Allied Telesis 8100L/8 devices allow XSS via the edit-ipv4_interface.php vlanid or subnet_mask parameter.

Why this priority

EPSS top 10%: very likely to be exploited
Public exploit reference

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

Risk facts

CVSS score	6.1 (Medium)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	Required
EPSS exploit chance	3.9% (top 10%)
CISA exploited list	No
Weakness	CWE-79
Published	2019-05-07
Last modified	2026-06-17

Publisher (CNA): MITRE · Vendor: alliedtelesis

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

Am I affected?

Timeline

2019-05-07 19:29 UTCPublished CVE record published
2026-06-17 01:52 UTCUpdated Record last modified

alliedtelesis 8100l\/8 firmware MITIGATE

Affected: all versions

Fixed in: no fixed release known

Safe to downgrade to: no unaffected older release

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.

Public exploits and detection

Public code exists for this CVE. Treat unpatched systems as at risk, and only run PoCs in a lab.

Exploit-DB: SirsiDynix e-Library 3.5.x - Cross-Site Scripting

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-2018-20503?

8100l\/8 firmware: mitigate or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2018-20503 being exploited?

CVE-2018-20503 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-2018-20503 affect?

CVE-2018-20503 affects 8100l\/8 firmware. Severity is medium (CVSS 6.1). Allied Telesis 8100L/8 devices allow XSS via the edit-ipv4_interface.php vlanid or subnet_mask parameter.

How urgent is CVE-2018-20503?

Priority 49/100. EPSS top 10%: very likely to be exploited; Public exploit reference

Software pages

PHP vulnerabilities

References

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