EUVD-2026-39200
GHSA-r3wj-w7v3-6mqq
Severity by source
AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Local unprivileged access required (AV:L/PR:L); network must forward SSRR/LSRR packets (AC:H); scope changes as packets leave to attacker-controlled external node (S:C); TCP ISN leakage is confidentiality impact (C:H), no availability impact.
Primary rating from NVD.
CVSS VectorNVD
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Lifecycle Timeline
5DescriptionNVD
In the Linux kernel, the following vulnerability has been resolved:
ipv4: restrict IPOPT_SSRR and IPOPT_LSRR options
This patch restricts setting Loose Source and Record Route (LSRR) and Strict Source and Record Route (SSRR) IP options to users with CAP_NET_RAW capability.
This prevents unprivileged applications from forcing packets to route through attacker-controlled nodes to leak TCP ISN and possibly other protocol information.
While LSRR and SSRR are commonly filtered in many network environments, they may still be supported and forwarded along some network paths.
RFC 7126 (Recommendations on Filtering of IPv4 Packets Containing IPv4 Options) recommend to drop these options in 4.3 and 4.4.
AnalysisAI
Unprivileged local users on Linux systems running unpatched kernels can set IPOPT_SSRR (Strict Source and Record Route) and IPOPT_LSRR (Loose Source and Record Route) IPv4 options without the CAP_NET_RAW capability, enabling them to force outbound packets through attacker-controlled network nodes and leak TCP Initial Sequence Numbers (ISN) along with other protocol metadata. Affected systems span Linux kernel versions from 2.6.12 through multiple stable branches prior to their respective patch releases. …
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Attack ChainAIDerived
Hypothetical attack flow derived from CVE metadata
Vulnerability AssessmentAI
| Exploitation | Exploitation requires a local unprivileged user account (PR:L per CVSS) with the ability to create sockets - standard on any multi-user Linux system. … Additional conditions and limiting factors are described in the full assessment. |
| Risk Assessment | Real-world risk is moderate-to-low despite the information disclosure potential. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in. |
| Exploit Scenario | A local unprivileged user on a shared Linux host creates a raw socket and sets IPOPT_LSRR to route outbound TCP connections through an attacker-controlled intermediate hop (e.g., a VPS or compromised router on a path the network forwards). The intermediate node observes the TCP ISN in the SYN packet, which can be used to infer sequence number patterns and potentially facilitate blind TCP session injection against third-party connections originating from the same host. … |
| Remediation | Upgrade to a patched stable kernel release: 5.10.259, 5.15.210, 6.1.176, 6.6.143, 6.12.94, 6.18.36, 7.0.13, or 7.1, depending on the active kernel series. … Detailed patch versions, workarounds, and compensating controls in full report. |
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External POC / Exploit Code
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