fkie_cve-2025-39797
Vulnerability from fkie_nvd
Published
2025-09-12 16:15
Modified
2025-09-15 15:21
Severity ?
Summary
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.
References
Impacted products
| Vendor | Product | Version |
|---|
{
"cveTags": [],
"descriptions": [
{
"lang": "en",
"value": "In the Linux kernel, the following vulnerability has been resolved:\n\nxfrm: Duplicate SPI Handling\n\nThe issue originates when Strongswan initiates an XFRM_MSG_ALLOCSPI\nNetlink message, which triggers the kernel function xfrm_alloc_spi().\nThis function is expected to ensure uniqueness of the Security Parameter\nIndex (SPI) for inbound Security Associations (SAs). However, it can\nreturn success even when the requested SPI is already in use, leading\nto duplicate SPIs assigned to multiple inbound SAs, differentiated\nonly by their destination addresses.\n\nThis behavior causes inconsistencies during SPI lookups for inbound packets.\nSince the lookup may return an arbitrary SA among those with the same SPI,\npacket processing can fail, resulting in packet drops.\n\nAccording to RFC 4301 section 4.4.2 , for inbound processing a unicast SA\nis uniquely identified by the SPI and optionally protocol.\n\nReproducing the Issue Reliably:\nTo consistently reproduce the problem, restrict the available SPI range in\ncharon.conf : spi_min = 0x10000000 spi_max = 0x10000002\nThis limits the system to only 2 usable SPI values.\nNext, create more than 2 Child SA. each using unique pair of src/dst address.\nAs soon as the 3rd Child SA is initiated, it will be assigned a duplicate\nSPI, since the SPI pool is already exhausted.\nWith a narrow SPI range, the issue is consistently reproducible.\nWith a broader/default range, it becomes rare and unpredictable.\n\nCurrent implementation:\nxfrm_spi_hash() lookup function computes hash using daddr, proto, and family.\nSo if two SAs have the same SPI but different destination addresses, then\nthey will:\na. Hash into different buckets\nb. Be stored in different linked lists (byspi + h)\nc. Not be seen in the same hlist_for_each_entry_rcu() iteration.\nAs a result, the lookup will result in NULL and kernel allows that Duplicate SPI\n\nProposed Change:\nxfrm_state_lookup_spi_proto() does a truly global search - across all states,\nregardless of hash bucket and matches SPI and proto."
}
],
"id": "CVE-2025-39797",
"lastModified": "2025-09-15T15:21:42.937",
"metrics": {},
"published": "2025-09-12T16:15:34.137",
"references": [
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"url": "https://git.kernel.org/stable/c/29e9158f91f99057dbd35db5e8674d93b38549fe"
},
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"url": "https://git.kernel.org/stable/c/2fc5b54368a1bf1d2d74b4d3b8eea5309a653e38"
},
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"url": "https://git.kernel.org/stable/c/3d8090bb53424432fa788fe9a49e8ceca74f0544"
},
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"url": "https://git.kernel.org/stable/c/94f39804d891cffe4ce17737d295f3b195bc7299"
},
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"url": "https://git.kernel.org/stable/c/c67d4e7a8f90fb6361ca89d4d5c9a28f4e935e47"
}
],
"sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"vulnStatus": "Awaiting Analysis"
}
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Sightings
| Author | Source | Type | Date |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or seen somewhere by the user.
- Confirmed: The vulnerability is confirmed from an analyst perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: This vulnerability was exploited and seen by the user reporting the sighting.
- Patched: This vulnerability was successfully patched by the user reporting the sighting.
- Not exploited: This vulnerability was not exploited or seen by the user reporting the sighting.
- Not confirmed: The user expresses doubt about the veracity of the vulnerability.
- Not patched: This vulnerability was not successfully patched by the user reporting the sighting.
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