CVE intelligence and bounded remediation

CVE-2025-39797 — Linux Linux Kernel security vulnerability

High CVSS 7.8

In the Linux kernel, the following vulnerability has been resolved: xfrm: Duplicate SPI Handling The issue originates when Strongswan initiates an XFRM_MSG_ALLOCSPI Netlink message, which triggers the kernel function xfrm_alloc_spi(). This function is expected to ensure uniqueness of the Security Parameter Index (SPI) for inbound Security Associations (SAs). However, it can return success even when the requested SPI is already in use, leading to duplicate SPIs assigned to multiple inbound SAs, differentiated only by their destination addresses. This behavior causes inconsistencies during SPI lookups for inbound packets. Since the lookup may return an arbitrary SA among those with the same SPI, packet processing can fail, resulting in packet drops. According to RFC 4301 section 4.4.2 , for inbound processing a unicast SA is uniquely identified by the SPI and optionally protocol. Reproducing the Issue Reliably: To consistently reproduce the problem, restrict the available SPI range in charon.conf : spi_min = 0x10000000 spi_max = 0x10000002 This limits the system to only 2 usable SPI values. Next, create more than 2 Child SA. each using unique pair of src/dst address. As soon as the…

Severity
High
CVSS
7.8 (3.1)
Published
2025-09-12
CISA KEV
Not currently listed
Ecosystem
linux/kernel

Affected products

  • linux / linux_kernel

Showing 1 representative product identities from 4 source matches. Confirm exact affected versions with the linked vendor and NVD evidence.

Matched remediation archetype

General vulnerability remediation

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Check exposure

  • Confirm the affected component, deployment paths, reachable interfaces, and enabled features from inventories and configuration, without probing production destructively.
  • Compare the advisory's affected conditions with the repository lockfiles, build manifests, artifacts, and runtime inventory.
  • Identify data sensitivity, trust boundaries, and privilege level for every confirmed affected deployment.

Remediate safely

  • Apply a vendor-supported fix or remove the affected component or feature; record the selected change and its source in the repository.
  • Update direct and transitive dependency locks, generated artifacts, deployment manifests, and asset inventories together.
  • Add a regression test for the documented unsafe condition using inert inputs and preserve rollback instructions.

Authoritative sources

Complete CVE record and remediation plan

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