CVE-2021-35296: An issue in the administrator authentication panel of PTCL HG150-Ub v3.0 allows attackers to bypass authentica

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CRITICAL 9.8REMOTEMITIGATE

CVE-2021-35296 is a critical-severity flaw (CVSS 9.8) affecting hg150-ub firmware. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

An issue in the administrator authentication panel of PTCL HG150-Ub v3.0 allows attackers to bypass authentication via modification of the cookie value and Response Path.

Why this priority

Critical 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	9.8 (Critical)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	2.0% (top 19%)
CISA exploited list	No
Weakness	CWE-287
Published	2021-10-04
Last modified	2026-06-17

Publisher (CNA): MITRE · Vendor: ptcl

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

Am I affected?

Timeline

2021-10-04 17:15 UTCPublished CVE record published
2026-06-17 03:57 UTCUpdated Record last modified

ptcl hg150-ub firmware MITIGATE

Affected: 3.0

Fixed in: no fixed release known

Safe to downgrade to: a release before 3.0

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.

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-2021-35296?

hg150-ub firmware: mitigate or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2021-35296 being exploited?

CVE-2021-35296 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-2021-35296 affect?

CVE-2021-35296 affects hg150-ub firmware. Severity is critical (CVSS 9.8). An issue in the administrator authentication panel of PTCL HG150-Ub v3.0 allows attackers to bypass authentication via modification of the cookie value and Response Path.

How urgent is CVE-2021-35296?

Priority 64/100. Critical severity; Public exploit reference; Remotely exploitable, no login, no user action

Related CVEs

CVE-2022-36200 HIGH 7.5 MITIGATE In FiberHome VDSL2 Modem HG150-Ub_V3.0, Credentials of Admin are submitted in URL, which can be logged/sniffed
CVE-2021-41946 MEDIUM 5.4 MITIGATE In FiberHome VDSL2 Modem HG150-Ub_V3.0, a stored cross-site scripting (XSS) vulnerability in Parental Control

References

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