VulnerabilityPublished 28 Oct 2026

CVE-2026-99165: Linux kernel · sctp: revalidate output stream after association connect wait

Affects Linux kernelSource CVE Database V5

Not known to be exploited · fixed in fd56ac95ec31a05b66e8938debfa847f49c0e993 : update Linux kernel when convenient.

Data as of 28 Oct 2026, 10:58 UTC

Severity

Unrated

Rated by Threat Radar · CVSS not yet scored by NVD

Patch: Available – fixed in fd56ac95ec31a05b66e8938debfa847f49c0e993, b7ad72414c673ce1fa1f463e807cd4f34f8be9bf, 77a63d1b813b08c4e5a948f5e04fbaca6176aa8f

Exploitation evidence

Disclosed: evidence found.
CVE published 28 Oct 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponised: Public exploit code exists in Metasploit or Exploit-DB, or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Upgrade Linux kernel to fd56ac95ec31a05b66e8938debfa847f49c0e993, b7ad72414c673ce1fa1f463e807cd4f34f8be9bf or 77a63d1b813b08c4e5a948f5e04fbaca6176aa8f.

Affected software

Product	Affected	Fixed in
LinuxLinux	Affected ≥ 668c9beb9020d5834ee9e43c208190a07d2b1928, < fd56ac95ec31a05b66e8938debfa847f49c0e993	Fixed in fd56ac95ec31a05b66e8938debfa847f49c0e993
LinuxLinux	Affected ≥ 668c9beb9020d5834ee9e43c208190a07d2b1928, < b7ad72414c673ce1fa1f463e807cd4f34f8be9bf	Fixed in b7ad72414c673ce1fa1f463e807cd4f34f8be9bf
LinuxLinux	Affected ≥ 668c9beb9020d5834ee9e43c208190a07d2b1928, < 77a63d1b813b08c4e5a948f5e04fbaca6176aa8f	Fixed in 77a63d1b813b08c4e5a948f5e04fbaca6176aa8f
LinuxLinux	Affected =4.16	Fixed in–
Debiandebian/linux`pkg:deb/debian/linux`Other threats	Affected =4.16	Fixed in–

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

Description

In the Linux kernel, the following vulnerability has been resolved: sctp: revalidate output stream after association connect wait When message interleaving is enabled, the first send waits for association establishment before building its data chunks. The wait drops the socket lock, and handshake processing can reduce the output stream count to the peer-advertised inbound stream count. sctp_stream_init() then frees the extension of every removed stream. The sender resumes with the stream that it checked before the wait. If the peer removed that stream, sctp_outq_tail() later dereferences its NULL extension. Fatal-oops policies then panic the host. KASAN: null-ptr-deref in range [0x38-0x3f] RIP: sctp_outq_tail+0x49e/0xaa0 Call Trace: sctp_primitive_SEND sctp_sendmsg_to_asoc sctp_sendmsg A range check alone is insufficient. Stream reconfiguration can grow the output count again while the lock is released without recreating extensions freed by the earlier shrink. The stream can then be in range while its extension remains NULL. The send-buffer wait has the same issue. Factor the range and extension checks into a helper and repeat both after each send-path wait that drops the socket lock. Once the lock is reacquired, the validation remains stable through data creation and queueing. If validation fails after the connect wait, the auto-created association is already established. Return ESRCH so the existing caller path keeps it under state-machine ownership instead of freeing it directly, which would leave protocol, counter and socket state inconsistent.

References

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