netfilter: conntrack: tcp: use UNACK timeout for non-closing RST packets
Summary
| CVE | CVE-2026-99283 |
|---|---|
| State | PUBLISHED |
| Assigner | Linux |
| Source Priority | CVE Program / NVD first with legacy fallback |
| Published | 2026-11-07 21:17:00 UTC |
| Updated | 2026-11-10 19:22:31 UTC |
| Description | In the Linux kernel, the following vulnerability has been resolved: netfilter: conntrack: tcp: use UNACK timeout for non-closing RST packets Commit be0502a3f2e9 ("netfilter: conntrack: tcp: only close if RST matches exact sequence") keeps an established conntrack entry in ESTABLISHED when an in-window RST does not match the expected sequence number exactly, so the endpoint can validate the RST with a challenge ACK. The timeout selection nevertheless uses the CLOSE timeout for every RST packet. The bug is that timeout selection is based on the packet type, not on the state transition result: even when RST validation keeps new_state in ESTABLISHED, the timeout is still forced to TCP_CONNTRACK_CLOSE. Linux TCP independently rate limits challenge ACKs per socket. A second non-exact RST can therefore arrive after the first challenge ACK has restored the timeout but before the rate limit expires. The second RST lowers the timeout to 10 seconds again while the endpoint suppresses the second challenge ACK, allowing the conntrack entry to expire while both TCP endpoints remain established. Using the ESTABLISHED timeout for such RSTs would avoid this short expiration window, but it could also retain stale entries for the five-day default because conntrack cannot reliably match the endpoint's exact TCP state. Use the UNACK timeout for RST packets that leave the conntrack entry in TCP_CONNTRACK_ESTABLISHED. Exact-match RSTs and accepted RST packet trains still fall through to timeouts[new_state], which preserves the CLOSE timeout when conntrack accepts the RST as closing the flow. This avoids the aggressive 10-second expiration window for non-exact RSTs while preserving the short timeout for RSTs that conntrack accepts as closing the flow. |
Risk And Classification
EPSS: 0.001940000 probability, percentile 0.091390000 (date 2026-11-10)
Vendor Declared Affected Products
| Source | Vendor | Product | Version | Platforms |
|---|---|---|---|---|
| CNA | Linux | Linux | affected 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 4d39a039d0b7737f8475c2431f18572b3b186a3b git | Not specified |
| CNA | Linux | Linux | affected 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 0c6d33329960b2d884a399196c8403643d8a9de6 git | Not specified |
| CNA | Linux | Linux | affected 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 bf80e6802273a900311b44e47c9b1a59c6d2473c git | Not specified |
| CNA | Linux | Linux | affected 6.12.117 semver | Not specified |
| CNA | Linux | Linux | affected 6.18.61 semver | Not specified |
| CNA | Linux | Linux | unaffected 6.12.117 6.12.* semver | Not specified |
| CNA | Linux | Linux | unaffected 6.18.61 6.18.* semver | Not specified |
| CNA | Linux | Linux | unaffected 7.3 * original_commit_for_fix | Not specified |
References
| Reference | Source | Link | Tags |
|---|---|---|---|
| git.kernel.org/stable/c/bf80e6802273a900311b44e47c9b1a59c6d2473c | 416baaa9-dc9f-4396-8d5f-8c081fb06d67 | git.kernel.org | |
| git.kernel.org/stable/c/4d39a039d0b7737f8475c2431f18572b3b186a3b | 416baaa9-dc9f-4396-8d5f-8c081fb06d67 | git.kernel.org | |
| git.kernel.org/stable/c/0c6d33329960b2d884a399196c8403643d8a9de6 | 416baaa9-dc9f-4396-8d5f-8c081fb06d67 | git.kernel.org | |
| CVE Program record | CVE.ORG | www.cve.org | canonical |
| NVD vulnerability detail | NVD | nvd.nist.gov | canonical, analysis |
No vendor comments have been submitted for this CVE.
There are currently no legacy QID mappings associated with this CVE.