No exploitation reportedFix available

CVE-2018-15836

Q: Is CVE-2018-15836 actively exploited?

Active exploitation of CVE-2018-15836 has not been confirmed. Its EPSS score was 1.5% on 2026-10-23, the estimated probability of exploitation in the next 30 days.

Q: What is the CVSS score for CVE-2018-15836?

CVE-2018-15836 has a CVSS v3 base score of 7.5 (HIGH severity), with vector string CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N.

No exploitation reported by the sources we read.

Published2018-09-26
Fixed in2.6.50.1
WeaknessCWE-347

Am I affected?

With a domain, we read the version its public headers and pages expose. A distribution build can carry the fix under an older number.

Description

In verify_signed_hash() in lib/liboswkeys/signatures.c in Openswan before 2.6.50.1, the RSA implementation does not verify the value of padding string during PKCS#1 v1.5 signature verification. Consequently, a remote attacker can forge signatures when small public exponents are being used. IKEv2 signature verification is affected when RAW RSA keys are used.

Timeline

dates in UTC

2018-09-2621:29CVE publishedNVD

Observed activity

isMalicious corpus · updated 2026-10-23 21:37 UTC

Indicators tagged with this CVE, per day0 indicators over 7 days

Block these indicators

Firewall list (EDL, text): https://api.ismalicious.com/edl/cve/CVE-2018-15836?format=txt
CSV export: https://api.ismalicious.com/edl/cve/CVE-2018-15836?format=csv
TAXII collection of exploited CVEs
The EDL and CSV take an API key on the Pro plan.

Versions per branch

NVD

Xelerance openswan

Branch	Affected	Fixed in	Source
2.6	< 2.6.50.1	2.6.50.1	NVD

as publishedRanges as NVD and OSV publish them; a distribution’s build can be fixed under an older number.

Fix

Update Xelerance openswan to 2.6.50.1

Advisories and patches

github.comPatch · Vendor Advisory
github.comPatch · Vendor Advisory
lists.openswan.orgRelease Notes · Vendor Advisory

Detection

Nuclei template: none so far
Exploit-DB: no entry
Proof-of-concept repositories: none listed

Sources

NVDCVSS 3.07.5read 2026-10-23
NVDCVSS 2.05read 2026-10-23
NVDweakness (CWE)CWE-347read 2026-10-23
FIRST EPSSEPSS score1.5 %2026-10-23

Technical details

CVSS v3 Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
Published: 2018-09-26
Last Modified: 2026-06-17
NVD status: Modified

Frequently asked questions

What is CVE-2018-15836?

Is CVE-2018-15836 actively exploited?

Active exploitation of CVE-2018-15836 has not been confirmed. Its EPSS score was 1.5% on 2026-10-23, the estimated probability of exploitation in the next 30 days.

What is the CVSS score for CVE-2018-15836?

CVE-2018-15836 has a CVSS v3 base score of 7.5 (HIGH severity), with vector string CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N.

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