IKEv2 Denial of Service via RSA-SHA1 (PKCS#1 RSASSA-PKCS1-v1_5) authentication payload
Priority MEDIUM 41CWE-347Published · Updated
Key facts
- Attack vector
- Network
- Privileges required
- None
- User interaction
- None
- Attack complexity
- High
- Impact type
- Security bypass, Denial of service
- Confidentiality · integrity · availability
- High · High · High
- Fix status
- Partial Red Hat: 17 fixed, 3 without a fix
Attack profile from CVSS 3.1 · CNA. Fix status from CNA and Red Hat. Impact type from CWE-347 and CWE-617.
Summary
Libreswan, via the function RSA_authenticate_hash_signature_pkcs1_1_5_rsa(), did not correctly verify the DER encoding of the ASN.1 digest when the IKEv2 AUTH payload was encoded using RSASSA-PKCS1-v1_5 (RFC 8017). A remote attacker can use a variation on the Bleichenbacher attack to forge the AUTH payload when small public exponents are used (e.g., e=3), leading to impersonation. Additionally, a remote attacker, by encoding a shorter than expected hash in the AUTH 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 the remote IKE peer are not affected.
Why it matters now
Exploitation None reported CISA SSVC · not in CISA KEV
EPSS 0.00346 28th percentileScored 2026-11-07
Fix Partial libreswan (The Libreswan Project): 5.3.1Red Hat: 14 advisoriesRed Hat: 17 fixed, 3 without a fix
SSVC decision points
CISA ADP · SSVC 2.0.3
- Exploitation
- None
- Automatable
- Yes
- Technical impact
- Partial
The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.
Affected products
| Vendor | Product | Affected versions | Fixed in | Status | Source |
|---|---|---|---|---|---|
| The Libreswan Project | libreswan | up to 5.3 | 5.3.1 | Patch available | CNA |
- libreswan VendorThe Libreswan Project Affected up to 5.3 Fixed in 5.3.1 Patch available CNA
CPE configurations NVD · 1
| CPE | Versions | Role | Vendor |
|---|---|---|---|
| cpe:2.3:a:libreswan:libreswan:*:*:*:*:*:*:*:* | before 5.3.1 | Vulnerable | The Libreswan Project |
- cpe:2.3:a:libreswan:libreswan:*:*:*:*:*:*:*:* Versions before 5.3.1 Vulnerable ·The Libreswan Project
Remediation
- Fix · CNA libreswan (The Libreswan Project) Fixed in 5.3.1
Red Hat 14 advisories
- RHSA-2026:84887 Released 2026-10-19 · Red Hat rating Moderatelibreswan security update
- Red Hat Enterprise Linux AppStream AUS (v.8.4) libreswan-4.3-6.el8_4.2
- Red Hat Enterprise Linux AppStream EUS EXTENSION (v.8.4) libreswan-4.3-6.el8_4.2
- RHSA-2026:82154 Released 2026-10-13 · Red Hat rating Moderatelibreswan security update
- Red Hat Enterprise Linux AppStream AUS (v.8.6) libreswan-4.5-1.el8_6.6
- Red Hat Enterprise Linux AppStream EUS EXTENSION (v.8.6) libreswan-4.5-1.el8_6.6
- RHSA-2026:72287 Released 2026-09-28 · Red Hat rating Importantlibreswan security update
- Red Hat Enterprise Linux AppStream E4S (v.8.8) libreswan-4.9-3.el8_8.3
- Red Hat Enterprise Linux AppStream TUS (v.8.8) libreswan-4.9-3.el8_8.3
Show 11 more Red Hat advisories
- RHSA-2026:63044 Released 2026-09-09 · Red Hat rating ImportantOpenShift Container Platform 4.19.46 bug fix and security update
- Red Hat OpenShift Container Platform 4.19 rhcos-aarch64-4.19.9.6.202609021231-0, rhcos-ppc64le-4.19.9.6.202609021231-0, rhcos-s390x-4.19.9.6.202609021231-0 +1
- RHSA-2026:63041 Released 2026-09-08 · Red Hat rating ImportantOpenShift Container Platform 4.21.32 bug fix and security update
- Red Hat OpenShift Container Platform 4.21 rhcos-aarch64-4.21.9.6.202609021100-0, rhcos-ppc64le-4.21.9.6.202609021100-0, rhcos-s390x-4.21.9.6.202609021100-0 +1
- RHSA-2026:63100 Released 2026-09-08 · Red Hat rating ImportantOpenShift Container Platform 4.20.37 bug fix and security update
- Red Hat OpenShift Container Platform 4.20 rhcos-aarch64-4.20.9.6.202609021029-0, rhcos-ppc64le-4.20.9.6.202609021029-0, rhcos-s390x-4.20.9.6.202609021029-0 +1
- RHSA-2026:61779 Released 2026-08-31 · Red Hat rating Importantlibreswan security update
- Red Hat Enterprise Linux AppStream E4S (v.9.2) libreswan-4.9-5.el9_2.5
- RHSA-2026:61258 Released 2026-08-31 · Red Hat rating Importantlibreswan security update
- Red Hat Enterprise Linux AppStream E4S (v.9.4) libreswan-4.12-3.el9_4.2
- RHSA-2026:57741 Released 2026-08-20 · Red Hat rating Importantlibreswan security update
- Red Hat Enterprise Linux AppStream EUS (v.9.6) libreswan-4.15-8.el9_6.1
- RHSA-2026:55449 Released 2026-08-17 · Red Hat rating Importantlibreswan security update
- Red Hat Enterprise Linux AppStream EUS (v. 10.0) libreswan-5.2-1.el10_0.5
- RHSA-2026:46986 Released 2026-07-27 · Red Hat rating Importantlibreswan security update
- Fast Datapath for Red Hat Enterprise Linux 9 libreswan-5.3.2-1.el9fdp
- RHSA-2026:46398 Released 2026-07-27 · Red Hat rating Importantlibreswan security update
- Red Hat Enterprise Linux AppStream (v. 10) libreswan-5.3.2-1.el10_2, libreswan-minimal-5.3.2-1.el10_2
- RHSA-2026:46397 Released 2026-07-27 · Red Hat rating Importantlibreswan security update
- Red Hat Enterprise Linux AppStream (v. 9) libreswan-4.15-10.el9_8
- RHSA-2026:46396 Released 2026-07-27 · Red Hat rating Importantlibreswan security update
- Red Hat Enterprise Linux AppStream (v. 8) libreswan-4.12-2.el8_10.6
Vendor assessments
Red Hat
Red Hat rating: Moderate. Red Hat's page for this CVE →
| Product | Status | Plan or fix |
|---|---|---|
| Red Hat Enterprise Linux 6 | Affected | No fix planned: Out of support scope |
| Red Hat Enterprise Linux 7 | Affected | No fix yet |
| Red Hat OpenShift Container Platform 5 | Affected | No fix yet |
| Fast Datapath for Red Hat Enterprise Linux 9 | Fixed | RHSA-2026:46986 |
| Red Hat Enterprise Linux AppStream (v. 10) | Fixed | RHSA-2026:46398 |
| Red Hat Enterprise Linux AppStream (v. 8) | Fixed | RHSA-2026:46396 |
| Red Hat Enterprise Linux AppStream (v. 9) | Fixed | RHSA-2026:46397 |
| Red Hat Enterprise Linux AppStream AUS (v.8.4) | Fixed | RHSA-2026:84887 |
| Red Hat Enterprise Linux AppStream AUS (v.8.6) | Fixed | RHSA-2026:82154 |
| Red Hat Enterprise Linux AppStream E4S (v.8.8) | Fixed | RHSA-2026:72287 |
| Red Hat Enterprise Linux AppStream E4S (v.9.2) | Fixed | RHSA-2026:61779 |
| Red Hat Enterprise Linux AppStream E4S (v.9.4) | Fixed | RHSA-2026:61258 |
| Red Hat Enterprise Linux AppStream EUS (v. 10.0) | Fixed | RHSA-2026:55449 |
| Red Hat Enterprise Linux AppStream EUS (v.9.6) | Fixed | RHSA-2026:57741 |
| Red Hat Enterprise Linux AppStream EUS EXTENSION (v.8.4) | Fixed | RHSA-2026:84887 |
| Red Hat Enterprise Linux AppStream EUS EXTENSION (v.8.6) | Fixed | RHSA-2026:82154 |
| Red Hat Enterprise Linux AppStream TUS (v.8.8) | Fixed | RHSA-2026:72287 |
| Red Hat OpenShift Container Platform 4.19 | Fixed | RHSA-2026:63044 |
| Red Hat OpenShift Container Platform 4.20 | Fixed | RHSA-2026:63100 |
| Red Hat OpenShift Container Platform 4.21 | Fixed | RHSA-2026:63041 |
Not affected: 11 products
- Red Hat Enterprise Linux AppStream AUS (v.8.4)
- Red Hat Enterprise Linux AppStream AUS (v.8.6)
- Red Hat Enterprise Linux AppStream E4S (v.8.8)
- Red Hat Enterprise Linux AppStream E4S (v.9.2)
- Red Hat Enterprise Linux AppStream E4S (v.9.4)
- Red Hat Enterprise Linux AppStream EUS (v. 10.0)
- Red Hat Enterprise Linux AppStream EUS (v.9.6)
- Red Hat Enterprise Linux AppStream EUS EXTENSION (v.8.4)
- Red Hat Enterprise Linux AppStream EUS EXTENSION (v.8.6)
- Red Hat Enterprise Linux AppStream TUS (v.8.8)
- Red Hat OpenShift Container Platform 4
Timeline
- 2026-10-02 Threatist record created from CVE-2026-50722
- 2026-10-03 Alias added: GHSA-h4cv-5vw8-2p6m
- 2026-10-13 Fix available: Red Hat Enterprise Linux AppStream AUS (v.8.6), Red Hat Enterprise Linux AppStream EUS EXTENSION (v.8.6) · Red Hat
- 2026-10-14 Fix available: RHSA-2026:82154 · Red Hat
- 2026-10-20 Fix available: RHSA-2026:84887 · Red Hat
- 2026-10-20 Fix available: Red Hat Enterprise Linux AppStream AUS (v.8.4), Red Hat Enterprise Linux AppStream EUS EXTENSION (v.8.4) · Red Hat
- 2026-11-06 Affected versions changed · Red Hat
References
More The Libreswan Project Libreswan vulnerabilities
- TI-2023-09114 Libreswan 4.9 allows remote attackers to cause a denial of service (assert failure and… CVSS 3.1MEDIUM 6.5
- TI-2013-05949 Race condition in the libreswan.spec files for Red Hat Enterprise Linux (RHEL) and Fedora… CVSS 2.0HIGH 9.3
- TI-2023-02152 Uncontrolled resource consumption in libreswan CVSS 3.1HIGH 7.5
- TI-2026-37394 IKEv1 Denial of Service via RSA-SHA1 (PKCS#1 Version 1.5 Encrypted) authentication payload CVSS 3.1HIGH 8.1
- TI-2023-14401 pluto in Libreswan before 4.11 allows a denial of service (responder SPI mishandling and… CVSS 3.1HIGH 7.5
- TI-2026-10657 IKEv2 Denial of Service via malformed fragmentation CVSS 3.1HIGH 7.5
Sources
- CVE-2026-50722 · CVE Program
- CVE-2026-50722 · NVD
- FIRST EPSS
- GHSA-h4cv-5vw8-2p6m · GitHub Advisory Database · CC BY 4.0
- CVE-2026-50722 · Red Hat security data · CC BY 4.0
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