CVE-2005-0039: Certain configurations of IPsec, when using Encapsulating Security Payload (ESP) in tunnel mode, integrity pro

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MEDIUM 6.4DOWNGRADE

CVE-2005-0039 is a medium-severity flaw (CVSS 6.4) affecting ipsec. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Certain configurations of IPsec, when using Encapsulating Security Payload (ESP) in tunnel mode, integrity protection at a higher layer, or Authentication Header (AH), allow remote attackers to decrypt IPSec communications by modifying the outer packet in ways that cause plaintext data from the inner packet to be returned in ICMP messages, as demonstrated using bit-flipping attacks and (1) Destination Address Rewriting, (2) a modified header leng

Why this priority

EPSS top 9%: very likely to be exploited

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

Risk facts

CVSS score	6.4 (Medium)
EPSS exploit chance	4.1% (top 9%)
CISA exploited list	No
Published	2005-05-10
Last modified	2026-06-16

Publisher (CNA): MITRE · Vendor: nissc

Last updated 2026-06-16 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2005-05-10 04:00 UTCPublished CVE record published
2026-06-16 22:10 UTCUpdated Record last modified

nissc ipsec DOWNGRADE

Affected: 1.0

Fixed in: no fixed release known

Safe to downgrade to: a release before 1.0

1. Check installed version

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

2. No fixed release: DOWNGRADE to a release before 1.0 (Debian / Ubuntu)

apt-cache madison ipsec sudo apt install ipsec=<VERSION_BEFORE_1.0> sudo apt-mark hold ipsec

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

dnf --showduplicates list ipsec sudo dnf downgrade ipsec-<VERSION_BEFORE_1.0> sudo dnf versionlock add ipsec

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-2005-0039?

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

Is CVE-2005-0039 being exploited?

CVE-2005-0039 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-2005-0039 affect?

CVE-2005-0039 affects ipsec. Severity is medium (CVSS 6.4). Certain configurations of IPsec, when using Encapsulating Security Payload (ESP) in tunnel mode, integrity protection at a higher layer, or Authentication Header (AH), allow remote attackers to decrypt IPSec communications by modifying the

How urgent is CVE-2005-0039?

Priority 45/100. EPSS top 9%: very likely to be exploited

References

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