CVE-2026-64046: net: tls: prevent chain-after-chain in plain text SG
In the Linux kernel, the following vulnerability has been resolved:
net: tls: prevent chain-after-chain in plain text SG
Sashiko points out that if end = 0 (start != 0) the current
code will create a chain link to content type right after
the wrap link:
This would create a chain where the wrap link points directly
to another chain link. The scatterlist API sg_next iterator
does not recursively resolve consecutive chain links.
meaning this is illegal input to crypto.
The wrapping link is unnecessary if end = 0. end is the entry after
the last one used so end = 0 means there's nothing pushed after
the wrap:
end start i
v v v
[ ]...[ ][ d ][ d ][ d ][ d ][rsv for wrap]
Skip the wrapping in this case.
TLS 1.3 can use the "wrapping slot" for it's chaining if end = 0.
This avoids the chain-after-chain.
Move the wrap chaining before marking END and chaining off content
type, that feels like more logical ordering to me, but should not
matter from functional perspective.
Security readout for executives and security teams
Plain-English summary
This is a critical Linux kernel networking/TLS flaw. The reported bug can feed malformed scatterlist structure into kernel crypto handling. The source bundle shows upstream stable fixes, but does not show active exploitation, affected distributions, or a named workaround.
Executive priority
Prioritize remediation as urgent because the CVSS is 9.8 and the flaw is in kernel networking/TLS handling. Focus first on critical Linux infrastructure, internet-facing systems, and platforms where delayed kernel patching creates broad operational risk.
Technical view
In net/tls, when end equals 0 and start is nonzero, code can create consecutive scatterlist chain links. The scatterlist iterator does not recursively resolve that shape, making it illegal input to crypto. Fixes skip unnecessary wrapping and adjust chaining order.
Likely exposure
Exposure is likely limited to systems running affected Linux kernel versions where the kernel TLS path is reachable or used. The bundle lists affected Linux kernel ranges, but not distribution package names, appliances, or required runtime configuration.
Exploitation context
The CVSS vector is network, low complexity, unauthenticated, and no user interaction. However, the bundle marks KEV false and provides no proof-of-concept, exploitation report, or operational exploit details. Active exploitation should not be assumed.
Researcher notes
Evidence is mostly from the CVE text and upstream stable commits. The bundle does not provide a crash reproducer, exploitability analysis, impacted distributions, or confirmation of real-world attacks. Validation should focus on affected kernel lineage and patch presence.
Mitigation direction
Update affected Linux kernels to vendor or upstream stable releases containing the referenced fixes.
Check Linux distribution advisories for backported packages and reboot requirements.
Prioritize externally exposed servers and systems using kernel TLS features.
If no package is available, follow vendor guidance for temporary risk reduction.
Validation and detection
Inventory Linux kernel versions across servers, containers hosts, and appliances.
Compare running kernels against vendor advisories and the affected version ranges in the CVE record.
Verify installed kernel packages include the relevant stable fix or vendor backport.
Confirm systems have rebooted into the fixed kernel after patch installation.
Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.
Potential ATT&CK relevance
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CVE-2026-64046 mapping review
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1CVSS vectors
3Timeline events
0ADP providers
9Source links
CVSS vector scores
1 official score
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