CVE-2025-39797None▾ SunlitIn 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(). …
▾ Sunlit zone — Low / medium · no exploitation signal
impact 2.8 · likelihood 0 · exploitation 0
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Stakeholder-Specific Vulnerability Categorization from CISA's ADP record at CVE.org: whether exploitation is observed, whether an attack can be automated, and how much of the system is at stake.
Exploit-prediction probability, daily snapshots since Nov 3.
Disclosure to exploitation, from the record and what we observed since indexing it.
Disclosed via CVEORG
0.2%
Last analysed / modified upstream
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 3rd Child SA is initiated, it will be assigned a duplicate SPI, since the SPI pool is already exhausted. With a narrow SPI range, the issue is consistently reproducible. With a broader/default range, it becomes rare and unpredictable.
Current implementation: xfrm_spi_hash() lookup function computes hash using daddr, proto, and family. So if two SAs have the same SPI but different destination addresses, then they will: a. Hash into different buckets b. Be stored in different linked lists (byspi + h) c. Not be seen in the same hlist_for_each_entry_rcu() iteration. As a result, the lookup will result in NULL and kernel allows that Duplicate SPI
Proposed Change: xfrm_state_lookup_spi_proto() does a truly global search - across all states, regardless of hash bucket and matches SPI and proto.
Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 < fb58962aa3b9359988c7b5b15a971fd9ad5b0ecdLinux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 < 3d8090bb53424432fa788fe9a49e8ceca74f0544Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 < 2fc5b54368a1bf1d2d74b4d3b8eea5309a653e38Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 < c67d4e7a8f90fb6361ca89d4d5c9a28f4e935e47Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 < 29e9158f91f99057dbd35db5e8674d93b38549feLinux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 < 94f39804d891cffe4ce17737d295f3b195bc7299Linux 2.6.12Refer to the linked advisories for vendor-supplied fixes and affected version ranges.
Connected by shared product, vendor, weakness, or advisory.
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