CVE-2025-6704: An arbitrary file writing vulnerability in the Secure PDF eXchange (SPX) feature of Sophos Firewall versions o

Q: How do I fix CVE-2025-6704?

firewall firmware: upgrade to 21.0.2. Exact commands for each OS are on this page.

Q: Is CVE-2025-6704 being exploited?

CVE-2025-6704 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2025-6704 affect?

CVE-2025-6704 affects firewall firmware. Severity is critical (CVSS 9.8). An arbitrary file writing vulnerability in the Secure PDF eXchange (SPX) feature of Sophos Firewall versions older than 21.0 MR2 (21.0.2) can lead to pre-auth remote code execution, if a specific configuration of SPX is enabled in combinati

Q: How urgent is CVE-2025-6704?

Priority 66/100. Critical severity; EPSS top 4%: very likely to be exploited; CISA SSVC: automatable with total technical impact; Remotely exploitable, no login, no user action

This week

CRITICAL 9.8REMOTEUPGRADE

CVE-2025-6704 is a critical-severity flaw (CVSS 9.8) affecting firewall firmware. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

An arbitrary file writing vulnerability in the Secure PDF eXchange (SPX) feature of Sophos Firewall versions older than 21.0 MR2 (21.0.2) can lead to pre-auth remote code execution, if a specific configuration of SPX is enabled in combination with the firewall running in High Availability (HA) mode.

Why this priority

Critical severity
EPSS top 4%: very likely to be exploited
CISA SSVC: automatable with total technical impact
Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	9.8 (Critical)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	11.8% (top 4%)
CISA exploited list	No
Weakness	CWE-78
Published	2025-07-21
Last modified	2026-06-17

Publisher (CNA): Sophos Limited · Vendor: sophos

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

Am I affected?

Timeline

2025-07-21 14:15 UTCPublished CVE record published
2026-06-17 10:02 UTCUpdated Record last modified

sophos firewall firmware UPGRADE

Affected: < 21.0.2

Fixed in: 21.0.2

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.

Exact fixes by distribution

Fedora 46 · opensips · FIXED · 4.0.3-1.fc46 · FEDORA-2026-6700a0026c · source

sudo dnf upgrade --advisory=FEDORA-2026-6700a0026c

Fedora ELN · ibus-typing-booster · FIXED · 2.31.3-1.eln159 · FEDORA-2026-c895c68d60 · source

sudo dnf upgrade --advisory=FEDORA-2026-c895c68d60

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-2025-6704?

firewall firmware: upgrade to 21.0.2. Exact commands for each OS are on this page.

Is CVE-2025-6704 being exploited?

CVE-2025-6704 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-2025-6704 affect?

CVE-2025-6704 affects firewall firmware. Severity is critical (CVSS 9.8). An arbitrary file writing vulnerability in the Secure PDF eXchange (SPX) feature of Sophos Firewall versions older than 21.0 MR2 (21.0.2) can lead to pre-auth remote code execution, if a specific configuration of SPX is enabled in combinati

How urgent is CVE-2025-6704?

Priority 66/100. Critical severity; EPSS top 4%: very likely to be exploited; CISA SSVC: automatable with total technical impact; Remotely exploitable, no login, no user action

Software pages

Sophos vulnerabilities

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References

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