CVE catalog
CVE-2026-50721
Libreswan, via the function RSA_authenticate_hash_signature_raw_rsa(), did not correctly verify the length of the authentication hash when the SIG payload of an IKEv1 packet was encoded using PKCS #1
- Severity
- High · CVSS 8.1
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H - Published
- Source
- [NVD] · [CVE record]
- EPSS
- 0.39% · Oct 25, 2026
Libreswan, via the function RSA_authenticate_hash_signature_raw_rsa(), did not correctly verify the length of the authentication hash when the SIG payload of an IKEv1 packet was encoded using PKCS #1 RSA Encryption as per RFC 2313. A remote attacker can use a variation on the Bleichenbacher attack to forge the SIG payload when small public exponents are being used (e.g., e=3), which could lead to impersonation. Additionally, a remote attacker, by encoding a shorter than expected hash in the SIG payload, could trigger an assertion leading to denial-of-service. The daemon aborts and restarts; continued exploitation causes sustained denial of service. Remote code execution is not possible. X.509 certificate verifications of remote IKE peers are not affected.
Vulnerable and fixed packages
Distribution-reported package versions and fixes. These do not depend on matching against the OpenFactory package catalog.
| Distribution | Package | Release | Version | Status |
|---|---|---|---|---|
| Debian | libreswan | sid | 5.2-2.5 | fixed |
| Debian | libreswan | forky | 5.2-2.5 | fixed |
| Debian | libreswan | trixie | 5.2-2.2 | vulnerable |
| Debian | libreswan | bookworm | 4.10-2+deb12u1 | vulnerable |
| Cpe | libreswan | Not reported | Not reported | vulnerable |
| Cpe | libreswan | Not reported | 5.3.1 | fixed |
| Cpe | libreswan | Not reported | 5.3.1 | fixed |
Fixed-version evidence
| Distribution | Package | Type | Release | Fixed version | Urgency | Origin | Bugs |
|---|---|---|---|---|---|---|---|
| Debian | libreswan | source | sid | 5.2-2.5 | not yet assigned | Not reported | [1141390] |
| Debian | libreswan | source | forky | 5.2-2.5 | not yet assigned | Not reported | [1141390] |
| Debian | libreswan | source | trixie | (unfixed) | not yet assigned | Not reported | [1141390] |
| Debian | libreswan | source | bookworm | (unfixed) | not yet assigned | Not reported | [1141390] |
| Cpe | libreswan | cpe | Not reported | 5.3.1 | Not reported | Not reported | Not reported |
| Cpe | libreswan | cpe | Not reported | 5.3.1 | Not reported | NVD-CVE-2026-50721 | Not reported |
Notes
[trixie] libreswan: Minor issue
OpenFactory catalog packages
[Debian 12 (Bookworm)]
- [libreswan]Affected
Details (2)
4.10-2+deb12u1· amd64 · bookwormAffected
nvd · libreswan · debian · bookworm; nvd · libreswan · debian · 12
4.10-2+deb12u1· arm64 · bookwormAffected
nvd · libreswan · debian · bookworm; nvd · libreswan · debian · 12
[Debian 13 (Trixie)]
- [libreswan]Affected
Details (2)
5.2-2.2· amd64 · trixieAffected
nvd · libreswan · debian · 13
5.2-2.2· arm64 · trixieAffected
nvd · libreswan · debian · 13
Observed:
References
- [https://ftp.suse.com/pub/projects/security/csaf/rhsa-2026_46396.json]
- [https://libreswan.org/security/CVE-2026-50721/]
- [https://libreswan.org/security/CVE-2026-50721/CVE-2026-50721.txt]
- [https://libreswan.org/security/CVE-2026-50722/CVE-2026-50722.txt]
- [https://nvd.nist.gov/vuln/detail/CVE-2026-50721]
- [https://osv.dev/vulnerability/DEBIAN-CVE-2026-50721]
- [https://security-tracker.debian.org/tracker/CVE-2026-50721]
- [https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-50721.json]
- [https://wid.cert-bund.de/.well-known/csaf/white/2026/wid-sec-w-2026-3043.json]
- [https://www.rfc-editor.org/rfc/rfc2313]
[CERT-Bund public advisories] · [Debian Security Tracker] · [FIRST EPSS] · [National Vulnerability Database (NVD)] · [OSV Package Vulnerability Database] · [Red Hat security advisories and VEX] · [SUSE security advisories and VEX]