Answer in brief
CVE-2026-63913 records a Unknown severity vulnerability in netfilter: conntrack: tcp: do not force CLOSE on invalid-seq RST without direction check. The current sources do not mark it as known exploited. The current feed maps Linux/Linux (generic), Linux/Linux (generic). Check affected ranges and fixed versions before updating.
Analysis pending evidence review
HOL Guard separates source facts from reviewed analysis. See the methodology.
Answer in brief
CVE-2026-63913 records a Unknown severity vulnerability in netfilter: conntrack: tcp: do not force CLOSE on invalid-seq RST without direction check. The current sources do not mark it as known exploited. The current feed maps Linux/Linux (generic), Linux/Linux (generic). Check affected ranges and fixed versions before updating.
Analysis pending evidence review
HOL Guard separates source facts from reviewed analysis. See the methodology.
A CVSS score is not reported in the current record. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.
Analysis status
Analysis pending evidence review
Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.
The current feed maps Linux/Linux (generic), Linux/Linux (generic). Check affected ranges and fixed versions before updating.
| Package | Affected range | Fixed version |
|---|---|---|
| Linux/Linuxgeneric | >=9fb9cbb1082d6b31fb45aa1a14432449a0df6cf1 <2006979a15af5404bf932a325357683c0bac1656 || >=9fb9cbb1082d6b31fb45aa1a14432449a0df6cf1 <6476c17d536dbd321c073242e762ddb2713a1238 || >=9fb9cbb1082d6b31fb45aa1a14432449a0df6cf1 <f5547bebc416d56f56fb5b86dc20aabfa42165a0 || >=9fb9cbb1082d6b31fb45aa1a14432449a0df6cf1 <2bb6d82b586ea5a4cb73bbdd6b7432e96096bc77 || >=9fb9cbb1082d6b31fb45aa1a14432449a0df6cf1 <f206def4e86d810f927ba1d8e322ea72b29bce58 || >=9fb9cbb1082d6b31fb45aa1a14432449a0df6cf1 <b98ab51c45c5608a1c19ce7fd17a3032469bb83f || >=9fb9cbb1082d6b31fb45aa1a14432449a0df6cf1 <d67c6adee8d1b65330d0174c4c367faba14e80a8 || >=9fb9cbb1082d6b31fb45aa1a14432449a0df6cf1 <bed6e04be8e6b9133d8b16d5a42d0e0ce674fa9a | 2006979a15af5404bf932a325357683c0bac1656, 6476c17d536dbd321c073242e762ddb2713a1238, f5547bebc416d56f56fb5b86dc20aabfa42165a0, 2bb6d82b586ea5a4cb73bbdd6b7432e96096bc77, f206def4e86d810f927ba1d8e322ea72b29bce58, b98ab51c45c5608a1c19ce7fd17a3032469bb83f, d67c6adee8d1b65330d0174c4c367faba14e80a8, bed6e04be8e6b9133d8b16d5a42d0e0ce674fa9a |
| Linux/Linuxgeneric | 2.6.15 | Not reported |
Published upstream
Jul 19, 2026
Evidence: source:cvelist:source_dates:source-dates:recordSource modified
Aug 5, 2026
Evidence: source:cvelist:source_dates:source-dates:recordFirst seen by HOL
Aug 5, 2026
In the Linux kernel, the following vulnerability has been resolved: netfilter: conntrack: tcp: do not force CLOSE on invalid-seq RST without direction check An unintended behavior in the TCP conntrack state machine allows a connection to be forced into the CLOSE state using an RST packet with an invalid sequence number. Specifically, after a SYN packet is observed, an RST with an invalid SEQ can transition the conntrack entry to TCP_CONNTRACK_CLOSE, regardless of whether the RST corresponds to the expected reply direction. The relevant code path assumes the RST is a response to an outgoing SYN, but does not validate packet direction or ensure that a matching SYN was actually sent in the opposite direction. As a result, a crafted packet sequence consisting of a SYN followed by an invalid-sequence RST can prematurely terminate an active NAT entry. This makes connection teardown easier than intended. So, tighten the state transition logic to ensure that RST-triggered CLOSE transitions only occur when the RST is a valid response to a previously observed SYN in the correct direction.
Quoted source text, attributed separately from HOL analysis.
A CVSS score is not reported in the current record. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.
Analysis status
Analysis pending evidence review
Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.
The current feed maps Linux/Linux (generic), Linux/Linux (generic). Check affected ranges and fixed versions before updating.
| Package | Affected range | Fixed version |
|---|---|---|
| Linux/Linuxgeneric | >=9fb9cbb1082d6b31fb45aa1a14432449a0df6cf1 <2006979a15af5404bf932a325357683c0bac1656 || >=9fb9cbb1082d6b31fb45aa1a14432449a0df6cf1 <6476c17d536dbd321c073242e762ddb2713a1238 || >=9fb9cbb1082d6b31fb45aa1a14432449a0df6cf1 <f5547bebc416d56f56fb5b86dc20aabfa42165a0 || >=9fb9cbb1082d6b31fb45aa1a14432449a0df6cf1 <2bb6d82b586ea5a4cb73bbdd6b7432e96096bc77 || >=9fb9cbb1082d6b31fb45aa1a14432449a0df6cf1 <f206def4e86d810f927ba1d8e322ea72b29bce58 || >=9fb9cbb1082d6b31fb45aa1a14432449a0df6cf1 <b98ab51c45c5608a1c19ce7fd17a3032469bb83f || >=9fb9cbb1082d6b31fb45aa1a14432449a0df6cf1 <d67c6adee8d1b65330d0174c4c367faba14e80a8 || >=9fb9cbb1082d6b31fb45aa1a14432449a0df6cf1 <bed6e04be8e6b9133d8b16d5a42d0e0ce674fa9a | 2006979a15af5404bf932a325357683c0bac1656, 6476c17d536dbd321c073242e762ddb2713a1238, f5547bebc416d56f56fb5b86dc20aabfa42165a0, 2bb6d82b586ea5a4cb73bbdd6b7432e96096bc77, f206def4e86d810f927ba1d8e322ea72b29bce58, b98ab51c45c5608a1c19ce7fd17a3032469bb83f, d67c6adee8d1b65330d0174c4c367faba14e80a8, bed6e04be8e6b9133d8b16d5a42d0e0ce674fa9a |
| Linux/Linuxgeneric | 2.6.15 | Not reported |
Published upstream
Jul 19, 2026
Evidence: source:cvelist:source_dates:source-dates:recordSource modified
Aug 5, 2026
Evidence: source:cvelist:source_dates:source-dates:recordFirst seen by HOL
Aug 5, 2026
In the Linux kernel, the following vulnerability has been resolved: netfilter: conntrack: tcp: do not force CLOSE on invalid-seq RST without direction check An unintended behavior in the TCP conntrack state machine allows a connection to be forced into the CLOSE state using an RST packet with an invalid sequence number. Specifically, after a SYN packet is observed, an RST with an invalid SEQ can transition the conntrack entry to TCP_CONNTRACK_CLOSE, regardless of whether the RST corresponds to the expected reply direction. The relevant code path assumes the RST is a response to an outgoing SYN, but does not validate packet direction or ensure that a matching SYN was actually sent in the opposite direction. As a result, a crafted packet sequence consisting of a SYN followed by an invalid-sequence RST can prematurely terminate an active NAT entry. This makes connection teardown easier than intended. So, tighten the state transition logic to ensure that RST-triggered CLOSE transitions only occur when the RST is a valid response to a previously observed SYN in the correct direction.
Quoted source text, attributed separately from HOL analysis.